From A1C to OGTT, here’s how diabetes is diagnosed—and how to prevent type 2 if you’re at risk
How Is Diabetes Diagnosed?
There are multiple tests used to diagnose diabetes and prediabetes. Typically, these are repeated on a second day for confirmation, unless your blood glucose is very high or you show classic symptoms such as excessive thirst, urination, fatigue, or weight loss.
All testing should be done in a medical setting—your doctor may recommend one or more of the following:
1. A1C Test (Glycated Hemoglobin)
The A1C test measures your average blood glucose over the past 2–3 months. It’s convenient—no fasting required.
- Normal: Less than 5.7%
- Prediabetes: 5.7% – 6.4%
- Diabetes: 6.5% or higher
✅ Advantage: Easy, non-fasting, reliable for long-term glucose trends
2. Fasting Plasma Glucose (FPG) Test
The FPG test measures blood glucose after at least 8 hours of fasting (usually done in the morning).
- Normal: Less than 100 mg/dL
- Prediabetes: 100–125 mg/dL
- Diabetes: 126 mg/dL or higher
🕗 Tip: Avoid food or drinks (except water) for 8 hours before this test
3. Oral Glucose Tolerance Test (OGTT)
This test checks how your body handles glucose. Your blood is tested:
- Fasting, then
- Two hours after drinking a glucose-rich drink
- Normal: Less than 140 mg/dL
- Prediabetes: 140–199 mg/dL
- Diabetes: 200 mg/dL or higher
🍹 Often used in pregnancy to screen for gestational diabetes
4. Random (Casual) Plasma Glucose Test
This test measures blood sugar at any time of day, regardless of food or drink.
- Diabetes is diagnosed at 200 mg/dL or higher if symptoms are present
⚠️ Used mainly in urgent cases where symptoms are obvious and immediate action is required
What Is Prediabetes?
Prediabetes is a condition where blood sugar is elevated, but not yet in the diabetic range. It’s a critical warning sign that you’re at risk of developing type 2 diabetes and heart disease.
- No obvious symptoms—many people don’t know they have it
- Usually discovered during diabetes screening
🧪 You should be tested every 1–2 years if diagnosed with prediabetes
Indicators of Prediabetes:
| Test | Prediabetes Range |
|---|---|
| A1C | 5.7% to 6.4% |
| FPG | 100–125 mg/dL |
| OGTT (2-hr) | 140–199 mg/dL |
Can You Prevent Type 2 Diabetes?
Yes—prediabetes does not guarantee you’ll develop diabetes. In fact, early intervention can return your blood sugar to normal.
Research-backed ways to lower your risk by 58%:
- ✅ Lose 7% of your body weight
(If you weigh 200 lbs, aim for 15 lbs) - ✅ Exercise moderately for 150 minutes/week
(e.g., 30 minutes/day, 5 days/week)
🎯 Even 10–15 lbs weight loss can have a major impact on your future health.
Key Takeaways
- There are four primary tests to diagnose diabetes: A1C, FPG, OGTT, and Random Glucose.
- Prediabetes often shows no symptoms—but early diagnosis gives you a chance to reverse it.
- Weight loss, diet, and exercise are your strongest tools to prevent or delay type 2 diabetes.
- Work closely with your doctor or diabetes educator to monitor your glucose levels regularly.
Diabetes can be diagnosed using the A1C, FPG, OGTT, or random glucose test. Prediabetes indicates elevated blood sugar and increased diabetes risk—but it can be reversed with early lifestyle changes. Monitoring and prevention are key to long-term health.
