Please book ahead so we can start you early. Call 8872524007.
What the GTT test checks
The oral glucose tolerance test (OGTT) gives everyone the same challenge: 75 g of glucose dissolved in water, as set out by the World Health Organization for adults. Blood glucose is measured before the drink and usually again at two hours. Some protocols, especially in pregnancy, add a one-hour sample.
Because the sugar load is fixed, the result is easier to compare than a PPBS test, where every meal is different.
Why your doctor may order it
- Screening for gestational diabetes, commonly between 24 and 28 weeks of pregnancy, or earlier if risk is high
- Borderline fasting or HbA1c results where the doctor wants a clearer answer
- Women with PCOS, or anyone with a strong family history and normal-looking fasting values
- Investigating episodes of low sugar a few hours after meals (a longer, specialist-ordered version)
How to prepare
- Eat your normal diet, with ordinary amounts of roti, rice and dal, for the three days before. Cutting carbohydrates beforehand can give a falsely abnormal result.
- Fast overnight for 8 to 14 hours. Plain water only.
- Arrive at the lab early, ideally by 8 am, and plan to stay about two and a half hours.
- During the test, sit quietly. No food, no tea, no smoking and no walking around the market.
- Bring something to read, and a snack for after the last sample.
Some people feel a little nauseous after the sweet drink. Tell the staff if you vomit, as the test may need to be repeated another day. If you're pregnant, your doctor may follow the single-step Indian protocol, which can be done without fasting; follow the instructions on your slip. Our blood test preparation guide has more general tips.
Sample type and report time
Each sample goes into a grey fluoride tube. The report, with all time points on one page, is ready the same day after your final sample.
People often search for a GTT test near me hoping for home collection. Because the drink and timed samples need supervision, we do GTT at the lab only. Other tests can still be booked through home sample collection.
Understanding your results
For non-pregnant adults, the American Diabetes Association reads the two-hour value like this:
- Below 140 mg/dL: usual
- 140 to 199 mg/dL: impaired glucose tolerance (prediabetes)
- 200 mg/dL or above: consistent with diabetes
Pregnancy uses lower thresholds, and Indian guidelines (DIPSI) treat a two-hour value of 140 mg/dL or above as gestational diabetes. The range printed on your report is the one that applies; ranges vary by lab and method. Your doctor reads the result alongside your symptoms and other tests.
FAQ
How long does the GTT take?
About two to two and a half hours from the fasting sample, plus a short wait at the start.
Is the GTT safe in pregnancy?
Yes. It's routinely offered in pregnancy and uses a standard amount of glucose. Ask your doctor if you have concerns.
Can I walk around during the test?
Please stay seated. Walking burns glucose and can make your result look better than it really is.
Is the oral glucose tolerance test the same as a sugar test after food?
No. A GTT uses a fixed 75 g glucose drink under controlled conditions; a PPBS uses your own meal.
Book at Alpha Laboratory
To book a GTT test, call 8872524007 a day before, or WhatsApp us. Directions are on our contact page.