Oral Glucose Tolerance Test (OGTT) - Blood Glucose Measurement

Why This Test Is Done

Your doctor may recommend an oral glucose tolerance test if you have symptoms of diabetes, such as frequent urination, excessive thirst, unexplained weight loss, or fatigue. It’s also used to screen for gestational diabetes during pregnancy or to diagnose prediabetes or type 2 diabetes in adults.

What to Expect During the Test

You’ll start by fasting for at least 8 hours before the test. A blood sample is taken first (usually from your arm) to measure your baseline blood sugar. Then, you’ll drink a sweet liquid containing glucose. Follow-up blood samples are drawn at set intervals (typically 30 minutes, 1 hour, 2 hours) to check how your blood sugar responds.

Understanding Your Results

Blood glucose levels are measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). Your doctor will compare your results to standard ranges to determine if your blood sugar is within normal limits, borderline, or elevated.

Preparing for the Test

Avoid eating or drinking anything except water for 8 hours before your test. Wear comfortable clothing and bring any medications you take daily with you. If you’re pregnant, let your doctor know before the test.