OGTT result interpretation
| 2-Hour Result | Category |
|---|---|
| <140 mg/dL (<7.8 mmol/L) | Normal |
| 140–199 mg/dL (7.8–11.0 mmol/L) | Impaired glucose tolerance (pre-diabetes) |
| ≥200 mg/dL (≥11.1 mmol/L) | Diabetes mellitus |
How the OGTT is performed
Step-by-step procedure
1. Fast for 8–12 hours (water is allowed). 2. A fasting blood glucose is taken. 3. You drink a solution containing 75g of glucose (dissolved in 250–300 mL of water) within 5 minutes. 4. Blood glucose is measured again at 1 hour and 2 hours after the drink. During the test, you must remain seated and not eat, drink (except water), smoke or exercise. The test usually takes about 2 hours in a clinic or lab.
Gestational diabetes OGTT
| Time point | Threshold (75g OGTT) |
|---|---|
| Fasting | ≥92 mg/dL (5.1 mmol/L) |
| 1 hour | ≥180 mg/dL (10.0 mmol/L) |
| 2 hours | ≥153 mg/dL (8.5 mmol/L) |
For gestational diabetes, one abnormal value is sufficient for diagnosis. The test is routinely offered at 24–28 weeks of pregnancy.
Who needs an OGTT?
- Pregnant women at 24–28 weeks (gestational diabetes screening)
- People with borderline fasting glucose (100–125 mg/dL)
- People with risk factors for diabetes — obesity, family history, PCOS
- Confirming pre-diabetes when HbA1c is borderline
Medical Disclaimer: For educational purposes only. Always consult a qualified healthcare professional for diagnosis and treatment.