Residency · Residency · Internal Medicine
Inpatient Glycemic Management and Insulin Dosing
Overview
Hyperglycemia in hospitalized patients, whether they have known diabetes or not, is associated with increased morbidity and mortality. Basal-bolus insulin is the standard of care for non-critically ill hospitalized patients, and sliding scale insulin alone is inadequate. Glycemic targets differ between ICU and non-ICU settings, and key challenges include steroid-induced hyperglycemia, insulin pump management, transition from IV to subcutaneous insulin, and hypoglycemia prevention.
Glycemic Targets
| Setting | Glucose Target | Key Notes |
|---|---|---|
| Non-critically ill (ward) | Pre-meal 100-180 mg/dL | Avoid <70 and >250 mg/dL |
| Terminally ill / high hypoglycemia risk | <200 mg/dL | More liberal targets |
| Critically ill (ICU) | 140-180 mg/dL | NICE-SUGAR: tight control increased mortality |
| Perioperative | <180 mg/dL | Reduces surgical site infection risk |
Non-Critically Ill (Ward Patients)
The general target for pre-meal glucose is 100-180 mg/dL. Glucose below 70 mg/dL (hypoglycemia) and above 250 mg/dL (severe hyperglycemia) should be avoided. More liberal targets (below 200 mg/dL) are appropriate for terminally ill patients or those at high risk for hypoglycemia.
Critically Ill (ICU Patients)
The target in the ICU is 140-180 mg/dL. The NICE-SUGAR trial demonstrated that tight glucose control (81-108 mg/dL) increased mortality compared to conventional control (below 180 mg/dL). Continuous IV insulin infusion is the standard approach in the ICU.
<image>Comparison of inpatient glycemic targets for ICU versus non-ICU patients with supporting trial evidence including NICE-SUGAR results</image>
Basal-Bolus Insulin Regimen
Principles
Basal insulin (glargine, detemir, or NPH) provides background insulin to control fasting and between-meal glucose. Bolus (prandial) insulin (rapid-acting: lispro, aspart, glulisine) covers mealtime glucose excursions. Correction insulin is supplemental rapid-acting insulin added to prandial doses to correct pre-meal hyperglycemia.
Initial Dosing Calculation
The total daily dose (TDD) is estimated first. For type 2 diabetes patients not on insulin at home, 0.3-0.5 units/kg/day is used. For those on insulin at home, the home dose serves as a starting point with potential adjustments. Type 1 diabetes patients use their home TDD, and basal insulin should never be held. For elderly patients, those with CKD, hepatic disease, or malnutrition, a lower starting dose of 0.2-0.3 units/kg/day helps avoid hypoglycemia.
The TDD is divided with 50% as basal insulin (once or twice daily) and 50% as bolus insulin (divided equally among three meals). The correction factor (sensitivity factor) uses the 1800 rule: 1800 divided by TDD equals the expected glucose drop per unit of rapid-acting insulin, and correction insulin is added to prandial doses based on pre-meal glucose.
Adjusting the Regimen
Blood glucose logs should be reviewed daily. Consistently high fasting glucose calls for increasing basal by 10-20%. High pre-dinner glucose warrants increasing the lunch bolus. Significant hypoglycemia requires reducing TDD by 20-40%. When a patient is NPO, bolus insulin is held while basal continues (possibly reduced by 20-50% depending on the type).
Special Scenarios
Steroid-Induced Hyperglycemia
Steroids cause insulin resistance predominantly in the afternoon and evening when dosed in the morning. For prednisone, NPH insulin given at the time of the steroid dose works well due to pharmacokinetic matching, starting at 0.1 units/kg per 10 mg of prednisone. Dexamethasone is longer-acting and may require a basal insulin increase or NPH twice daily. High-dose pulse steroids (methylprednisolone 1 g) should prompt anticipation of severe hyperglycemia with possible need for an insulin drip temporarily.
NPO Patients
Basal insulin should be continued (reduced by 20-50% for safety) while all prandial insulin is held. Glucose is monitored every 4-6 hours with correction insulin used only for significant hyperglycemia. In Type 1 diabetes, basal insulin must never be held entirely or DKA will develop.
Enteral Tube Feeding
For continuous feeds, basal insulin plus correction every 6 hours is appropriate. For bolus feeds, basal plus prandial insulin timed with feeds is used. If feeds are interrupted, there is high risk of hypoglycemia and insulin should be reduced or held accordingly.
Insulin Pump Patients
If the patient is alert and can manage the pump, it may be continued with physician oversight. If the patient is obtunded, going to surgery, or in the ICU, transition to an IV insulin drip is appropriate. Pump settings (basal rates, carb ratio, correction factor) should be documented on admission.
