Diagnosis & Tests
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
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