Gestational diabetes is high blood sugar that starts during pregnancy, and it’s usually found with a glucose drink test between 24 and 28 weeks. Most people manage it with food changes and activity, and blood sugar usually goes back to normal after birth, but it raises your chance of type 2 diabetes later, so the follow-up tests matter as much as the pregnancy ones.
In the US, 5% to 9% of pregnancies are affected each year, according to the CDC. It happens because pregnancy hormones make the body more resistant to insulin. For some people, the pancreas can’t keep up. It isn’t caused by something you did wrong, and it’s very treatable.
Who is more likely to get gestational diabetes?
The NHS lists these risk factors:
- A BMI above 30
- A previous baby weighing 4.5 kg (10 lb) or more
- Gestational diabetes in a past pregnancy
- A parent, brother or sister with diabetes
- South Asian, Black, African-Caribbean or Middle Eastern family origin
- Being over 40
- Past gastric bypass or other weight-loss surgery
Many people with gestational diabetes have no symptoms at all. That’s why testing, not waiting for symptoms, is how it gets picked up.
How is gestational diabetes tested? It depends on your country
All three approaches below use a sweet glucose drink and a blood test. What differs is who gets tested, if you need to fast, and how many blood draws there are.
| Country | Who is tested | The test |
|---|---|---|
| US | Usually all pregnant people, at 24 to 28 weeks (earlier if higher risk) | Often a two-step approach: a 1-hour glucose challenge test (no fasting), then a longer 3-hour fasting test only if the first result is high. Some clinics use a single 2-hour test instead. |
| UK | People with one or more risk factors, checked at booking (8 to 12 weeks) | A 2-hour oral glucose tolerance test (OGTT) at 24 to 28 weeks, after fasting. If you had gestational diabetes before, an earlier test soon after booking too. |
| India | All pregnant women, at the first antenatal visit and again at 24 to 28 weeks if the first is normal | A single-step test: 75 g glucose in about 300 ml water, fasting or not, with one blood sample 2 hours later. A result of 140 mg/dL (7.8 mmol/L) or more means gestational diabetes. |
The US details come from the Cleveland Clinic and the CDC, the UK details from the NHS, and the India test from the Ministry of Health’s national guidelines on gestational diabetes. The exact cut-off values for the US and UK tests vary by guideline and lab, so ask your midwife or doctor which numbers they use.
A tip for the fasting tests: you’ll usually sit quietly at the clinic for the full two or three hours. Bring water (if allowed), something to read and a snack for afterwards.
Blood sugar targets once you’re diagnosed
You’ll be given a meter and asked to check your blood sugar at home, usually first thing in the morning and after meals. The targets your team gives you are the ones to follow. As a guide, the Cleveland Clinic lists these targets based on American College of Obstetricians and Gynecologists guidance:
| When you test | Target |
|---|---|
| Before a meal (including fasting, on waking) | 95 mg/dL (5.3 mmol/L) or less |
| 1 hour after a meal | 140 mg/dL (7.8 mmol/L) or less |
| 2 hours after a meal | 120 mg/dL (6.7 mmol/L) or less |
UK clinics usually work in mmol/L and test 1 hour after meals. If you’re not sure whether to use the 1-hour or 2-hour target, ask. Mixing them up is a common reason for confusing readings.
What to eat with gestational diabetes
The basic advice from the NHS treatment page is simple:
- Eat regularly, usually three meals a day, and don’t skip meals.
- Choose starchy foods with a low glycaemic index (GI), such as wholewheat pasta, brown rice and pulses.
- Eat at least five portions of fruit and vegetables a day.
- Swap sugary snacks and drinks for healthier or sugar-free options.
Some easy changes that follow the advice above:
- Breakfast: eggs or plain yoghurt with nuts and a small portion of oats, instead of sugary cereal, white toast with jam or fruit juice.
- Lunch and dinner: half the plate vegetables, a quarter protein (fish, chicken, dal, beans, tofu, paneer), a quarter wholegrain or low-GI carbs (brown rice, wholewheat roti, wholemeal pasta, barley).
- Snacks: a piece of fruit with a handful of nuts, roasted chickpeas, cheese with wholegrain crackers.
- Drinks: water, milk, unsweetened tea. Avoid juice and regular soft drinks, which push blood sugar up fast.
Your meter is your best guide. If a particular meal keeps giving high readings, try a smaller carb portion or a lower-GI swap next time. Our comparison of oats, barley, quinoa and millets for blood sugar may help with ideas. Don’t cut carbs right out. You and the baby still need them, and pregnancy is not the time for a strict low-carb or weight-loss diet.
