You passed your glucose test if your blood sugar fell below the cutoff your provider’s office uses, which is typically 140 mg/dL for the standard one-hour screening done during pregnancy. Some clinics set the bar lower at 130 mg/dL, so the specific threshold depends on where you were tested. If you’re waiting on results or trying to make sense of a lab report you’ve already received, here’s how to read the numbers for every common version of the test.
The One-Hour Glucose Screening
This is the test most pregnant people take between weeks 24 and 28. You drink a sugary solution containing 50 grams of glucose, then have your blood drawn one hour later. No fasting is required beforehand.
A result below 140 mg/dL (7.8 mmol/L) is considered normal, and that means you passed. However, some clinics and labs use a stricter cutoff of 130 mg/dL (7.2 mmol/L). Your lab report will list a “reference range,” which is the window of values that lab considers normal. If your number falls within that range, you’ll typically see it marked as normal. If it falls outside the range, the result may be flagged as abnormal or high.
A result above your clinic’s cutoff does not mean you have gestational diabetes. It means you need a longer, more detailed follow-up test. The one-hour screening is designed to cast a wide net, and many people who “fail” it turn out to be fine. The actual rate of gestational diabetes is somewhere between 2 and 10 percent of pregnancies.
The Three-Hour Diagnostic Test
If your one-hour result came back high, your provider will schedule a three-hour glucose tolerance test. This one requires fasting for at least eight hours. Your blood is drawn four times: once fasting, then at the one-hour, two-hour, and three-hour marks after drinking a 100-gram glucose solution.
The most widely used set of thresholds, known as the Carpenter-Coustan criteria, are:
- Fasting: below 95 mg/dL
- One hour: below 180 mg/dL
- Two hours: below 155 mg/dL
- Three hours: below 140 mg/dL
Some providers use a slightly more lenient set of numbers (105, 190, 165, and 145 mg/dL at those same intervals). Your lab report will specify which set of cutoffs it’s using in its reference ranges.
To pass, you generally need all four blood draws to come in below the thresholds. A diagnosis of gestational diabetes typically requires two or more values that meet or exceed the cutoffs, though some clinicians will flag a single elevated value for closer monitoring. If only one reading is borderline high and the rest are normal, that’s a conversation worth having with your provider, but it’s a very different situation from multiple elevated numbers.
The One-Step 75-Gram Test
Some clinics skip the one-hour screening entirely and go straight to a single two-hour test using 75 grams of glucose. This approach is more common outside the United States and follows international guidelines. Blood is drawn at fasting, one hour, and two hours.
The cutoffs for this version are:
- Fasting: below 92 mg/dL
- One hour: below 180 mg/dL
- Two hours: below 153 mg/dL
Unlike the three-hour test, a single elevated value on the 75-gram test is enough for a gestational diabetes diagnosis. The thresholds are lower, so this version catches more cases.
Fasting Glucose Tests Outside Pregnancy
If you’re not pregnant, the glucose test you took was likely a fasting plasma glucose test, which checks your blood sugar after at least eight hours without food or drink (other than water). The ranges here are straightforward:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
A result in the prediabetes range doesn’t mean you’ll develop diabetes, but it does signal that your body is having a harder time managing blood sugar than it should. A result of 126 mg/dL or above will usually prompt your provider to repeat the test or order additional bloodwork before making a formal diagnosis.
How to Read Your Lab Report
Most lab reports include your result, the reference range, and a flag if your number falls outside that range. The reference range is the set of values considered normal for healthy people at that lab. Words like “within normal limits” or simply “normal” mean you passed. A result flagged as “high” or “abnormal” means your number exceeded the reference range.
Keep in mind that reference ranges can vary slightly between labs. A value of 138 mg/dL on a one-hour screening would be normal at a lab using 140 mg/dL as the cutoff but abnormal at one using 130 mg/dL. If your result is close to the line and you’re not sure which threshold your clinic follows, that’s worth asking about directly.
When Results Come Back
Most glucose test results are available within a few business days, though the exact turnaround time varies by lab. Many providers now release results through online patient portals, so you may see your numbers before anyone calls you. If you see a flagged result in your portal, it can feel alarming, but remember that a high one-hour screening is a common first step, not a diagnosis. Most people who fail the initial screening go on to pass the three-hour test.
If your results are normal across the board, you typically won’t need any follow-up glucose testing during that pregnancy. If you were tested outside of pregnancy and your numbers are in the prediabetes range, your provider will likely recommend retesting in one to three years along with lifestyle changes that can bring those numbers back down.