Diagnostics
How diabetes is diagnosed — and how doctors figure out which type.
Getting a diagnosis can feel like a lot at once. Here’s what tests are usually done, what they’re looking for, and how doctors decide between type 1, type 2, and MODY.
When testing matters
The most important step is to think about diabetes when symptoms appear, and to get tested. The different types can overlap in how they look, so testing is what tells them apart.
📋 Worth knowing
The American Diabetes Association recommends screening young people (age 10 and up) for type 2 diabetes if they have risk factors — even when there are no obvious symptoms.
Steps for diagnosing diabetes
Most diagnoses come from a combination of these tests, plus a physical exam.
💧 Urine glucose test
Checks for glucose and ketones in urine. Often the first quick check.
🩸 Blood glucose test
Measures sugar directly in your blood. It can be done two ways:
- Fasting — before you eat in the morning. Diabetes if ≥ 126 mg/dL.
- Random — anytime, regardless of when you last ate. Diabetes if ≥ 200 mg/dL.
📊 HbA1c (hemoglobin A1c)
Shows your average blood sugar over the past 2–3 months. In diabetes, HbA1c is usually ≥ 6.5%. Especially helpful for spotting type 2 when symptoms are mild or unclear.
🧪 Oral glucose tolerance test
Used when symptoms are absent or unusual. You drink a sugary liquid and your blood sugar is checked over time. Values above 200 mg/dL after the drink suggest diabetes.
After a physical exam and these tests, your doctor can usually tell you whether you have diabetes — and which type is most likely.
Telling type 1 and type 2 apart
Doctors look for antibodies in the blood — these are markers from the immune system attacking insulin-producing cells.
🩸 Antibodies present
Points to type 1 diabetes. The immune system is involved in damaging the cells that make insulin.
🔵 Antibodies absent
More likely type 2 diabetes. Your body still makes insulin, but isn’t using it well.
What about MODY?
Maturity-Onset Diabetes of the Young — about 1.2% of diabetes cases in minors in the U.S.
🧬 What doctors look for
- Strong family history of mild hyperglycemia or clear diabetes across at least 3 consecutive generations, including 1st-degree relatives
- Diagnosis before age 25
- No autoantibodies against insulin-producing cells
- Positive C-peptide in the blood (insulin is still being made)
- No type 2 signs like obesity or insulin resistance
🔬 Genetic testing
A definite MODY diagnosis can only be made through genetic testing. Doctors usually test for several known gene mutations. The most common types are MODY 2 and MODY 3.
💡 What to take from this
If you or someone you love might have diabetes, the path is the same: notice the signs, get tested, and let the results guide which type you’re living with. Each type has its own management — but the diagnosis is what unlocks the right plan.
TeenHealthInsight is a health education website — not a substitute for medical advice. Any questions or worries about your medication, devices, or daily care should be brought to your doctor. Learn here, decide there — always loop in your diabetes team before changing anything you do.