Test & Diagnosis of Diabetes

According to the American Diabetes Association, a few different tests may be used for screening and diagnosis of diabetes or prediabetes and each test has advantages, disadvantages, and limitations. If the initial screening result from one of the tests listed below is abnormal, the test is repeated on another day. The repeat result must be abnormal to confirm a diagnosis of diabetes. Tests include:

The FPG (Fasting Plasma Glucose)

This test checks your fasting blood glucose levels. Fasting means after not having anything to eat or drink (except water) for at least 8 hours before the test. This test is usually done first thing in the morning, before breakfast.

>> Diabetes is diagnosed at fasting blood glucose of greater than or equal to 126 mg/dl

FPG LevelIndication
 From 70 to 99 mg/dL Normal
 From 100 to 125 mg/dL Prediabetes
 126 mg/dL and above Diabetes


The OGTT (Oral Glucose Tolerance Test)

The OGTT is a two-hour test that checks your blood glucose levels before and 2 hours after you drink a 75-gram glucose drink. It tells the doctor how your body processes glucose.

>> Diabetes is diagnosed at 2 hour blood glucose of greater than or equal to 200 mg/dl
OGTT LevelIndication
 Less than 140 mg/dL Normal
 From 140 to 199 mg/dL Prediabetes
 Equal to or greater than 200 mg/dL Diabetes


The A1C (Hemoglobin A1c)

The A1C test measures your average blood glucose for the past 2 to 3 months. The advantages of being diagnosed this way are that you don’t have to fast or drink anything.

>> Diabetes is diagnosed at an A1C of greater than or equal to 6.5%
A1c LevelIndication
 Less than 5.7% Normal
 5.7% to 6.4% Prediabetes
 6.5% or higher Diabetes


Random (also called Casual) Plasma Glucose Test


This test is a blood check at any time of the day when you have severe diabetes symptoms.

>> Diabetes is diagnosed at blood glucose of greater than or equal to 200 mg/dl