Medical School · Year 2 · Endocrine · includes a quiz and discussion video

Lecture 13: Diabetes Mellitus - Management

Unit 2.3: Endocrine System

Learning Objectives

By the end of this lecture, students will be able to:

1. Describe the principles of glycemic management in diabetes
2. Explain insulin therapy including types and regimens
3. Describe oral and injectable non-insulin therapies for type 2 diabetes
4. Explain the management of diabetic ketoacidosis and hyperosmolar state
5. Describe the screening and management of chronic diabetic complications
6. Explain hypoglycemia recognition and management

Lecture Outline

I. Glycemic Targets

Effective diabetes management begins with establishing individualized glycemic targets that balance the benefits of tight glucose control against the risks of hypoglycemia and treatment burden. These targets are informed by clinical trial evidence demonstrating that improved glycemic control reduces microvascular complications, while recognizing that excessively aggressive targets in certain populations may cause harm. A patient-centered approach that considers multiple factors guides optimal target selection.

The cornerstone glycemic metric is HbA1c, which reflects average blood glucose over the preceding two to three months. For most adults with diabetes, an HbA1c target of less than 7% is appropriate, supported by landmark trials demonstrating reductions in microvascular disease at this threshold. Select patients with short disease duration, long life expectancy, and no significant cardiovascular disease may benefit from a more stringent target of less than 6.5%, provided this can be achieved without significant hypoglycemia. Conversely, older adults, those with multiple comorbidities, and patients at high risk for hypoglycemia are better served by a more relaxed target of less than 8% or an individualized goal. For patients with limited life expectancy, the focus shifts to avoiding symptomatic hyperglycemia rather than achieving any specific HbA1c number, with targets individualized to maximize comfort and quality of life.

Self-monitoring of blood glucose provides real-time feedback that complements HbA1c measurement. Preprandial (fasting) glucose targets are generally set at 80 to 130 mg/dL, while postprandial glucose measured two hours after the start of a meal should be less than 180 mg/dL. These targets allow patients on insulin to adjust their doses in response to current glucose levels and to identify patterns of hyper- or hypoglycemia that may not be captured by HbA1c alone.

Continuous glucose monitoring (CGM) has introduced the concept of time in range as an important glycemic metric. The target for time in range, defined as glucose between 70 and 180 mg/dL, is greater than 70% of the day. Equally important are the targets for time below range: less than 4% of time below 70 mg/dL and less than 1% of time below 54 mg/dL, reflecting the clinical significance of hypoglycemia prevention. Time above range, defined as glucose greater than 180 mg/dL, should be less than 25%. These CGM-derived metrics provide a more nuanced picture of glycemic control than HbA1c alone, capturing glycemic variability and hypoglycemia exposure.

Several patient-specific factors influence how aggressively glycemic targets should be set. Patients at high risk for hypoglycemia—including those with hypoglycemia unawareness, long-standing type 1 diabetes, or advanced age—warrant looser targets. Disease duration matters as well: stricter targets are more appropriate early in the disease course when the cumulative benefit of glucose control is greatest, while long-standing diabetes with established complications may favor more relaxed goals. Longer life expectancy supports stricter targets, as patients have more years to accrue the benefits of tight control. Comorbidities such as cardiovascular disease and chronic kidney disease should be considered in target setting. Ultimately, patient preference and shared decision-making are essential components, as the individual must weigh the daily burden of intensive management against the long-term benefits.

<image>Panel A: HbA1c goals by population showing less than 7% for most adults, less than 6.5% for select patients (short duration, long life expectancy), less than 8% for older adults with comorbidities or hypoglycemia risk, and individualized targets for limited life expectancy. Panel B: Self-monitoring blood glucose targets showing preprandial (fasting) goal of 80-130 mg/dL and postprandial (2-hour) goal of less than 180 mg/dL. Panel C: Continuous glucose monitoring time in range goals showing greater than 70% time in range (70-180 mg/dL), less than 4% below range (less than 70), less than 1% below 54, and less than 25% above range (greater than 180). Panel D: Factors influencing target individualization including hypoglycemia risk, disease duration, life expectancy, comorbidities (CVD, CKD), and patient preference through shared decision-making.</image>

II. Type 1 Diabetes Management

Type 1 diabetes is characterized by absolute insulin deficiency due to autoimmune destruction of pancreatic beta cells, meaning that exogenous insulin is essential for survival. Management centers on replicating physiologic insulin secretion as closely as possible through carefully designed insulin regimens, while leveraging technology such as insulin pumps and continuous glucose monitors to improve control and quality of life.

Patients with type 1 diabetes have an absolute requirement for insulin and cannot survive without it. The total daily insulin dose typically ranges from approximately 0.5 to 1 unit per kilogram per day, though this varies considerably based on activity level, insulin sensitivity, and other factors. This total dose is distributed between basal insulin, which accounts for approximately 40 to 50% and provides steady background coverage to suppress hepatic glucose output between meals and overnight, and bolus insulin, which accounts for approximately 50 to 60% and covers the glucose excursions associated with meals.

Understanding the pharmacokinetics of different insulin formulations is essential for designing effective regimens. Rapid-acting insulins, including lispro, aspart, and glulisine, have an onset of 10 to 15 minutes, peak at 1 to 2 hours, and last 3 to 5 hours, making them ideal for mealtime coverage. Short-acting regular insulin has a somewhat slower onset of 30 to 60 minutes, peaks at 2 to 4 hours, and has a duration of 5 to 8 hours. Intermediate-acting NPH insulin has an onset of 1 to 2 hours, a pronounced peak at 4 to 10 hours, and a duration of 12 to 18 hours. Long-acting insulins such as glargine and detemir have an onset of 1 to 2 hours, provide a relatively flat profile without a pronounced peak, and last 20 to 24 hours. Ultra-long-acting degludec similarly has a flat profile but extends its duration beyond 42 hours, offering even more stable basal coverage and dosing flexibility.

