Failed Glucose Challenge Test in Pregnancy: What Happens Next?

A failed glucose challenge test in pregnancy means your blood sugar one hour after a sweet glucose drink was above the cut-off your care team uses. It is a screening signal, not a diagnosis. The usual next step is a longer, fasting oral glucose tolerance test (OGTT), which is the test used to confirm or rule out gestational diabetes.

Cleveland Clinic states plainly that a higher-than-normal result after 60 minutes does not mean you have gestational diabetes, and that it is possible to fail the screening test but pass the glucose tolerance test. This guide explains the difference between the two tests and helps you prepare questions. It cannot interpret your result or predict what the next test will show.

A screening result is not an emergency, but some pregnancy symptoms are. Do not wait for your follow-up glucose test if you notice any of the following. The NHS advises contacting your maternity unit straight away (or local urgent services if you cannot reach them) for possible pre-eclampsia symptoms, and calling your midwife or maternity unit immediately about changes in your baby's movements, even in the middle of the night.

• Your baby moving less than usual, or a change in the usual pattern of movements later in pregnancy.
• A severe headache that does not go away with simple painkillers.
• Vision problems such as blurred vision or flashing lights.
• Pain below the ribs, or heartburn that does not settle with heartburn medicines.
• Sudden swelling of the face, hands or feet, being sick, or feeling very unwell.
• Any heavy bleeding, severe pain or fainting: seek emergency care through local services.

The glucose challenge test is the first step in what is often called a two-step approach. According to NIDDK and Cleveland Clinic, you do not need to fast. You drink a glucose solution and have blood taken one hour later. It is usually done between 24 and 28 weeks of pregnancy, or earlier for people at higher risk.

The diagnostic test is different. For the three-hour OGTT, Cleveland Clinic describes fasting beforehand, a fasting blood sample, a stronger glucose drink, and further blood samples at one, two and three hours. You usually need to stay at the clinic for the whole test.

Not every health system uses the same pathway. NIDDK notes that some clinicians go straight to an OGTT without a screening test first. In the UK, the NHS offers a two-hour OGTT at 24 to 28 weeks to people with risk factors, rather than a one-hour screen. If you have moved between countries or clinics, ask which test your current team uses.

Cut-offs vary. NIDDK says a result of 140 mg/dL or more means you may need to return for a fasting OGTT. Cleveland Clinic notes that some providers use 135 mg/dL instead. Results may also be reported in mmol/L in some countries, so check the unit printed on your report.

NIDDK also notes that a very high screening result, 200 mg/dL or more, may indicate type 2 diabetes. If your result is in that range, ask your care team directly how they are interpreting it and whether the plan differs from the usual follow-up test.

Cleveland Clinic mentions that eating a lot of sugary food shortly before the screen may affect the result. This is one reason a screening result needs a confirmatory test rather than a decision based on one number.

On the three-hour OGTT, each blood sample is compared with a threshold. NIDDK says gestational diabetes is indicated when glucose is high at two or more of the test times. Cleveland Clinic adds that if only one value is raised, some providers repeat the test a few weeks later. Thresholds differ between guidelines and laboratories, so rely on your own report and your care team's reading of it.

Your clinician may give you instructions for the days before the test, such as fasting times or how much carbohydrate to eat. Follow the instructions from your own clinic rather than general advice online. Some people feel nauseated or dizzy after the drink; tell the staff if you feel unwell during the test.

If the diagnostic test does show gestational diabetes, it is a common and manageable condition. The CDC notes that managing it can help make sure you have a healthy pregnancy and a healthy baby, and that there is a lot you can do. Your team will explain monitoring, eating and activity advice, and whether any medicine is needed.

Gestational diabetes often causes no symptoms, which is why screening exists. If your follow-up test is normal, ask whether any further checks are planned later in pregnancy. If you have had gestational diabetes, the CDC and NHS both advise ongoing blood sugar checks after birth because the risk of type 2 diabetes is higher.

Write the answers down and keep your printed result with them.

• What was my one-hour result, in what unit, and what cut-off does this clinic use?
• Is this a screening result only, and which diagnostic test is next?
• When is the follow-up test booked, and how should I prepare for it?
• How many values need to be high on the follow-up test for a diagnosis here?
• If one value is high, would the test be repeated, and when?
• If gestational diabetes is confirmed, who will support me with monitoring and next steps?
• Which symptoms should make me contact the maternity unit before my next appointment?

On SameCase, patients and verified doctors share de-identified cases. Reading how others moved from a failed screen to a follow-up test can help you notice questions you had not thought to ask, such as how preparation instructions differed or how results were explained. Other people's results cannot predict yours. We encourage you to take any questions back to your own midwife or doctor, who can see your full record.