Diagnostic Tests for Type 2 Diabetes

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Type 2 Diabetes Test

Type 2 diabetes is a condition in which the body cannot properly use glucose in the blood for energy, leading to high blood glucose levels. There are many tests the doctor can use to diagnose diabetes, including Type 2 diabetes.

Hemoglobin A1c

The hemoglobin A1c test, also known as glycated hemoglobin, HbA1c or A1C, indicates the percentage of hemoglobin molecules that have glucose attached to them. The HbA1c value indicates the average blood glucose levels over the previous two to three months. An HbA1c level of 6.5 percent or higher indicates diabetes.

Fasting plasma glucose

A fasting plasma glucose (FPG) test is a test of the plasma glucose level after a period of fasting (with no food or drink other than water) for a period of at least 8–10 hours. An FPG level of 126 mg/dl or above strongly suggests diabetes, and the diagnosis can be confirmed by a second FPG level of 126 mg/dl or higher, measured on a different day.

Random plasma glucose

A random plasma glucose (RPG) test is a test of plasma glucose given at any given time, without fasting. A diagnosis of diabetes is made if the plasma glucose level is 200 mg/dl or higher and is accompanied by classic symptoms of diabetes — namely, frequent urination, intense thirst, blurred vision, unexpected weight loss and extreme fatigue.

Oral glucose tolerance test

The oral glucose tolerance test (OGTT) is a plasma glucose test taken after the patient drinks a solution containing 7 grams of glucose following an overnight fast. If the plasma glucose level two hours after the glucose drink is 200 mg/dl or higher, the patient is diagnosed with diabetes.


Prediabetes is a condition in which the blood glucose levels are high, but not high enough to qualify for diabetes, and people with prediabetes are at risk for developing full-blown Type 2 diabetes in the future. An FPG level greater than 100 mg/dl but less than 126 mg/dl may indicate prediabetes. So may a plasma glucose level of 140 mg/dl to 199 mg/dl two hours after the start of an OGTT test or an HbA1c of 5.7 to 6.4 percent.

Want to learn more about Type 2 diabetes? Read “Diabetes Research: What’s New,” “Type 2 Diabetes and a Healthy Family Lifestyle” and “Prediabetes: What to Know.”

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