The basal-bolus regimen is the standard approach for type 1 diabetes management. This consists of a long-acting insulin administered once or twice daily to provide basal coverage, combined with a rapid-acting insulin administered before each meal to cover the anticipated carbohydrate intake. Additional correction doses of rapid-acting insulin are given when preprandial or postprandial glucose levels are above target, using an individualized correction factor (also known as an insulin sensitivity factor). This regimen offers substantial flexibility, allowing patients to adjust bolus doses based on meal composition and physical activity.

Insulin pump therapy, also known as continuous subcutaneous insulin infusion (CSII), represents an alternative to multiple daily injections. The pump delivers rapid-acting insulin continuously through a subcutaneous catheter, providing programmable basal rates that can be adjusted throughout the day to match circadian insulin requirements. Bolus doses are given at mealtimes and for glucose corrections through the pump's calculator. Benefits of pump therapy include improved glycemic control, greater lifestyle flexibility, and reduced frequency of hypoglycemia. However, pumps require significant cost, technical training, and attention to infusion site management, including regular site changes to prevent lipodystrophy and infection.

Continuous glucose monitoring measures interstitial glucose every five minutes, providing a near-continuous stream of data that transforms diabetes management. CGM systems generate high and low glucose alerts that warn patients of impending hypo- or hyperglycemia, as well as trend arrows that show the direction and rate of glucose change, enabling proactive rather than reactive management decisions. Perhaps the most transformative advance is the integration of CGM with insulin pumps in hybrid closed-loop systems, which use an algorithm to automatically adjust basal insulin delivery based on CGM readings. These automated insulin delivery systems significantly reduce time in hypoglycemia and hyperglycemia while increasing time in range, moving closer to the goal of an artificial pancreas.

<image>Panel A: Insulin types comparison table showing rapid-acting (lispro, aspart, glulisine; onset 10-15 min, peak 1-2 hr, duration 3-5 hr), short-acting (regular; 30-60 min onset), intermediate (NPH; 4-10 hr peak), long-acting (glargine, detemir; flat profile, 20-24 hr), and ultra-long (degludec; greater than 42 hr). Panel B: Basal-bolus regimen showing long-acting insulin once or twice daily for basal coverage (40-50% of total), rapid-acting before each meal for bolus coverage (50-60%), and correction doses for elevated glucose. Panel C: Insulin pump (CSII) showing continuous subcutaneous rapid-acting insulin delivery with programmable basal rates, bolus dosing for meals and corrections, and benefits of improved control and flexibility with reduced hypoglycemia. Panel D: Continuous glucose monitoring showing interstitial glucose measurement every 5 minutes, high and low glucose alarms, trend arrows showing direction of change, and integration with pumps in hybrid closed-loop systems for automated insulin delivery.</image>

III. Type 2 Diabetes - Lifestyle and Metformin

The foundation of type 2 diabetes management rests on lifestyle modifications and metformin therapy. Unlike type 1 diabetes, type 2 diabetes is characterized by insulin resistance and relative (rather than absolute) insulin deficiency, meaning that non-pharmacologic interventions can have a profound impact on disease trajectory. Metformin serves as the pharmacologic cornerstone for most patients, offering a favorable efficacy, safety, and cost profile.

Lifestyle modifications are the essential first step in type 2 diabetes management and should continue alongside all pharmacologic therapies. Weight loss of 5 to 7% of body weight has been demonstrated to significantly improve insulin sensitivity and glycemic control, and in the landmark Diabetes Prevention Program, intensive lifestyle intervention reduced the risk of developing type 2 diabetes by 58% in high-risk individuals. Dietary recommendations include caloric reduction to achieve and maintain a healthy weight, with patterns such as the Mediterranean diet and DASH (Dietary Approaches to Stop Hypertension) shown to have particular benefit. Regular physical activity, at a minimum of 150 minutes per week of moderate-intensity exercise, improves insulin sensitivity, aids weight management, and provides independent cardiovascular benefits.

Metformin, a biguanide, is the first-line pharmacologic agent for most patients with type 2 diabetes unless contraindicated. Its primary mechanism of action involves decreasing hepatic glucose output—specifically reducing gluconeogenesis—while also improving peripheral insulin sensitivity. Metformin is typically initiated at 500 mg daily and gradually titrated up to a maximum of 2000 mg per day, divided into two doses. Among its key advantages are weight neutrality (it does not cause weight gain and may promote modest weight loss), the absence of hypoglycemia when used as monotherapy (since it does not stimulate insulin secretion), low cost, and evidence of cardiovascular benefit.

The side effect profile of metformin is manageable but deserves attention. Gastrointestinal effects, including nausea, diarrhea, and abdominal discomfort, are the most common adverse effects and can be minimized by starting at a low dose, titrating slowly, and using the extended-release formulation. Long-term metformin use can lead to vitamin B12 deficiency, necessitating periodic monitoring of B12 levels, particularly in patients with symptoms of peripheral neuropathy. Lactic acidosis is an exceedingly rare but potentially fatal complication that is more likely to occur in the setting of severe renal or hepatic disease. Metformin is contraindicated when the estimated glomerular filtration rate (eGFR) falls below 30 mL/min/1.73m², and caution is advised when eGFR is between 30 and 45. Additionally, metformin should be held before procedures involving iodinated contrast dye due to the risk of acute kidney injury potentiating lactic acidosis.

