Pregnancy screening
When is the glucose test for gestational diabetes?
Gestational diabetes is diabetes that develops during pregnancy. The US Preventive Services Task Force recommends one screening test at 24 weeks or later. Enter how far along you are to see where you stand.
Your pregnancy
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What you will see
Whether your glucose test is still ahead, due now or overdue, by the USPSTF advice.
Educational only, not medical advice. Your clinician decides when and how you are tested.
Source
US Preventive Services Task Force, August 2021 recommendation on screening for gestational diabetes.
Validated in
Pregnant people who have not been diagnosed with type 1 or type 2 diabetes before.
Limits
It does not diagnose gestational diabetes or read glucose results. Risk factors do not change the routine timing; they are a reason to ask your clinician about an earlier test.
What the USPSTF recommends
| When | Recommendation | Grade |
|---|---|---|
| 24 weeks of pregnancy or later | Screen for gestational diabetes | B |
| Before 24 weeks | Evidence insufficient to weigh benefits and harms | I |
The USPSTF concludes with moderate certainty that screening at 24 weeks or later has a moderate net benefit for mothers and babies (USPSTF 2021). Screening is done once. In the US it usually happens before 28 weeks, and people who start prenatal care after 28 weeks should be screened as soon as possible (USPSTF 2021). The American College of Obstetricians and Gynecologists recommends testing between 24 and 28 weeks, as cited by the USPSTF (USPSTF 2021).
Why it matters
Gestational diabetes affects an estimated 5.8% to 9.2% of pregnancies in the US, and possibly more under broader criteria (USPSTF 2021). It raises the risk of preeclampsia, a very large baby (which can cause shoulder dystocia and birth injury) and low blood sugar in the newborn (USPSTF 2021). People who had it are also at higher risk of type 2 diabetes after pregnancy (USPSTF 2021).
How the test works
Most US practices use two steps. First a 50-gram glucose drink with a blood test, done between 24 and 28 weeks without fasting. If that result is at or above the cutoff, a longer glucose tolerance test follows: a fasting blood sample, a 75- or 100-gram glucose drink, then blood tests after 1, 2 and often 3 hours. Two or more values at or above the cutoffs mean gestational diabetes (USPSTF 2021).
The one-step approach skips the screening drink: everyone has a fasting sample, a 75-gram drink and tests after 1 and 2 hours, and one value at or above the cutoff is enough for the diagnosis (USPSTF 2021).
Who is at higher risk
Risk is higher with obesity, older maternal age, gestational diabetes in a past pregnancy, a family history of diabetes, and Hispanic, Native American, South or East Asian, or Pacific Island descent (USPSTF 2021). The USPSTF notes that differences between racial and ethnic groups may partly reflect social factors such as lower socioeconomic status or structural racism (USPSTF 2021). Some people with risk factors for type 2 diabetes are tested in early pregnancy; that is left to the clinician's judgment (USPSTF 2021).
If the test is positive
Treatment usually starts with moderate physical activity, changes to diet, support from diabetes educators and nutritionists, and checking blood sugar. If blood sugar stays high, medicine such as insulin may be added, along with closer monitoring (USPSTF 2021).
Common questions
Can screening cause harm?
Studies found no rise in anxiety or depression from screening or from a false-positive result, and a small, short-lived rise in anxiety after a diagnosis (USPSTF 2021).
I already have type 2 diabetes. Does this apply?
No. The recommendation is for people not previously diagnosed with type 1 or type 2 diabetes (USPSTF 2021).
Also see the preeclampsia risk check, the blood pressure in pregnancy check, the pregnancy weight gain calculator, the A1C to average glucose converter, prediabetes and the BMI calculator.
Sources
- US Preventive Services Task Force. Screening for Gestational Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(6):531. www.uspreventiveservicestaskforce.org/uspstf/recommendation/gestational-diabetes-screening
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-10-29. Spotted an error? See About.