Aging & Health A to Z
Diagnosis & Tests
Finding diabetes early is essential to your health. The sooner you begin treating it, the easier it will be to avoid serious problems later on.
Diagnosis is simple. Your healthcare professional will use a blood test to check the level of glucose (sugar) in your blood.
Blood Glucose Testing
Blood glucose is measured in units called milligrams per deciliter or mg/dL. A normal blood glucose level is 100 mg/dL or less, after you’ve had no food or liquids (except water) for 8 hours (called fasting blood glucose).
Fasting Plasma Glucose Test
Blood is drawn after you’ve had nothing to eat or drink (except water) for 8 hours. The test is usually repeated a second time. Diabetes is diagnosed 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 drinking a sugary beverage, and again 2 or 3 hours afterward. This test is usually used if your fasting blood glucose test was normal, but your symptoms make your healthcare professional suspect that you have type 2 diabetes or pre-diabetes.
Casual or Random (non-fasting) Blood Glucose Test
If you have diabetes symptoms or risk factors, your healthcare professional might perform this simple in-office blood test by taking a drop of blood from your finger. You don’t need to fast before the test. A glucose level of 200 mg/dL or higher usually indicates diabetes.
Medications can sometimes raise your blood sugar, so give your healthcare professional a complete list of everything you’re taking--prescriptions, over-the-counter medications, vitamins, herbal and other supplements--before your blood test.
Updated: March 2012
Posted: March 2012