<image>Panel A: Lifestyle modification recommendations showing 5-7% weight loss target, reduced calorie diet (Mediterranean or DASH), 150 minutes per week of moderate intensity exercise, and diabetes prevention data (58% risk reduction with lifestyle changes). Panel B: Metformin mechanism as biguanide decreasing hepatic glucose output and improving insulin sensitivity, first-line for most patients, with dosing starting at 500 mg and titrating to 2000 mg per day. Panel C: Metformin benefits showing weight neutrality, no hypoglycemia, low cost, and cardiovascular benefit as key advantages over other agents. Panel D: Metformin side effects and contraindications showing GI symptoms (nausea, diarrhea managed by slow titration and extended-release), vitamin B12 deficiency (monitor periodically), rare lactic acidosis, and contraindication at eGFR less than 30 mL/min with caution at 30-45 and holding before contrast procedures.</image>

IV. Type 2 Diabetes - Additional Oral Agents

When metformin alone is insufficient to achieve glycemic targets, a range of additional oral agents can be added as second- or third-line therapy. Each class operates through a distinct mechanism of action, and selection among them is guided by efficacy, side effect profile, effects on weight, hypoglycemia risk, cardiovascular and renal benefits, and cost considerations.

Sulfonylureas have been a mainstay of type 2 diabetes treatment for decades. They act by increasing insulin secretion from pancreatic beta cells through closure of ATP-sensitive potassium channels, which depolarizes the cell membrane and triggers insulin release. Commonly used second-generation sulfonylureas include glipizide, glyburide, and glimepiride, with second-generation agents preferred over first-generation drugs due to their more predictable pharmacokinetics. Sulfonylureas are effective at lowering HbA1c and are among the least expensive diabetes medications. However, their principal disadvantages are a significant risk of hypoglycemia—particularly with glyburide and in patients with renal impairment—and a tendency to promote weight gain.

SGLT2 (sodium-glucose cotransporter 2) inhibitors represent a newer class that has rapidly gained prominence due to their unique mechanism and broad cardiorenal benefits. These agents, including empagliflozin, dapagliflozin, and canagliflozin, work by blocking glucose reabsorption in the proximal tubule of the kidney, thereby promoting urinary glucose excretion. Beyond glucose lowering, SGLT2 inhibitors consistently promote weight loss and modest blood pressure reduction. Their most significant clinical advantage lies in proven cardiovascular and renal protection: large outcome trials have demonstrated reductions in major adverse cardiovascular events, hospitalization for heart failure, and progression of chronic kidney disease. Side effects include an increased risk of urinary tract infections, genital mycotic infections (particularly vulvovaginal candidiasis), and a rare but notable risk of euglycemic diabetic ketoacidosis.

DPP-4 (dipeptidyl peptidase-4) inhibitors, including sitagliptin, linagliptin, and saxagliptin, act by preventing the enzymatic degradation of the incretin hormone GLP-1 (glucagon-like peptide-1), thereby prolonging its glucose-lowering effects. This mechanism enhances glucose-dependent insulin secretion and suppresses glucagon release. DPP-4 inhibitors are weight neutral and carry no intrinsic risk of hypoglycemia, making them well tolerated. They are generally easy to use as oral once-daily medications. However, their primary limitation is modest efficacy compared to other classes, with HbA1c reductions typically in the range of 0.5 to 0.8%.

Thiazolidinediones (TZDs), represented primarily by pioglitazone and rosiglitazone, are agonists of the nuclear receptor PPARgamma (peroxisome proliferator-activated receptor gamma) and act by increasing insulin sensitivity in adipose tissue, muscle, and liver. TZDs produce durable glucose-lowering effects that may persist longer than many other oral agents, and pioglitazone has shown benefit in reducing non-alcoholic fatty liver disease (NAFLD). However, their use is limited by important adverse effects, including fluid retention, increased risk of heart failure exacerbation, increased fracture risk (particularly in postmenopausal women), and weight gain. Heart failure is a contraindication to TZD use.

Alpha-glucosidase inhibitors, such as acarbose and miglitol, delay the digestion and absorption of complex carbohydrates in the small intestine by inhibiting the alpha-glucosidase enzymes on the brush border. Their primary role is in targeting postprandial hyperglycemia. While they do not cause hypoglycemia when used as monotherapy and are weight neutral, their use is limited by frequent gastrointestinal side effects, particularly flatulence and diarrhea, which reduce patient adherence.

<image>Panel A: Sulfonylureas showing mechanism (increased insulin secretion by closing K-ATP channels), examples (glipizide, glyburide, glimepiride), benefits (effective, low cost), and risks (hypoglycemia, weight gain). Panel B: SGLT2 inhibitors showing mechanism (blocking renal glucose reabsorption), examples (empagliflozin, dapagliflozin, canagliflozin), benefits (weight loss, blood pressure reduction, cardiovascular and renal protection), and side effects (UTI, genital mycotic infections, euglycemic DKA). Panel C: DPP-4 inhibitors showing mechanism (preventing incretin GLP-1 degradation), examples (sitagliptin, linagliptin, saxagliptin), benefits (weight neutral, no hypoglycemia), and limitation of modest efficacy. Panel D: Thiazolidinediones and alpha-glucosidase inhibitors showing TZDs (pioglitazone as PPARgamma agonist improving insulin sensitivity with risks of fluid retention, heart failure, fractures) and alpha-glucosidase inhibitors (acarbose delaying carbohydrate absorption for postprandial control with GI side effects).</image>

V. Type 2 Diabetes - Injectable Agents

When oral agents alone fail to achieve glycemic targets, injectable therapies provide powerful additional options. GLP-1 receptor agonists have emerged as preferred agents in many clinical scenarios due to their glucose-lowering efficacy, weight loss benefits, and cardiovascular protection. Insulin therapy remains essential for patients with advanced beta cell failure or markedly elevated glucose levels.

