Glucose Tolerance Test (3 Samples)

Function

The Glucose Tolerance Test (GTT) is a gold-standard diagnostic tool used to evaluate how the body metabolizes glucose. It measures the body's ability to clear a specific concentrated dose of glucose from the bloodstream over a set period. By taking three samples (usually fasting, 1-hour post-ingestion, and 2-hours post-ingestion), clinicians can observe the kinetics of insulin response and glucose disposal.

Why it is Ordered

This test is primarily ordered to diagnose Gestational Diabetes Mellitus (GDM) in pregnant women, typically between 24 and 28 weeks of gestation. It is also used to identify Prediabetes or Type 2 Diabetes when fasting plasma glucose levels are inconclusive but clinical suspicion remains high. It helps in identifying 'impaired glucose tolerance,' a state where blood sugar is high but not yet at the threshold of overt diabetes.

Associated Conditions

• Gestational Diabetes: High levels during pregnancy that increase risks for both mother and child.
• Insulin Resistance: A condition where cells do not respond properly to insulin.
• Metabolic Syndrome: A cluster of conditions that increase the risk of heart disease and stroke.
• Polycystic Ovary Syndrome (PCOS): Often associated with insulin processing issues.
• Reactive Hypoglycemia: Where blood sugar drops to abnormally low levels after a glucose load.

Procedure and Expectations

Patients must fast for 8–12 hours. A baseline blood sample is drawn, followed by the consumption of a standardized glucose drink (usually 75g or 100g). Subsequent blood draws occur at intervals to map the glycemic curve. This longitudinal view is far more descriptive than a single static measurement.