MedDroidLab test guide
Glucose Tolerance Test (OGTT): normal range & what your result means
Written & medically reviewed by Dr. Sanjay Anbu, MBBS · Last reviewed
Medically reviewedIn an oral glucose tolerance test, your blood sugar is checked fasting and again 2 hours after drinking a standard glucose drink. It shows how well your body handles sugar.
About the test
Why the OGTT test is done
- Diagnosing diabetes or prediabetes when other results are borderline
- Screening for diabetes in pregnancy (gestational diabetes)
- Women with PCOS or people with strong family history
Reference range
Typical adult range
| Measure | Typical adult range |
|---|---|
| Fasting, normal | Below 100 mg/dL |
| 2-hour, normal | Below 140 mg/dL |
| 2-hour, prediabetes (IGT) | 140–199 mg/dL |
| 2-hour, diabetes range | 200 mg/dL or more |
| Fasting, diabetes range | 126 mg/dL or more |
Typical adult range; labs differ — use the range on your report. Ranges also vary with age, sex, pregnancy and the method used. Your doctor interprets the result alongside your symptoms and history.
Results
What a HIGH result can mean
- 2-hour value 140–199 mg/dL: impaired glucose tolerance (prediabetes)
- 2-hour value 200 mg/dL or more: in the diabetes range — usually confirmed with a repeat test
- In pregnancy, lower cut-offs are used; your obstetrician will interpret
Results
What a LOW result can mean
- Very low readings during the test are uncommon and should be discussed with your doctor
Preparation
Before the test
- Fast overnight (8–12 hours); water is allowed
- Eat normally in the days before — do not cut carbohydrates
- Stay seated and do not smoke or eat during the 2 hours
Red flags
When to get urgent help
- Shakiness, sweating or confusion during the test — tell the lab staff at once
- Very high sugar with vomiting, drowsiness or fast breathing — seek urgent care
Explore more
Related pages
References
Sources & further reading
Frequently asked questions
What is a normal OGTT result?
For non-pregnant adults, a fasting value below 100 mg/dL and a 2-hour value below 140 mg/dL are typical. Your lab’s range and your doctor’s reading apply.
Why is the OGTT done in pregnancy?
To detect gestational diabetes, which can affect both mother and baby. Different cut-offs are used in pregnancy.
Can I drink water during the OGTT?
Small sips of plain water are usually allowed. Avoid food, tea, coffee, smoking and exercise until the test is complete.