GLP-1 (glucagon-like peptide-1) receptor agonists are incretin mimetics that activate the GLP-1 receptor to produce multiple beneficial effects. They increase glucose-dependent insulin secretion (meaning they stimulate insulin release only when glucose is elevated, minimizing hypoglycemia risk), suppress inappropriately elevated glucagon secretion, slow gastric emptying, and promote satiety. Available agents include semaglutide, dulaglutide, liraglutide, and exenatide, with varying administration schedules—some given daily and others weekly via subcutaneous injection. Oral semaglutide is also available, offering an oral route of administration for this class. The benefits of GLP-1 receptor agonists are substantial: they produce significant weight loss (often 3 to 7 kg or more), have proven cardiovascular protection (demonstrated for liraglutide, semaglutide, and dulaglutide), and carry a low risk of hypoglycemia. Side effects are predominantly gastrointestinal, including nausea and vomiting that typically diminish with continued use. Rare concerns include pancreatitis and a theoretical risk of medullary thyroid carcinoma (MTC), based on preclinical findings in rodents.

The dual GIP/GLP-1 receptor agonist tirzepatide represents the newest advance in incretin-based therapy. By simultaneously activating both the glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptors, tirzepatide achieves greater weight loss and glucose lowering than agents targeting GLP-1 alone. This dual mechanism appears to provide synergistic metabolic benefits that have set new benchmarks for HbA1c reduction and weight loss in clinical trials.

Insulin therapy becomes necessary in type 2 diabetes under several clinical circumstances. Patients presenting with an HbA1c greater than 10% may benefit from early insulin initiation to overcome significant glucose toxicity. Symptomatic hyperglycemia with weight loss and polyuria indicates substantial insulin deficiency requiring replacement. Progressive beta cell decline means that many patients will eventually require insulin despite maximal oral and injectable non-insulin therapy. Additionally, pregnancy in women with type 2 diabetes requires insulin, as most oral agents are not approved for use in pregnancy.

When insulin is initiated in type 2 diabetes, basal insulin is typically the first step. The starting dose is generally 10 units or 0.1 to 0.2 units per kilogram per day, administered at bedtime or in the morning. The dose is titrated upward by 2 to 4 units every 3 to 7 days, guided by fasting glucose measurements with a target of 80 to 130 mg/dL. If basal insulin alone is insufficient to achieve glycemic goals (as indicated by persistent postprandial hyperglycemia despite fasting glucose at target), bolus insulin can be added, beginning with a single dose at the largest meal.

<image>Panel A: GLP-1 receptor agonists showing incretin mimetic mechanism (increased glucose-dependent insulin, decreased glucagon), examples (semaglutide, dulaglutide, liraglutide), significant weight loss and cardiovascular protection benefits, with nausea and rare pancreatitis as side effects. Panel B: Dual GIP/GLP-1 agonist tirzepatide showing dual receptor activation mechanism, greater weight loss and glucose lowering compared to single incretin agents, with weekly subcutaneous and oral semaglutide administration options. Panel C: Insulin indications in type 2 diabetes showing HbA1c greater than 10%, symptomatic hyperglycemia (weight loss, polyuria), failure of oral agents from progressive beta cell decline, and pregnancy requiring insulin. Panel D: Basal insulin initiation in T2DM showing starting dose of 10 units or 0.1-0.2 units/kg, titration by 2-4 units every 3-7 days targeting fasting glucose 80-130 mg/dL, with option to add bolus insulin at the largest meal if basal alone is insufficient.</image>

VI. Treatment Algorithm for Type 2 Diabetes

Modern guidelines provide a structured, comorbidity-driven algorithm for selecting and sequencing therapies in type 2 diabetes. This approach recognizes that glycemic control is only one dimension of diabetes management, and that the presence of atherosclerotic cardiovascular disease, heart failure, or chronic kidney disease should drive agent selection toward medications with proven organ-protective benefits.

The first-line treatment for virtually all patients with newly diagnosed type 2 diabetes combines lifestyle modifications with metformin. However, contemporary guidelines emphasize that if a patient has established atherosclerotic cardiovascular disease (ASCVD), chronic kidney disease (CKD), or heart failure (HF) at the time of diagnosis, an SGLT2 inhibitor or GLP-1 receptor agonist with proven benefit for that condition should be considered as part of the initial regimen, independent of HbA1c level and potentially even before or alongside metformin.

When a second agent is needed to achieve glycemic targets, selection is guided primarily by the patient's comorbidity profile. For patients with established ASCVD, a GLP-1 receptor agonist or SGLT2 inhibitor with demonstrated cardiovascular benefit is preferred. Heart failure, particularly heart failure with reduced ejection fraction, favors SGLT2 inhibitors given their strong evidence for reducing heart failure hospitalizations. CKD favors SGLT2 inhibitors for their renal protective effects, with GLP-1 receptor agonists as an alternative. When the primary concern is avoiding hypoglycemia, GLP-1 receptor agonists, SGLT2 inhibitors, DPP-4 inhibitors, and TZDs are all appropriate options. When weight loss is a priority, GLP-1 receptor agonists and SGLT2 inhibitors are preferred. Cost constraints may lead to selection of sulfonylureas or TZDs, which remain among the least expensive options.

