Why get tested
Prediabetes and type 2 diabetes often cause no symptoms, so testing is how they're found. (Type 1 is different: symptoms can come on quickly and be severe.) If you have any risk factors, ask your doctor about screening — testing before symptoms appear.
- Catching prediabetes early can prevent or delay type 2 diabetes.
- Finding type 2 diabetes and acting on it can prevent or delay serious complications.
- It's simple: blood is drawn at a doctor's office or clinic, and results usually come back quickly.
Who gets which tests
- Prediabetes and type 2: ask about testing if you have risk factors. If a health fair or pharmacy test was high, follow up with your doctor, who may retest to confirm.
- Type 1: if your doctor suspects it or you're at high risk, your blood may be tested for autoantibodies — signs the body is attacking itself, common in type 1 but not type 2. Autoantibody testing can find early-stage type 1, which can be treated before symptoms and complications. Your urine may be tested for ketones, made when the body burns fat for energy; ketones point to type 1 rather than type 2.
- Gestational diabetes: it usually develops around the 24th week of pregnancy, so testing is typically between 24 and 28 weeks — earlier if you're at higher risk. High blood sugar early in pregnancy may mean type 1 or type 2 diabetes instead.
Reading the results
| Test | What it measures | Normal | Prediabetes | Diabetes |
|---|---|---|---|---|
| A1C | average blood sugar over the past 2 or 3 months | below 5.7% | 5.7–6.4% | 6.5% or above |
| Fasting blood sugar | blood sugar after an overnight fast | 99 mg/dL or below | 100–125 mg/dL | 126 mg/dL or above |
| Glucose tolerance (at 2 hours) | blood sugar before and after a glucose drink, after an overnight fast; checked at 1, 2 and possibly 3 hours | 140 mg/dL or below | 140–199 mg/dL | 200 mg/dL or above |
| Random blood sugar | blood sugar at any time, no fasting | — | — | 200 mg/dL or above |
Other tests:
- Autoantibody test: type 1 diabetes happens when the immune system makes autoantibodies that destroy the pancreas's insulin-making cells. A blood test finds them. Type 1 develops in three stages, defined by how many autoantibodies are present, whether blood sugar is normal, and whether there are symptoms.
- Glucose screening test (pregnancy): drink a glucose liquid and have blood drawn 1 hour later. 140 mg/dL or lower is normal; above that, you'll need a glucose tolerance test.
Results can vary with the size of the glucose drink and how often blood is tested — ask your doctor what your results mean.
After a diagnosis
If you have type 1, type 2 or gestational diabetes, work out a detailed treatment plan with your doctor, including referrals to:
- diabetes self-management education and support;
- an endocrinologist (a specialist in hormone-related conditions) — early-stage type 1 can be treated to avoid or delay symptoms and complications;
- a registered dietitian.
See also: living with diabetes.
Sources
Based on "Diabetes Testing," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
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Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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