One or more of the following tests are used to diagnose diabetes.

Hemoglobin A1c (HbA1c) Test

The HbA1c or A1c is a blood glucose test that is used to monitor diabetes every 3 months. An A1c reading of 6.5% or more means the person has diabetes.

Fasting Blood Glucose Testing

Blood is drawn after the person has had nothing to eat or drink, except water, for 8 hours. Blood glucose is measured in units called milligrams per deciliter (mg/dL). A normal fasting blood glucose level is 100 mg/dL or less. A person has diabetes when two fasting blood glucose levels measure 126 mg/dL or higher.

Oral Glucose Tolerance Test

In this test, a blood sample is taken before a person drinks a sugary beverage. Blood is taken again 2 hours after. This test happens when a person has normal fasting blood glucose but has symptoms of pre-diabetes or type 2 diabetes. A blood glucose of over 126 mg/dL means the person has diabetes.  This test is less common for diagnosis in older adults.

Non-fasting Blood Glucose Test

If a person has diabetes symptoms or risk, a healthcare professional might do a simple blood test by taking a drop of blood from the person’s finger. Glucose is also part of routine bloodwork so diabetes could be diagnosed even if the person has no symptoms. A glucose level of 200 mg/dL or higher usually means diabetes. 

Last Updated April 2023