Intensification occurs when patients fail to reach glycemic goals on dual therapy. A third agent from a complementary class can be added, or insulin can be initiated if the HbA1c remains significantly above target. Patients with very high HbA1c (greater than 10%) or those who are symptomatic with polyuria, polydipsia, and weight loss may need insulin early in their treatment course. In symptomatic patients, insulin may be combined with other agents to address both the immediate need for glucose control and the underlying pathophysiology.

For patients who require injectable therapy, a stepwise progression is typically followed. Basal insulin alone is initiated first, as described previously. If basal insulin is insufficient, bolus insulin is added at the largest meal (basal-plus regimen), then expanded to two or three bolus doses as needed (basal-bolus regimen). An effective alternative to the basal-bolus approach is the combination of a GLP-1 receptor agonist with basal insulin, which provides complementary mechanisms (the GLP-1 agonist addresses postprandial glucose and promotes weight loss while basal insulin controls fasting glucose) and is often better tolerated than full basal-bolus regimens.

<image>Panel A: First-line therapy showing lifestyle modifications plus metformin at diagnosis, with consideration of SGLT2 inhibitor or GLP-1 receptor agonist if atherosclerotic CVD, CKD, or heart failure is present at diagnosis. Panel B: Second agent selection by comorbidity showing ASCVD (GLP-1 RA or SGLT2i with proven CV benefit), heart failure (SGLT2i), CKD (SGLT2i or GLP-1 RA), need to avoid hypoglycemia (GLP-1 RA, SGLT2i, DPP-4i, TZD), weight loss need (GLP-1 RA, SGLT2i), and cost concerns (sulfonylurea, TZD). Panel C: Intensification approach showing addition of third agent or insulin if not at goal on two agents, early insulin consideration if HbA1c greater than 10%, and insulin with other agents if symptomatic. Panel D: Injectable progression steps showing basal insulin alone first, then basal plus one bolus at largest meal, then basal plus 2-3 bolus doses, with GLP-1 RA plus basal insulin as an effective alternative combination.</image>

VII. Management of DKA

Diabetic ketoacidosis (DKA) is a life-threatening metabolic emergency characterized by hyperglycemia, ketosis, and metabolic acidosis. It occurs most commonly in type 1 diabetes but can also occur in type 2 diabetes under severe physiologic stress. Successful management requires a systematic approach to fluid resuscitation, insulin therapy, electrolyte replacement, and identification of the precipitating cause.

Initial assessment follows the standard approach to any critically ill patient, beginning with evaluation of the airway, breathing, and circulation (ABCs). Essential laboratory studies include a basic metabolic panel, serum glucose, serum and urine ketones, arterial blood gas, and complete blood count. Assessment of the patient's volume status is critical, as DKA typically presents with a fluid deficit of 4 to 6 liters due to osmotic diuresis and vomiting. Identifying and treating the precipitating factor is equally important—common triggers include infection (the most common cause), non-compliance with insulin therapy, new-onset diabetes, and other acute medical or surgical conditions.

Fluid resuscitation is the first priority and should be initiated before insulin in most cases. The initial protocol calls for 0.9% normal saline at 15 to 20 mL/kg/hr during the first 1 to 2 hours (typically 1 to 1.5 liters in the first hour for an average-sized adult). Subsequent fluid rates are adjusted to 250 to 500 mL/hr based on hemodynamic status, urine output, and electrolyte levels. When the serum glucose falls below 200 to 250 mg/dL, intravenous fluids should be changed to contain 5% dextrose (D5) to prevent hypoglycemia while continuing insulin to clear ketones. The transition from normal saline to 0.45% (half-normal) saline is guided by the corrected serum sodium: if the corrected sodium is normal or high, switching to half-normal saline is appropriate.

Insulin therapy is essential to suppress ketogenesis and correct the metabolic acidosis. An optional initial intravenous bolus of 0.1 units/kg may be administered, followed by a continuous intravenous infusion at 0.1 units/kg/hr. The target rate of glucose decline is 50 to 75 mg/dL per hour; if the glucose is not falling at this rate, the infusion should be increased. When glucose reaches 200 to 250 mg/dL, dextrose is added to the intravenous fluids, but insulin should not be stopped—rather, the rate may be reduced. The critical principle is that the insulin infusion must be continued until the anion gap has closed, as this indicates resolution of ketoacidosis, regardless of whether the glucose has already normalized.

Potassium management is among the most dangerous aspects of DKA treatment and requires meticulous attention. Although patients with DKA are invariably total-body potassium depleted, the serum potassium may be normal or even elevated at presentation due to extracellular shifts driven by acidosis and insulin deficiency. Insulin therapy drives potassium intracellularly, and hypokalemia can rapidly develop. If the initial serum potassium is less than 3.3 mEq/L, insulin must be held and potassium replaced aggressively at 20 to 40 mEq/hr until levels exceed 3.3 mEq/L, as administering insulin in the setting of severe hypokalemia risks life-threatening cardiac arrhythmias. When potassium is between 3.3 and 5.3 mEq/L, 20 to 30 mEq of potassium should be added to each liter of intravenous fluid. When potassium exceeds 5.3 mEq/L, potassium supplementation should be withheld and levels rechecked every 2 hours.