Exercise and when medicine is needed
Activity lowers blood sugar. The NHS suggests aiming for at least 150 minutes of moderate activity a week, plus strength exercises on two or more days, if your pregnancy allows it. A 10 to 15 minute walk after meals is a practical way to bring down post-meal readings.
If blood sugar stays high 1 to 2 weeks after changing diet and activity, or is very high at diagnosis, the NHS says medicine is usually added. That’s often metformin tablets, or insulin injections if metformin isn’t suitable or isn’t enough. Needing medicine doesn’t mean you’ve failed. Pregnancy hormones rise as the weeks go on, and many people need help later in pregnancy no matter how carefully they eat.
Why it matters for the baby and the birth
When blood sugar is well controlled, most pregnancies have good outcomes. Without control, the main concerns listed by the Cleveland Clinic are a larger baby, breathing problems at birth, low blood sugar in the newborn, premature birth, and a higher chance of obesity and type 2 diabetes for the child later in life.
Because of this, you’ll usually have extra scans to check the baby’s growth. The NHS says the ideal time to give birth is usually around 38 to 40 weeks, and if you haven’t given birth by 40 weeks and 6 days, you’ll usually be offered induction or a caesarean section.
After the birth: your later risk of type 2 diabetes
This is the part many people skip. Blood sugar usually returns to normal soon after delivery, but the risk doesn’t disappear. The CDC says about half of women with gestational diabetes go on to develop type 2 diabetes.
Follow-up testing differs by country:
- UK: a diabetes blood test 6 to 13 weeks after giving birth, then once a year if normal.
- India: a repeat glucose tolerance test at 6 weeks after delivery, with ongoing checks through NCD clinics.
- US: the CDC advises asking your doctor how often you should have your blood sugar checked.
The yearly test is often an HbA1c. Our guide to HbA1c vs fasting blood sugar explains what the numbers on that report mean, and our article on prediabetes signs and test numbers covers the in-between range.
The good news is that the risk can be lowered. In the US Diabetes Prevention Program, women with a past history of gestational diabetes who followed an intensive lifestyle programme cut their progression to diabetes by 35% over 10 years compared with placebo, and those on metformin by 40% (Aroda and colleagues, Journal of Clinical Endocrinology and Metabolism, 2015). The lifestyle programme focused on modest weight loss and regular activity.
If you plan another pregnancy, tell your team early. You’ll usually be offered an earlier glucose test, because having had gestational diabetes before is one of the main risk factors.
When to see a doctor
Contact your midwife, obstetrician or diabetes team promptly if:
- Your readings are above target more than once or twice in a few days, even with food changes
- You’re very thirsty, peeing a lot more than usual, or have a very dry mouth
- You’re on insulin and have shakiness, sweating, confusion or a fast heartbeat (signs of low blood sugar). Have a sugary drink and check your level.
- After the birth, you notice thirst, frequent urination, tiredness or blurred vision. Don’t wait for your next routine test.
Get emergency help if you notice your baby moving less than usual, have heavy bleeding, a severe headache with vision changes or swelling of the face and hands, or you’re on insulin and become drowsy or confused and can’t treat a low yourself. Call your maternity unit or your local emergency number (911 in the US, 999 in the UK, 112 in the EU and India).
Frequently asked questions
Can I refuse the glucose test?
You can, but because gestational diabetes often has no symptoms, the test is the only reliable way to find it. If the sugary drink makes you feel unwell, tell your midwife or doctor and ask what alternatives your clinic offers.
Will my baby be born with diabetes?
No. Gestational diabetes doesn’t mean the baby has diabetes. The baby’s blood sugar is checked after birth because it can drop for a short time after birth.
Is fruit allowed with gestational diabetes?
Yes. Whole fruit is part of the NHS advice. Spread it through the day, eat it with a protein such as nuts or yoghurt, and avoid fruit juice and smoothies.
Does gestational diabetes go away after birth?
Usually, yes. Blood sugar tends to return to normal soon after delivery. You still need the follow-up test, because your risk of type 2 diabetes stays higher for years.
Can I prevent gestational diabetes in my next pregnancy?
Not always, but your chances improve if you reach a healthy weight before you conceive, eat well and stay active. The CDC advises not trying to lose weight while pregnant.
This article is for general information and is not a substitute for advice from a doctor. If you have symptoms or a health condition, please consult a qualified healthcare professional.
