OGTT in Pregnancy — What It Means
Informational only. Antenatal results should always be discussed with your obstetrician, who interprets them for your specific pregnancy.
The oral glucose tolerance test (OGTT) shows how your body handles a standard glucose drink. Your blood sugar is checked while fasting, then at 1 hour and 2 hours. Pregnancy hormones make your body respond less well to insulin. This peaks in the second trimester. So 24 to 28 weeks is the best window to find pregnancy diabetes (gestational diabetes mellitus, or GDM).
Second trimester
Last reviewed: 2026-08-16
When is it done?
You usually have this between 24 and 28 weeks. It may be done earlier if you have risk factors for pregnancy diabetes.
Why is it done in pregnancy?
Pregnancy hormones make your body respond less well to insulin. This peaks in the second trimester. So 24 to 28 weeks is the best window to find pregnancy diabetes (gestational diabetes mellitus, or GDM).
Trimester-specific ranges
Trimester 2
75 g OGTT thresholds (any ONE value met = GDM): Fasting ≥ 92 mg/dL; 1-hour ≥ 180 mg/dL; 2-hour ≥ 153 mg/dL
Sources: [WHO / IADPSG, 2013]
What to discuss with your obstetrician
Ask your obstetrician which glucose tolerance rules your team uses, WHO/IADPSG or DIPSI. Also ask what your results mean. And ask what monitoring or lifestyle changes are suggested.
Questions to ask your obstetrician
About this result
- What does my OGTT result mean for me and my baby at this stage of pregnancy?
- Is my OGTT being read against a pregnancy-specific range?
What to do next
- Based on my OGTT, is there anything you would suggest I do or change during this pregnancy?
About retesting
- Will my OGTT be checked again later in the pregnancy, and if so, when?
The bigger picture
- How does my OGTT fit with the rest of my antenatal checks?
Frequently asked questions
- Why is the OGTT done specifically around 24–28 weeks?
- Placental hormones make your body respond less well to insulin. Their effect peaks in the second trimester. This is when pregnancy diabetes is most likely to show up. Testing earlier can miss cases that start later.
- What do the three blood draws in the OGTT measure?
- The fasting draw sets the baseline. The 1-hour draw shows the peak sugar rise after the drink. The 2-hour draw shows how well your body clears the glucose. Together they show how your body handles sugar.
- Is the DIPSI one-step test different from the WHO 75 g OGTT?
- Yes, they differ. DIPSI uses a 75 g glucose load and checks only the 2-hour value, with a cut-off of 140 mg/dL or above. It needs no prior fast and is widely used in India for practical reasons. WHO/IADPSG rules instead use three time points, and your obstetrician will say which your clinic follows.
- What should I do on the day of the OGTT?
- Fast for at least 8 hours. Go to your appointment in the morning. Stay seated and avoid hard activity during the test. Drink only water until the last blood draw is done.
- Does a GDM result mean I will have diabetes after pregnancy?
- GDM usually clears after delivery. But it does raise your long-term chance of type 2 diabetes. Your obstetrician will advise on a sugar check after birth. They will also suggest longer-term lifestyle care.
- Can gestational diabetes be managed without insulin?
- Many cases are handled with food changes, suitable activity, and home sugar checks. Insulin or other medicines are added when sugar targets are not met. Your obstetrician and a diabetes care team will guide this.
Sources
- WHO / IADPSG (2013) — Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy, WHO/NMH/MND/13.2
- ADA (2023) — Standards of Medical Care in Diabetes — Gestational Diabetes Mellitus section, Diabetes Care
- DIPSI / FOGSI (2018) — DIPSI Guidelines: Management of GDM in India using a single-step 75 g 2-hour post-glucose value ≥ 140 mg/dL
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