This guide provides general information about gestational diabetes in pregnancy.

If you are concerned about symptoms or have been diagnosed, speak with your midwife or diabetes team. Gestational diabetes is very manageable, and most women have healthy pregnancies and babies with the right care. Read more about our approach.

Gestational diabetes: symptoms, testing and management in the UK

What is gestational diabetes?

Gestational diabetes is high blood glucose (sugar) that develops during pregnancy, usually in the second or third trimester. It happens because your body cannot produce enough insulin to meet the extra demands of pregnancy. It is not the same as having diabetes before you were pregnant.

It affects around 1 in 20 pregnancies in the UK and usually resolves within a day or two of giving birth. With proper monitoring and care, the vast majority of women with gestational diabetes have healthy babies and straightforward births. Key things to know include your pre-pregnancy BMI, how gentle exercise after meals helps lower blood sugar, and preparing for your 24-28 week OGTT test.

Who is at higher risk?

  • Age 40 or over
  • BMI above 30
  • Previous baby weighing 4.5kg (10lb) or more at birth
  • Gestational diabetes in a previous pregnancy
  • Parent or sibling with type 2 diabetes
  • South Asian, Black, African-Caribbean or Middle Eastern family background
  • Polycystic ovary syndrome (PCOS)
  • Previous weight-loss surgery (gastric bypass or sleeve)

Even if none of these apply to you, gestational diabetes can still develop. That is why screening is offered routinely when a risk factor is present, and why it is always worth reporting symptoms to your midwife. Use our pregnancy weight gain calculator to check your pre-pregnancy BMI.

Symptoms

Most people have no symptoms at all. Gestational diabetes is usually picked up on a screening blood test, not from how you feel. If blood sugar is very high, some women notice:

  • Increased thirst
  • Needing to pass urine more often than usual
  • Dry mouth and unusual tiredness
  • Blurred vision
  • Genital itching or thrush

Many of these overlap with normal pregnancy symptoms. Do not try to self-diagnose. Discuss anything new with your midwife at your next appointment.

The OGTT test

When offered

24 to 28 weeks if a risk factor is present. Earlier, at 16 to 18 weeks, if you had gestational diabetes in a previous pregnancy, then again at 24 to 28 weeks.

Time at hospital

Around 2.5 hours in total.

How the OGTT works

  1. Fast overnight

    No food for 8 to 10 hours. Water is usually allowed, check with your unit.

  2. Morning blood test

    On arrival at hospital, a fasting blood glucose level is taken.

  3. Drink the glucose solution

    75g of glucose dissolved in water, taken within 5 minutes.

  4. Rest for 2 hours

    Sit quietly. Bring something to read. No strenuous activity or food.

  5. Second blood test

    Post-glucose blood test to see how your body handled the sugar load.

Diagnostic thresholds (WHO criteria used in the UK)

  • Fasting: 5.6 mmol/L or above = gestational diabetes
  • 2-hour: 7.8 mmol/L or above = gestational diabetes

Results are usually available the same day or the next working day. The OGTT and diagnostic thresholds are described in detail in the NHS guidance on gestational diabetes and NICE guideline NG3.

Managing gestational diabetes

Blood sugar monitoring

Your diabetes team will give you a home testing kit. Most people test 4 times daily: fasting (first thing in the morning) and 1 hour after each main meal. Typical targets are fasting below 5.3 mmol/L and 1 hour after a meal below 7.8 mmol/L. Your team will confirm the targets for your unit.

Diet changes

There is no single gestational diabetes diet. The aim is to balance carbohydrates across the day. Eat regular smaller meals, choose lower-GI carbohydrates (wholegrain bread, oats, lentils), reduce sugary drinks, sweets and refined white carbs, and pair carbs with protein to slow glucose release. Ask for an NHS dietitian referral. You do not have to cut out all carbohydrates.

Physical activity

Gentle activity after meals is one of the most effective ways to lower blood sugar. A 15 to 20 minute walk after eating can make a real difference. Swimming, pregnancy yoga and light strength work all help too. See our guide to exercise in pregnancy.

Read our exercise in pregnancy guide →

Medication

If diet and exercise alone are not keeping your blood sugar in range, usually after 1 to 2 weeks of monitoring, medication is added. Metformin tablets are often tried first and are safe in pregnancy. Insulin injections may be used if metformin is not enough, or if your blood sugar is very high from the start. Needing insulin is not a failure, it simply means your body needs extra support during pregnancy.