Bicarbonate administration is reserved for severe acidosis with a pH less than 6.9. The protocol calls for 100 mEq of sodium bicarbonate in 400 mL of water administered over 2 hours. Routine bicarbonate use is not recommended when the pH is 6.9 or higher, as insulin therapy and fluid resuscitation will correct the acidosis as ketone production ceases. Resolution of DKA is defined by glucose less than 200 to 250 mg/dL, closure of the anion gap to less than 12, pH greater than 7.3, and serum bicarbonate of 18 mEq/L or greater. Transition from intravenous to subcutaneous insulin should include an overlap period of 1 to 2 hours, during which both the insulin drip and the first subcutaneous dose are given simultaneously, to prevent rebound hyperglycemia and ketosis.

<image>Panel A: Initial assessment and fluid resuscitation showing ABCs evaluation, labs (BMP, glucose, ketones, ABG), 4-6 liter typical fluid deficit, starting with 0.9% normal saline at 15-20 mL/kg/hr for first 1-2 hours, then 250-500 mL/hr, switching to D5 when glucose less than 200-250 mg/dL. Panel B: Insulin therapy protocol showing optional 0.1 units/kg IV bolus, continuous infusion at 0.1 units/kg/hr targeting glucose decrease of 50-75 mg/dL per hour, adding dextrose when glucose below 200-250, and continuing insulin until anion gap closes. Panel C: Potassium management algorithm showing hold insulin and give 20-40 mEq/hr if potassium less than 3.3, add 20-30 mEq to each liter if 3.3-5.3, withhold potassium and check every 2 hours if greater than 5.3, with warning that insulin drives potassium intracellularly. Panel D: Resolution criteria and transition showing glucose less than 200-250, anion gap less than 12, pH greater than 7.3, bicarbonate 18 or greater, with overlap of IV and subcutaneous insulin by 1-2 hours before discontinuing the drip, and bicarbonate use only if pH less than 6.9.</image>

VIII. Management of HHS

Hyperosmolar hyperglycemic state (HHS) is a severe metabolic emergency that occurs predominantly in type 2 diabetes, characterized by profound dehydration, extreme hyperglycemia (often exceeding 600 mg/dL), and hyperosmolality, but without significant ketoacidosis. The hallmark of HHS management is aggressive fluid replacement, which is even more critical than in DKA given the typically larger volume deficits. Mortality rates for HHS remain higher than for DKA, largely due to the older age and comorbidity burden of affected patients.

Fluid resuscitation is the single most critical intervention in HHS. The volume deficit is often staggering, ranging from 8 to 12 liters, reflecting prolonged osmotic diuresis in patients who may have had inadequate oral intake for days. Initial fluid administration consists of 0.9% normal saline at 15 to 20 mL/kg/hr. Subsequent fluid choice and rate are guided by hemodynamic status and serum sodium levels, with the corrected sodium helping to determine whether to continue isotonic saline or transition to 0.45% saline. The goal is to replace approximately 50% of the estimated fluid deficit within the first 12 hours, with the remainder replaced over the following 24 to 36 hours. Importantly, fluid resuscitation alone often produces a significant reduction in serum glucose, even before insulin is administered, through dilution and improved renal perfusion with resultant glycosuria.

Insulin therapy in HHS is initiated after the initial fluid bolus has been administered and volume resuscitation is underway. The infusion rate is typically 0.1 units/kg/hr, similar to or slightly lower than DKA protocols. The target glucose decline is 50 to 75 mg/dL per hour. Caution must be exercised to avoid too-rapid a drop in serum glucose, as the resulting rapid shift in serum osmolality can precipitate cerebral edema—a rare but devastating complication. Because fluids alone often lower glucose substantially in HHS, insulin requirements may be lower than initially expected.

Electrolyte management in HHS follows similar principles to DKA. Potassium depletion is universal and requires the same monitoring and replacement algorithm: holding insulin and aggressively replacing potassium if levels fall below 3.3 mEq/L, adding potassium to intravenous fluids for levels between 3.3 and 5.3 mEq/L, and withholding supplementation above 5.3 mEq/L. Sodium must be carefully monitored, with corrected sodium values guiding fluid composition choices. Phosphate replacement is indicated if levels fall below 1 mg/dL, though routine replacement is not necessary.

Close monitoring is essential throughout HHS management. Serum glucose should be measured hourly to ensure an appropriate rate of decline and to guide insulin adjustments. Electrolytes and serum osmolality should be assessed every 2 to 4 hours. Mental status must be evaluated frequently, as altered consciousness is a hallmark of HHS and should improve with treatment—failure to improve or deterioration should prompt consideration of cerebral edema or other comorbid conditions. The overarching principle is gradual correction: overly rapid correction of hyperglycemia and hyperosmolality risks precipitating cerebral edema, which can be fatal.

