Failed the 1-hour glucose test? What happens next
A high 1-hour result is a screen, not a diagnosis. The next step is a longer glucose tolerance test, and about 2 out of 3 people who take it do not have gestational diabetes. For that test you fast first, drink a stronger glucose drink, and give blood several times over 3 hours.
The two tests
| 1-hour screen | 3-hour glucose tolerance test | |
|---|---|---|
| Fasting before | Not needed | Nothing but sips of water for 8 to 14 hours |
| The drink | A glucose drink | A drink with 100 grams of glucose |
| Blood draws | One, 1 hour after the drink | Before the drink, then every hour for 3 hours |
| Time | About 1 hour | At least 3 hours, with no eating during the test |
Most of the time, a 1-hour result of 140 mg/dL (7.8 mmol/L) or less is normal. Above that, the next step is the longer test, and most people who take it, about 2 out of 3, do not have gestational diabetes.1 Some clinics skip the screen and use one 2-hour test with 75 grams of glucose instead.1
The cut-off values
| Blood draw | 3-hour test (100 g): high if | 2-hour test (75 g): high if |
|---|---|---|
| Fasting | 95 mg/dL (5.3 mmol/L) or more | 92 mg/dL (5.1 mmol/L) or more |
| 1 hour | 180 mg/dL (10.0 mmol/L) or more | 180 mg/dL (10.0 mmol/L) or more |
| 2 hours | 155 mg/dL (8.6 mmol/L) or more | 153 mg/dL (8.5 mmol/L) or more |
| 3 hours | 140 mg/dL (7.8 mmol/L) or more | (no 3-hour draw) |
Values from MedlinePlus.1 These are test cut-offs, not the targets you aim for each day after a diagnosis. The daily targets are different: see blood sugar targets.
How to prepare
- Eat your normal food in the days before the test, and ask your provider if any of your medicines can change the result.1
- For the long test, nothing but sips of water for 8 to 14 hours before, and no food during it.1 A morning appointment keeps the fast short.
- The drink tastes like a very sweet soda. Some people feel sick, sweaty or lightheaded afterwards; serious side effects are very uncommon.1 Bring something to do and something to eat for after.
When the tests happen
Most people are tested between 24 and 28 weeks of pregnancy. If you have risk factors, your blood sugar is tested earlier.2
After the result
- One high value: your provider may suggest some changes to what you eat, and test you again later.1
- More high values: your provider tells you whether it means gestational diabetes for the test you had. With a diagnosis, you have more prenatal visits and you check and record your blood sugar.2 First Fork times each check after a meal from the first bite, so the reading is taken at the time your clinic asked for.
Next: just diagnosed: the first week.
Questions
Does failing the 1-hour glucose test mean I have gestational diabetes?
No. It is a screen. About 2 out of 3 people who go on to the longer test do not have gestational diabetes.
What is a normal 1-hour glucose test result?
Most of the time, 140 mg/dL (7.8 mmol/L) or less.
Do I need to fast for the 1-hour test?
No. You fast for 8 to 14 hours before the longer 3-hour or 2-hour test.
What if only one number is high on the 3-hour test?
Your provider may suggest some food changes and test you again later.
Sources
- MedlinePlus (US National Library of Medicine). Glucose screening tests during pregnancy. https://medlineplus.gov/ency/article/007562.htm
- ACOG. Gestational Diabetes (FAQ 177, reviewed April 2026). https://www.acog.org/womens-health/faqs/gestational-diabetes
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