Transition from IV to Subcutaneous Insulin
The first dose of subcutaneous basal insulin should be given 2-4 hours before stopping the drip. The TDD is calculated from IV insulin by using 80% of the 24-hour IV insulin requirement, divided 50% basal and 50% bolus. Simply stopping the drip and starting subcutaneous insulin is never appropriate, as it results in hours of uncontrolled hyperglycemia.
<image>Basal-bolus insulin regimen diagram showing total daily dose calculation, 50/50 split between basal and bolus components, and correction factor application</image>
Continuous Glucose Monitoring (CGM) in the Hospital
CGM has an emerging role in inpatient settings, though the FDA has not approved most devices for inpatient use (with select models approved for specific settings). Potential advantages include reduced fingersticks, trend data, and hypoglycemia detection. Current limitations include accuracy concerns during critical illness (hypotension, edema, vasopressors) and medication interference (acetaminophen in older sensors). The COVID-19 pandemic accelerated adoption due to reduced nursing contact.
Hypoglycemia Management
Recognition and Risk Factors
Level 1 hypoglycemia is defined as blood glucose below 70 mg/dL, Level 2 (clinically significant) as below 54 mg/dL, and Level 3 as altered mental status with hypoglycemia. Risk factors include renal insufficiency, hepatic failure, reduced oral intake, missed meals, unadjusted insulin doses, and elderly age. Hypoglycemia in hospitalized patients is independently associated with increased mortality.
Treatment
For conscious patients, 15-20 g of fast-acting oral glucose is administered with a recheck in 15 minutes. For unconscious patients or those unable to swallow, D50 25 mL IV push is given, or glucagon 1 mg IM/SC if no IV access is available. The cause should be identified and addressed, with the insulin regimen adjusted accordingly.
<image>Flowchart for insulin dose adjustment in hospitalized patients based on blood glucose patterns including fasting hyperglycemia, pre-meal hyperglycemia, and hypoglycemia scenarios</image>
Non-Insulin Agents in the Hospital
| Agent Class | Inpatient Action | Reason |
|---|---|---|
| Metformin | Hold | AKI risk, contrast, hemodynamic instability |
| SGLT2 inhibitors | Hold | Euglycemic DKA, volume depletion, AKI |
| Sulfonylureas | Hold | Prolonged hypoglycemia, unpredictable intake |
| DPP-4 inhibitors | May continue | Low hypoglycemia risk; useful for mild hyperglycemia |
| GLP-1 receptor agonists | Hold | Nausea, reduced intake, delayed gastric emptying |
Most oral hypoglycemics should be held during hospitalization. Metformin is held if there is AKI risk, contrast exposure, or hemodynamic instability due to lactic acidosis risk. SGLT2 inhibitors are held in acute illness due to risks of euglycemic DKA, volume depletion, and AKI. Sulfonylureas are held due to prolonged hypoglycemia risk and unpredictable oral intake. DPP-4 inhibitors (such as sitagliptin) may be continued or used alone for mild hyperglycemia given their low hypoglycemia risk. GLP-1 receptor agonists are generally held in acute illness due to nausea, reduced intake, and delayed gastric emptying.
Clinical Pearls
Sliding scale insulin alone is never appropriate as the sole insulin regimen because it is reactive rather than proactive and leads to glycemic swings. The most common cause of inpatient hypoglycemia is insulin given without matching nutritional intake, so insulin should always be reassessed when diet orders change. Type 1 diabetes patients must always receive basal insulin, even when NPO, because without it they will develop DKA within hours. Hemoglobin A1c on admission helps distinguish new-onset diabetes from stress hyperglycemia, with A1c of 6.5% or higher suggesting pre-existing diabetes. "Stacking" correction insulin (giving additional doses before the previous dose has peaked) is a common cause of inpatient hypoglycemia. Perioperative glucose above 180 mg/dL is associated with increased surgical site infection risk.
References
- Umpierrez GE, et al. Randomized Study of Basal-Bolus Insulin Therapy in the Inpatient Management of Patients With Type 2 Diabetes (RABBIT 2 Trial). Diabetes Care. 2007;30:2181-2186.
- NICE-SUGAR Study Investigators. Intensive versus Conventional Glucose Control in Critically Ill Patients. N Engl J Med. 2009;360:1283-1297.
- American Diabetes Association. Standards of Care in Diabetes -- 2024: Diabetes Care in the Hospital. Diabetes Care. 2024;47(Suppl 1):S295-S306.
- Umpierrez GE, Pasquel FJ. Management of Inpatient Hyperglycemia and Diabetes in Older Adults. Diabetes Care. 2017;40:509-517.
- Galindo RJ, et al. Continuous Glucose Monitors for Inpatient Diabetes Management. Endocr Pract. 2020;26:1140-1149.