Gestational diabetes and your birth

  • More frequent monitoring in the third trimester, often every 2 weeks
  • Extra growth scans to check your baby's size (larger babies are common)
  • Birth usually recommended before 41 weeks
  • Induction is often offered between 38 and 40 weeks if you are on insulin or medication, or if your baby is measuring large
  • Caesarean section is more likely if your baby is very large
  • Continuous monitoring (CTG) during labour
  • Your baby's blood sugar checked after birth, with feeding within 30 minutes of birth to prevent low blood sugar

After birth

Gestational diabetes usually resolves immediately after birth. You will have a blood sugar check 1 to 2 days after birth to confirm levels have normalised. An OGTT is offered 6 to 13 weeks after birth to rule out ongoing type 2 diabetes.

After that, an annual blood test is recommended. Having had gestational diabetes increases your lifetime risk of type 2 diabetes by up to 50%. Lifestyle steps (balanced diet, regular exercise, maintaining a healthy weight) significantly reduce that risk, and the changes you have already made in pregnancy are a great foundation.

The emotional side

A gestational diabetes diagnosis can feel overwhelming and unexpected. Many women feel anxious, guilty, or worried they have done something wrong. None of that is true. Gestational diabetes is a hormonal effect of pregnancy that some people are simply more susceptible to.

Support is available from your diabetes team, midwife and the Diabetes UK helpline on 0345 123 2399. The Gestational Diabetes UK Facebook community is also a warm place to compare notes.

Related guides and tools

Pregnancy weight gain guide→ Exercise during pregnancy→ Pre-eclampsia (shared risk factors)→ Foods to avoid in pregnancy→

A note from our team

This guide reflects NHS UK and NICE guidance on gestational diabetes. Your diabetes team are the experts on your individual care, and every unit has slightly different protocols. Read more about us.

Frequently asked questions

Does gestational diabetes go away after birth?
Yes, for most people. Gestational diabetes is caused by pregnancy hormones, and blood sugar levels usually return to normal within a day or two of giving birth. You will have a blood test before leaving hospital, and another OGTT is offered 6 to 13 weeks after birth to check for type 2 diabetes.
Will my baby be born with diabetes?
No. Your baby does not inherit gestational diabetes. However, babies of mothers with gestational diabetes can have low blood sugar for the first 24 to 48 hours, which is why early feeding (within 30 minutes of birth) is important and why babies are monitored closely. Most babies need no treatment beyond regular feeds.
Do I have to inject insulin?
Not necessarily. Most people with gestational diabetes manage it with diet and exercise alone. If medication is needed, metformin tablets are usually tried first. Insulin is only added if diet, exercise and metformin are not enough, or if your blood sugar is very high from diagnosis. About 1 in 5 to 1 in 3 people with gestational diabetes end up needing insulin.
Can I still have a normal birth with gestational diabetes?
Yes, many people with gestational diabetes have a straightforward vaginal birth. However, delivery is usually recommended before 41 weeks, and induction may be offered from 38 to 40 weeks if you are on insulin or if your baby is measuring large. Continuous monitoring during labour and feeding your baby soon after birth are standard.
Is gestational diabetes my fault?
No. Gestational diabetes is caused by pregnancy hormones that block insulin from working properly. Some people are more susceptible due to genetics, ethnicity, weight or age. It is not caused by something you did or did not eat. Managing it well gives you and your baby the best outcome, and you are doing that by reading this guide.
What foods should I avoid with gestational diabetes?
Avoid sugary drinks (cola, squash, fruit juice in quantity), sweets, biscuits, cakes, pastries, white bread, sugary cereals and large portions of refined carbs like white rice and pasta. Focus instead on wholegrains, protein with every meal, plenty of vegetables, and unsweetened dairy. A dietitian can give you a personalised plan.
What is the OGTT test?
The Oral Glucose Tolerance Test is the diagnostic test for gestational diabetes. You fast overnight, have a fasting blood test, drink a glucose solution, rest for 2 hours, then have a second blood test. It takes about 2.5 hours at hospital in total. Results are usually available the same day or the next working day.