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Diagnostic Tests

Diagnostic Tests

Diabetes is diagnosed by a blood test. If your healthcare provider thinks you may have diabetes he or she may request one of three blood tests to find out for sure if you have diabetes.

1. Fasting blood sugar. A person with pre-diabetes will have a fasting blood sugar between 100-125mg/dL. A person with diabetes will have a fasting blood sugar of 126mg/dL or greater. This is the easiest way to check for diabetes.

2. Oral Glucose Tolerance Test (OGTT). This test measures your body’s response to sugar. You are given a drink with a very high amount of sugar. Then your blood sugar levels are tested every 60 minutes for up to three hours. The 2 hour reading is often used to diagnose diabetes.

3. Random blood sugar. A random blood sugar test measures your blood sugar at any point in time. It can be after you eat, in the middle of the day or in the evening.

Blood Test

Without Diabetes

With Pre-Diabetes

With Diabetes

Fasting Blood Sugar

Less than 100mg/dl


126mg/dL or greater

Oral Glucose Tolerance Test  (OGTT)

Less than 140mg/dL after 2 hours

Between 140-199mg/dL after 2 hours

200mg/dL or greater, after 2 hours

Random Blood Sugar

Less than 140mg/dL

Between 140-199mg/dL

200 mg/dL or greater