<image>Panel A: Fluid resuscitation as top priority showing often 8-12 liter deficit, starting with 0.9% normal saline at 15-20 mL/kg/hr, subsequent fluid based on hemodynamics and sodium, with goal to replace 50% of deficit in first 12 hours. Panel B: Insulin approach showing initiation after initial fluid bolus at 0.1 units/kg/hr (or lower), targeting glucose decrease of 50-75 mg/dL per hour, with caution to avoid too-rapid glucose drop, and note that fluids alone often significantly lower glucose. Panel C: Electrolyte management showing potassium replacement same as DKA protocol (monitoring shifts), sodium monitoring with corrected sodium guiding fluid choice, and phosphate replacement if less than 1 mg/dL. Panel D: Monitoring parameters and goals showing hourly glucose, electrolytes and osmolality every 2-4 hours, frequent mental status assessment, with goal of gradual correction to avoid cerebral edema as a dangerous complication.</image>

IX. Chronic Complications - Screening and Management

Diabetes mellitus is a systemic disease whose chronic complications affect virtually every organ system. The microvascular complications—retinopathy, nephropathy, and neuropathy—are directly related to the duration and severity of hyperglycemia, while macrovascular disease (cardiovascular disease) is driven by the complex metabolic milieu of diabetes including dyslipidemia, hypertension, and inflammation. Systematic screening and early intervention are essential to prevent or delay the progression of these complications.

Diabetic retinopathy is the leading cause of blindness in working-age adults and requires regular screening by dilated fundoscopic examination. For patients with type 2 diabetes, screening should begin at the time of diagnosis (since many have had undiagnosed hyperglycemia for years), while for type 1 diabetes, screening begins 5 years after diagnosis. Subsequent examinations are performed annually, though the interval may be extended in patients with consistently normal findings. Fundoscopic findings range from early nonproliferative changes such as microaneurysms, dot-blot hemorrhages, and hard exudates, to the more advanced and vision-threatening proliferative retinopathy characterized by neovascularization. Treatment of advanced retinopathy includes laser photocoagulation and intravitreal anti-VEGF (vascular endothelial growth factor) injections. Prevention centers on maintaining good glycemic control and blood pressure control, both of which have been shown to slow retinopathy progression.

Diabetic nephropathy is the most common cause of end-stage renal disease in developed countries. Screening consists of an annual urine albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR). Diabetic nephropathy is defined by a UACR of 30 mg/g or greater or an eGFR less than 60 mL/min/1.73m². The mainstay of treatment includes angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB), which reduce intraglomerular pressure and slow the progression of albuminuria. SGLT2 inhibitors have demonstrated remarkable renoprotective effects, reducing the risk of progression to end-stage kidney disease. Finerenone, a non-steroidal mineralocorticoid receptor antagonist, has shown additional benefit in reducing kidney and cardiovascular outcomes in patients with type 2 diabetes and CKD. Blood pressure control to a target of less than 130/80 mmHg is an essential adjunct to pharmacotherapy.

Diabetic neuropathy takes multiple forms. Distal symmetric polyneuropathy is the most common pattern, presenting with a characteristic stocking-glove distribution of pain, burning, tingling, and numbness that begins in the feet and progresses proximally. Autonomic neuropathy can affect multiple organ systems, manifesting as gastroparesis (delayed gastric emptying), cardiovascular autonomic neuropathy with resting tachycardia and orthostatic hypotension, and erectile dysfunction. Screening for distal neuropathy should include an annual monofilament examination to assess protective sensation in the feet. Treatment includes pain management with agents such as pregabalin, duloxetine, or gabapentin; comprehensive foot care to prevent ulceration and amputation; and glycemic control to slow progression.

Cardiovascular disease represents the leading cause of morbidity and mortality in patients with diabetes, with a 2 to 4 times increased risk compared to the general population. Risk factor assessment should be performed regularly, with consideration of stress testing in appropriate patients. Treatment includes statin therapy for cholesterol management (recommended for virtually all adults with diabetes over age 40), aspirin for secondary prevention in those with established cardiovascular disease, and blood pressure control. The SGLT2 inhibitors and GLP-1 receptor agonists with proven cardiovascular benefit should be prioritized in patients with established ASCVD or at high cardiovascular risk. Comprehensive foot care rounds out the complication prevention strategy, including daily patient self-inspection of the feet, annual comprehensive foot examinations with monofilament testing and pedal pulse assessment, proper-fitting footwear, avoidance of walking barefoot, and careful attention to nail care and prevention of cuts and burns.

<image>Panel A: Retinopathy screening showing dilated eye exam at diagnosis for type 2 (5 years after for type 1) then annually, findings of microaneurysms, hemorrhages, exudates, and neovascularization, treatment with laser photocoagulation and anti-VEGF injections, and prevention through glycemic and blood pressure control. Panel B: Nephropathy screening showing annual urine albumin-to-creatinine ratio (UACR) and eGFR, definition as UACR 30 mg/g or greater or eGFR less than 60, treatment with ACE inhibitor or ARB, SGLT2 inhibitor, and finerenone, targeting blood pressure less than 130/80. Panel C: Neuropathy screening showing annual monofilament exam, distal symmetric polyneuropathy (stocking-glove pain and numbness), autonomic neuropathy (gastroparesis, orthostatic hypotension, erectile dysfunction), and treatment with pain management, foot care, and glycemic control. Panel D: Cardiovascular disease and foot care showing 2-4 times increased CVD risk managed with statins, aspirin for secondary prevention, BP control, and SGLT2i or GLP-1 RA with CV benefit, alongside foot care recommendations (daily inspection, proper footwear, annual comprehensive exam).</image>

X. Hypoglycemia

Hypoglycemia is the most common acute complication of diabetes treatment and represents the principal barrier to achieving tight glycemic control. It is most frequently associated with insulin therapy and sulfonylureas, though it can occur with any glucose-lowering regimen under certain circumstances. Recognizing, treating, and preventing hypoglycemia is a critical component of diabetes education for patients, families, and healthcare providers.

