Criteria for Diagnosing Diabetes
- Have symptoms of diabetes (increased thirst, increased urination, and unexplained weight loss) and a blood sugar level equal to or greater than 200 milligrams per deciliter (mg/dL). The blood sugar test is done at any time, without regard for when you last ate (random plasma glucose test or random blood sugar test).
- Have a fasting blood sugar level that is equal to or greater than 126 mg/dL. A fasting blood sugar test (fasting plasma glucose) is done after not eating or drinking anything but water for 8 hours.
- Have a 2-hour oral glucose tolerance test (OGTT) result that is equal to or greater than 200 mg/dL. An OGTT is most commonly done to check for diabetes that occurs with pregnancy (gestational diabetes).
- Have a hemoglobin A1c that is 6.5% or higher. This test is most reliable for adults. Some experts recommend using one of the other tests to diagnose diabetes in children.footnote 1 This test may not be appropriate for everyone because many things can affect the life span of red blood cells, such as the second or third trimester of pregnancy, a recent blood loss or a blood transfusion, sickle cell disease, hemodialysis, or erythropoietin (ESA) medicine.
Your doctor may repeat the test to confirm the diagnosis of diabetes.
If the results of your fasting blood sugar test are between 100 mg/dL and 125 mg/dL, your OGTT result is between 140 to 199 mg/dL (2 hours after the beginning of the test), or your hemoglobin A1c is 5.7% to 6.4%, you have prediabetes. This means that your blood sugar is above normal but not high enough to be diabetes. Discuss with your doctor how often you need to be tested.footnote 1
Current as ofJuly 25, 2018
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Adam Husney, MD - Family Medicine
Matthew I. Kim, MD - Endocrinology, Diabetes and Metabolism
David C. W. Lau, MD, PhD, FRCPC - Endocrinology
Current as of: July 25, 2018