Oral Glucose Tolerance Test (OGTT)
The oral glucose tolerance test (OGTT) measures how well your body handles a standard dose of sugar over two hours — the gold standard for diagnosing prediabetes and diabetes.
Plain English
Patient-Friendly Explanation
The oral glucose tolerance test checks how efficiently your body moves sugar out of your blood. You fast overnight, have blood drawn, drink a sweet glucose drink, then have blood drawn again one and two hours later. If your blood sugar stays high after the drink, it means your body is struggling to handle sugar — which points to prediabetes or diabetes.
Medical
Clinical Definition
The OGTT involves a fasting plasma glucose measurement followed by ingestion of 75 g anhydrous glucose, with plasma glucose sampled at 120 minutes (WHO criteria). A 2-hour glucose ≥ 11.1 mmol/L confirms diabetes; 7.8–11.0 mmol/L indicates impaired glucose tolerance (IGT). In Asian populations, where postprandial hyperglycaemia is common, OGTT frequently detects dysglycaemia missed by fasting glucose alone. It also has a role in evaluating reactive hypoglycaemia and in screening for gestational diabetes (with a 50 g or 75 g protocol).
Key Insight
Why It Matters
Fasting blood sugar alone can miss early diabetes, especially in Asian patients — so a two-hour glucose tolerance test is part of thorough metabolic assessment at Accord Medical.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
