An Oral Glucose Tolerance Test (OGTT) is a more comprehensive test than a Fasting Plasma Glucose (FPG) test. It measures your blood sugar levels at multiple points in time after you drink a sugary liquid. This helps to see how your body processes sugar over a period of two hours. Here's how the OGTT is typically performed: Fasting: You'll be asked to fast for at least 8 hours before the test. Initial Blood Sample: A healthcare professional will take a sample of your blood to measure your fasting glucose level. Glucose Drink: You'll then drink a liquid containing a specific amount of glucose (usually 75 grams for non-pregnant adults). Subsequent Blood Samples: Blood samples will be taken at specific intervals, usually 1 hour and 2 hours after you finish the drink. The OGTT is often used to diagnose: Prediabetes: When blood sugar levels are higher than normal but not yet in the diabetic range. Type 2 Diabetes: A condition where the body doesn't use insulin properly or doesn't produce enough insulin. Gestational Diabetes: A type of diabetes that develops during pregnancy. Normal OGTT values (for non-pregnant adults): Fasting: 70-99 mg/dL (3.9-5.5 mmol/L) 1 hour: Less than 200 mg/dL (11.1 mmol/L) 2 hours: Less than 140 mg/dL (7.8 mmol/L) Abnormal OGTT values may indicate: Prediabetes: 2-hour value between 140 and 199 mg/dL (7.8 and 11.0 mmol/L) Diabetes: 2-hour value of 200 mg/dL (11.1 mmol/L) or higher It's important to note that the OGTT is a longer test than the FPG and requires multiple blood draws. It's crucial to follow your doctor's instructions carefully to ensure accurate results.