Criteria for diagnosing diabetes

To be diagnosed with diabetes, you must meet one of the following criteria:¹

• 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.

The diagnosis of diabetes needs to be confirmed by repeating the same blood sugar test or doing a different test on another day.

The American Diabetes Association (ADA) recommends the fasting blood sugar test for diagnosing diabetes because it is inexpensive, easy to do, quick, and convenient to use.¹ If the results of your test are between 100 mg/dL and 125 mg/dL, you have prediabetes, meaning your blood sugar is above normal but not high enough to be diabetes. Discuss with your health professional how often you need to be tested.

Some studies have indicated that a hemoglobin A1c or similar test (glycosylated hemoglobin or glycohemoglobin) may be used to diagnose diabetes; however, the ADA does not recommend this test for this purpose. The hemoglobin A1c test estimates the average blood sugar level over the previous 2 to 3 months and is recommended as the test for monitoring blood sugar control after diagnosis.¹

Some health professionals use two blood sugar tests done without regard to when the person last ate (random blood sugar test) if blood sugar levels are within the range for diagnosis of diabetes; however, the ADA does not recommend this method.

Citations

1. American Diabetes Association (2007). Standards of medical care in diabetes. Clinical Practice Recommendations 2007. Diabetes Care, 30(Suppl 1): S4–S41.