Hypoglycemia is classified into three levels of severity. Level 1 hypoglycemia is defined as a glucose level less than 70 mg/dL, which serves as an alert value prompting the patient to take corrective action. Level 2 hypoglycemia, defined as glucose less than 54 mg/dL, is considered clinically significant and requires immediate treatment, as cognitive impairment becomes more likely at this threshold. Level 3 hypoglycemia is severe, characterized by altered mental status or physical functioning that requires the assistance of another person for treatment.

The symptoms of hypoglycemia are divided into two categories based on their underlying mechanism. Autonomic (adrenergic) symptoms result from the counterregulatory hormone response and include sweating, tremor, palpitations, hunger, and anxiety. These symptoms typically appear first and serve as early warning signals. Neuroglycopenic symptoms reflect inadequate glucose delivery to the brain and include confusion, difficulty concentrating, slurred speech, and, in severe cases, seizures and coma. A particularly dangerous phenomenon is hypoglycemia unawareness, in which recurrent episodes of hypoglycemia blunt the counterregulatory hormone response, leading to loss of the autonomic warning symptoms. Patients with hypoglycemia unawareness are at substantially increased risk for severe hypoglycemic episodes because they do not perceive the early warning signs that would otherwise prompt corrective action.

Multiple factors can precipitate hypoglycemia in patients with diabetes. Excessive insulin dosing—whether from a calculation error, incorrect injection technique, or failure to account for reduced requirements—is the most common cause. Missed or delayed meals create a mismatch between insulin action and glucose availability. Increased physical activity lowers glucose levels and may cause delayed hypoglycemia if carbohydrate intake or insulin dose is not adjusted. Alcohol inhibits hepatic gluconeogenesis, increasing the risk of hypoglycemia, particularly overnight or in the fasting state. Sulfonylureas are particularly associated with hypoglycemia, especially glyburide and especially in patients with renal impairment, which decreases drug and active metabolite clearance. Renal failure of any cause decreases insulin clearance, prolonging its glucose-lowering effect.

Treatment of hypoglycemia depends on severity. For mild to moderate episodes in conscious patients, the "Rule of 15" is the standard approach: administer 15 to 20 grams of fast-acting carbohydrates (glucose tablets, fruit juice, or regular soda), wait 15 minutes, and recheck the glucose level. If glucose remains below 70 mg/dL, the treatment is repeated. For severe hypoglycemia in an unconscious or uncooperative patient who cannot safely take oral carbohydrates, glucagon is the treatment of choice in the outpatient setting. Glucagon is available in an injectable form (1 mg intramuscularly or subcutaneously) and a nasal form (3 mg intranasal), the latter being particularly easy for lay caregivers to administer. In the hospital setting, intravenous dextrose (typically 25 to 50 mL of D50W) provides the most rapid correction. Patient education is essential: all patients on insulin or sulfonylureas should carry fast-acting carbohydrates, and family members and caregivers should be trained in glucagon administration.

Prevention of hypoglycemia requires a multifaceted strategy. Self-monitoring of blood glucose (SMBG) and continuous glucose monitoring (CGM) allow patients to identify glucose patterns and detect impending lows. Carbohydrate counting enables precise matching of insulin doses to meal content. Insulin doses should be reduced and/or carbohydrate intake increased before and during physical activity. In patients at high risk for hypoglycemia, avoiding sulfonylureas in favor of agents that do not cause hypoglycemia (such as GLP-1 receptor agonists or SGLT2 inhibitors) is prudent. CGM with low glucose alarms provides an early warning system that is particularly valuable for patients with hypoglycemia unawareness, allowing corrective action before glucose reaches dangerous levels.

<image>Panel A: Hypoglycemia classification showing level 1 (less than 70 mg/dL, alert value), level 2 (less than 54 mg/dL, clinically significant), and level 3 (severe, requires assistance), with common causes including insulin dose errors, missed meals, increased exercise, alcohol, and sulfonylureas. Panel B: Symptom categories showing autonomic symptoms (sweating, tremor, palpitations, hunger, anxiety) and neuroglycopenic symptoms (confusion, difficulty concentrating, slurred speech, seizures, coma), with hypoglycemia unawareness as loss of warning symptoms increasing severe episode risk. Panel C: Rule of 15 treatment showing 15 grams of fast-acting carbohydrates (glucose tablets, juice, regular soda), wait 15 minutes, recheck glucose, and repeat if still low, for mild to moderate hypoglycemia in conscious patients. Panel D: Glucagon administration for severe hypoglycemia showing injectable form (1 mg IM or SQ), nasal form (3 mg intranasal), indication when patient unable to take oral carbohydrates, and prevention strategies including SMBG/CGM monitoring, carb counting, exercise adjustment, and CGM alarms for early warning.</image>

Summary

• Glycemic targets: HbA1c <7% for most; individualize based on patient factors
• Type 1 DM: Requires insulin (basal-bolus or pump); CGM improves outcomes
• Type 2 DM: Lifestyle + metformin first-line; add agents based on comorbidities
• Cardiorenal benefit: SGLT2i and GLP-1 RA have proven CV and renal benefits
• DKA treatment: Fluids, insulin, potassium replacement; close monitoring
• HHS treatment: Aggressive fluid resuscitation; slower insulin correction
• Complications: Screen for retinopathy, nephropathy, neuropathy, CVD
• Hypoglycemia: 15-15 rule for mild; glucagon for severe

Key Terms

This content is subject to the MIT License. © 2024–2026 Hibbert School of Medicine.

Read this lecture as Markdown