Fasting Plasma Glucose (Mass Concentration) Test

Why This Test Matters

Fasting blood sugar tests are critical for diagnosing conditions like type 2 diabetes, prediabetes, or insulin resistance. They also help monitor existing diabetes management. Your doctor may recommend this test if you have symptoms like excessive thirst, fatigue, or unexplained weight changes.

How the Test Works

You’ll fast (not eat or drink anything except water) for 8–12 hours before the test. A blood sample is taken from a vein, usually in your arm, and sent to a lab to measure glucose levels. The test is quick and painless, though you may feel a slight pinch during the draw.

What to Expect Before the Test

Plan ahead: Avoid sugary foods, drinks, or medications containing sugar (e.g., cough syrups) for 24 hours before testing. Wear comfortable clothing with an easy armhole for the blood draw. If you’re pregnant, have diabetes, or take certain medications, let your doctor know.

What the Results Mean

Results are typically reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). While exact ranges vary by lab, results are often categorized as normal, prediabetic, or diabetic. Your doctor will interpret the results in relation to your health history and symptoms.