Type 1 vs Type 2 Diabetes: A Side-by-Side Comparison
In type 1 diabetes the immune system destroys insulin-making cells, so insulin is needed every day. In type 2, the body does not use insulin well and may not make enough; it is far more common, at about 90 to 95 percent of cases. Only a clinician can tell which type you have.
| Type 1 | Type 2 | |
|---|---|---|
| What happens | The immune system destroys the insulin-making cells in the pancreas, so the body makes little or no insulin. | Cells do not use insulin well (insulin resistance), and the pancreas may not make enough to keep up. Insulin production can decline over time. |
| Share of cases | A minority of people with diabetes. | About 90 to 95 percent of people with diabetes (ADA, NIDDK). |
| Usual age at diagnosis | Often children and young adults, but it can appear at any age. | Most often adults, but it can develop at any age, including in children. |
| How fast symptoms appear | Can appear suddenly over weeks or months and can be severe (CDC). | Often develop over several years; some people have no symptoms (CDC). |
| Insulin | Daily insulin is needed to stay alive (NIDDK). | Many people do not start on insulin; some need it later. Treatment is set by the care team. |
| Known risk factors | Family history and other factors are studied, but lifestyle does not cause it. | Overweight or obesity, family history, inactivity, age and others (NIDDK, ADA). |
| Prevention | There is no proven way to prevent it. | Lifestyle programs can lower the risk in people with prediabetes (ADA, CDC). |
| Emergency to know | Diabetic ketoacidosis (DKA) can be the first sign. | DKA is less common but possible; very high glucose can also be dangerous. |
Table summarizes NIDDK, CDC and ADA descriptions in our own words. Individual cases vary, and your care team decides your treatment.
What they share
- Both raise blood glucose. Over years, high glucose can harm the eyes, kidneys, nerves and heart.
- Both are diagnosed with the same blood tests. See the A1C chart and the blood sugar chart.
- Both benefit from support. Diabetes education, healthy eating and activity matter for each.
Other types
Gestational diabetes, LADA, MODY and type 3c are covered on types of diabetes. If you notice symptoms, read signs of diabetes and ask for testing. If you were just told you have type 2, see newly diagnosed with type 2.
Frequently asked questions
What is the main difference between type 1 and type 2 diabetes?
In type 1, the immune system destroys the cells that make insulin, so the body makes little or none. In type 2, the body does not use insulin well and may not make enough. The NIDDK and ADA describe both.
Can type 2 turn into type 1?
No. They are different conditions. Some adults diagnosed with type 2 are later found to have an autoimmune form, such as LADA, which the ADA classifies with type 1. See the types of diabetes page.
Which type is more common?
Type 2 accounts for about 90 to 95 percent of cases, according to the ADA and NIDDK.
Is one type worse than the other?
Both can lead to serious complications if glucose stays high, and both can be managed. They need different treatment, so the right diagnosis matters.
How are they diagnosed?
The same blood tests are used: an A1C of 6.5% or higher, a fasting glucose of 126 mg/dL or higher, a 2-hour value of 200 mg/dL or higher, or a random glucose of 200 mg/dL or higher with symptoms. Your clinician may add antibody tests to tell the type.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- NIDDK: What Is Diabetes? (reviewed April 2023)
- NIDDK: Type 1 Diabetes
- NIDDK: Type 2 Diabetes
- CDC: Symptoms of Diabetes (May 2024)
- ADA Standards of Care in Diabetes—2026, Section 2: Diagnosis and Classification
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
