Understanding type 1 diabetes

What type 1 diabetes is, why it happens, how it's diagnosed, what daily care looks like, and what it means for your family, in plain words.

6 min read · last reviewed October 3, 2026

A type 1 diabetes diagnosis can turn life upside down, for you and the people who love you. One day you're feeling unwell and can't work out why. The next, you're learning about insulin, carbs and blood sugar numbers. It's a lot.

Take a breath. People with type 1 diabetes go to school, work, play sports, travel, have families and live long, full lives. Insulin, glucose sensors and newer technology make that more possible than ever. This guide explains what's going on in your body, one step at a time.

What is type 1 diabetes?

Your pancreas, a small organ behind your stomach, contains clusters of cells called beta cells. These make insulin, a hormone that works like a key. Insulin unlocks your cells so sugar (glucose) from your food can get in and be used for energy.

In type 1 diabetes, your immune system, which normally fights germs, attacks and destroys the beta cells by mistake. This is called an autoimmune condition. Over time, the pancreas makes little or no insulin. Without insulin, sugar builds up in the blood, and your cells go hungry for fuel.

Because the body can't make enough insulin, everyone with type 1 diabetes needs to take insulin every day. It isn't optional, and it isn't a sign of anything you did wrong. It's simply replacing what your body can no longer make.

Why did this happen?

Nothing you did caused type 1 diabetes, and it couldn't have been prevented. It isn't caused by eating sugar, by weight or by lifestyle. Researchers believe it comes from a mix of genes and something in the environment, perhaps a virus, that triggers the immune system. It can run in families, but most people diagnosed don't have a close relative with it.

Type 1 diabetes makes up about 5 to 10% of all diabetes. It's often diagnosed in children and teens, but it can start at any age, and many people are diagnosed as adults. In adults, it's sometimes mistaken for type 2 diabetes at first.

How is it diagnosed?

Symptoms often come on over days to weeks. They can include:

• feeling very thirsty and peeing a lot
• losing weight without trying
• feeling very tired or weak
• blurry vision
• feeling sick, throwing up or stomach pain, which can be signs of DKA (see below)

Your team will check your blood sugar and A1C. To confirm it's type 1, they may test your blood for antibodies (signs the immune system is attacking the pancreas) and measure C-peptide, which shows how much insulin your body is still making.

Some people are diagnosed in hospital with diabetic ketoacidosis (DKA). This happens when there isn't enough insulin and the body burns fat for fuel, making acids called ketones. If that was your experience, know that DKA can usually be prevented from now on. See DKA: what to know.

Something you can do today: Ask your team to explain how they confirmed your diagnosis, and write down your results.

The "honeymoon" phase

After you start insulin, your remaining beta cells may get a rest and start working a bit better for a while. You might need less insulin, and your blood sugar might be easier to manage. This is called the honeymoon phase. It can last weeks, months or sometimes longer, but it does end. Your insulin needs will then go up. That's expected, not a setback.

What daily care looks like

Type 1 diabetes care is about matching insulin to what your body needs. You'll learn to:

• Take insulin, usually a long-acting (basal) insulin plus mealtime (bolus) insulin, or through an insulin pump. See Insulin and technology.
• Check your blood sugar, usually with a continuous glucose monitor (CGM), a small sensor that reads your sugar day and night. NICE in the UK recommends offering CGM to all adults with type 1 diabetes. Coverage in Canada and the U.S. depends on your province, state or insurance plan.
• Count carbohydrates, so you can match your mealtime insulin to what you eat.
• Prevent and treat lows, and keep glucagon on hand.
• Check ketones when you're sick or your blood sugar is high.

That sounds like a lot, and at first it is. With practice, most of it becomes routine. Your diabetes educator will teach you step by step.

What are the targets?

Your team will set targets with you. As a guide, many adults with type 1 diabetes aim for:

• an A1C of 7.0% or lower
• blood sugar of 4.0 to 7.0 mmol/L (about 70 to 126 mg/dL) before meals
• if you use a CGM, spending more than 70% of the day in range (3.9 to 10.0 mmol/L, or 70 to 180 mg/dL), with as little time low as possible

Safety from lows comes first. Your targets may be different, especially at first.

Looking ahead

Over many years, high blood sugar can affect the eyes, kidneys, nerves, heart and feet. Keeping blood sugar near target, plus regular checks, lowers these risks a lot. For adults with type 1 diabetes, eye and kidney checks usually start about 5 years after diagnosis, then continue every year.

Research is moving fast. Newer technology, such as automated insulin delivery, is making daily life easier. A medicine called teplizumab can delay type 1 diabetes in some people who are found early through antibody screening, and research into beta cell replacement continues.

For your family

Close relatives of people with type 1 diabetes have a higher chance of developing it. Ask your team whether antibody screening makes sense for your children, brothers or sisters. Family members can also learn how to treat lows and use glucagon.

Something you can do this week: Teach one family member or friend the signs of a low and how to treat it.

Questions to ask your care team

• How did you confirm that I have type 1 diabetes?
• What are my targets?
• Can I get a CGM? Is it covered?
• How do I count carbs?
• When should I check ketones?
• Should my family members be screened?

This article is general information, not medical advice. Talk with your health care team about your own situation. In an emergency, call 9-1-1 or your local emergency number.

In an emergency, call 9-1-1 or your local emergency number.

General information, not medical advice. It does not replace your own care team. If you think you or someone else is having a medical emergency, call 9-1-1 or your local emergency number. If you are in crisis or thinking about suicide, call or text 9-8-8 (Canada and the US).

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