A passing result on the 1-hour glucose test is a blood sugar level below 130 or 140 mg/dL, depending on the cutoff your provider uses. This screening test, done during pregnancy to check for gestational diabetes, is one of the most common prenatal lab tests. If your result falls below the cutoff, no further testing is needed.
The Two Passing Cutoffs
There isn’t one universal number that counts as “passing.” The American College of Obstetricians and Gynecologists (ACOG) recommends a cutoff of either 130 mg/dL or 140 mg/dL, and individual practices choose which one to use. A 130 mg/dL cutoff catches more cases of gestational diabetes but also flags more women who don’t actually have it, leading to more follow-up testing. A 140 mg/dL cutoff is less sensitive but produces fewer false positives.
Your provider’s office will tell you which threshold they use. If your blood sugar comes back at, say, 125 mg/dL, you pass under either cutoff. A result of 135 mg/dL would pass at a practice using 140 but fail at one using 130. This is why two women with the same result can get different answers.
How the Test Works
The 1-hour glucose test (sometimes called the glucose challenge test or GCT) is a screening, not a diagnosis. You drink a solution containing 50 grams of glucose, which tastes like a very sweet flat soda. Then you wait one hour and have your blood drawn. That single blood draw measures how efficiently your body processed the sugar.
You do not need to fast before this test. You can eat normally beforehand, though some providers suggest avoiding a heavy sugary meal right before, since that could push your numbers higher. Once you drink the glucose solution, you should not eat or drink anything else until the blood draw is complete.
When the Test Happens
Most pregnant women are screened between 24 and 28 weeks of pregnancy. This is when pregnancy hormones from the placenta are most likely to interfere with how your body uses insulin, making gestational diabetes detectable.
If you have risk factors for diabetes, such as a history of gestational diabetes in a previous pregnancy, a family history of type 2 diabetes, a BMI over 30, or being over age 35, your provider may screen you earlier in pregnancy, sometimes at your very first prenatal visit. If that early screen is normal, you’ll typically be tested again at 24 to 28 weeks.
What Happens If You Don’t Pass
Failing the 1-hour screen does not mean you have gestational diabetes. It means your blood sugar was high enough to warrant a more thorough test. The majority of women who fail the 1-hour screening go on to pass the follow-up test.
The follow-up is a 3-hour glucose tolerance test, and it requires fasting overnight. Your blood is drawn four times: once fasting, then at one, two, and three hours after drinking a larger glucose solution (100 grams). The target values for this test are:
- Fasting: 95 mg/dL or lower
- 1 hour: 180 mg/dL or lower
- 2 hours: 155 mg/dL or lower
- 3 hours: 140 mg/dL or lower
You need two or more of those four values to be above the threshold to receive a gestational diabetes diagnosis. If only one value is elevated, you typically pass, though your provider may recommend dietary changes or closer monitoring.
Common Side Effects of the Drink
Most women tolerate the glucose drink without problems. The most common complaints are nausea, feeling sweaty, or lightheadedness after drinking the solution. These symptoms are temporary and usually resolve within an hour or two. Serious side effects are very uncommon. Eating a small meal with protein before the test (since fasting isn’t required) can help reduce nausea for some women.
What Your Number Actually Tells You
If you pass, your body is handling blood sugar well at this stage of pregnancy, and you won’t need additional glucose testing unless new concerns arise. If your result is just barely over the cutoff, try not to read too much into it. The 1-hour test is intentionally designed to cast a wide net. It’s a screening tool, not a final answer, and a slightly elevated result often leads to a perfectly normal 3-hour test.
If your result is significantly elevated, say 200 mg/dL or higher, some providers will skip the 3-hour test entirely and diagnose gestational diabetes based on that single value, since a number that high strongly suggests the diagnosis. Your provider will walk you through next steps, which for most women involve dietary adjustments and blood sugar monitoring rather than anything more intensive.