The 1-Hour Glucose Test: What to Expect

What is the 1-hour glucose test?

The 1-hour glucose challenge is a routine prenatal screen for gestational diabetes, usually offered between 24 and 28 weeks of pregnancy 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. According to the American College of Obstetricians and Gynecologists, you drink a measured 50-gram glucose solution, the sweet drink often called glucola, and have your blood drawn exactly one hour later 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. Fasting is not required for this first step, so you can eat normally beforehand.

The lab checks a single blood-sugar value against a screening cutoff, commonly 130 to 140 mg/dL depending on the practice 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. A number at or above that line does not diagnose anything; it simply flags who moves on to a longer confirmatory test. Roughly 1 in 5 people screen positive on this first pass 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. You can see what else happens at your prenatal visits.

Why do providers screen everyone?

Screening every pregnant person, rather than only those who seem high-risk, catches gestational diabetes that would otherwise go unnoticed. Blood sugar and pregnancy outcomes rise together on a continuous curve, with no single point where risk suddenly begins, as the landmark HAPO study of more than 23,000 pregnancies showed 2Ref 2HAPO Study Cooperative Research Group / Metzger BE, et al. (2008).Hyperglycemia and adverse pregnancy outcomes.The continuous relationship between maternal glucose and adverse outcomes across more than 23,000 pregnancies, with no clear threshold, and the association of higher glucose with type 2 diabetes risk later in life. Higher maternal glucose is linked to larger babies, delivery complications, and newborn low blood sugar, even below older diagnostic thresholds 2Ref 2HAPO Study Cooperative Research Group / Metzger BE, et al. (2008).Hyperglycemia and adverse pregnancy outcomes.The continuous relationship between maternal glucose and adverse outcomes across more than 23,000 pregnancies, with no clear threshold, and the association of higher glucose with type 2 diabetes risk later in life.

Treating the condition once found measurably lowers these risks, according to randomized trials 3Ref 3Crowther CA, Hiller JE, Moss JR, et al. / Australian Carbohydrate Intolerance Study in Pregnant Women (ACHOIS) (2005).Effect of treatment of gestational diabetes mellitus on pregnancy outcomes.Randomized-trial evidence that treating gestational diabetes once diagnosed measurably lowers the risk of adverse pregnancy outcomes. That is why guidelines recommend universal screening in the late second trimester 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. Gestational diabetes affects roughly 6 to 9 in 100 pregnancies, so a positive screen is common rather than rare 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. Our gestational diabetes guide covers day-to-day management.

What does the orange drink involve?

The orange drink is the part most people remember, and it is more manageable than its reputation. Most labs use a 50-gram glucose beverage that tastes like flat, very sweet soda; chilled or over ice, it goes down more easily 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. You have about five minutes to finish it, then wait one hour with no additional food or drink before the single blood draw 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent.

Some people feel briefly nauseated, shaky, or warm, sensations that overlap with ordinary pregnancy nausea and usually pass quickly. Bringing a book or your phone helps, since the wait is the longest part. The Office on Women's Health notes this screen is a standard piece of routine prenatal care 4Ref 4Office on Women's Health (U.S. HHS) (2025).Prenatal care.Glucose screening as a standard, routine component of prenatal care in the late second trimester. Eating balanced meals in the preceding days keeps the result reliable without any special preparation.

What does a high screening result mean?

A screening value above the cutoff means the test worked as designed, not that you have diabetes. Most people who screen positive on the 1-hour test go on to pass the longer diagnostic test and never receive a gestational diabetes diagnosis 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. Providers confirm with a 3-hour glucose tolerance test, where two or more abnormal values are needed to diagnose the condition 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. Risk factors such as a prior large baby, a family history of type 2 diabetes, or insulin resistance raise the odds, but many diagnosed people have none of them 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. A single elevated screen is a prompt for more information, not a verdict. Failing the screen while ultimately passing the diagnostic test happens often and reflects the screen's deliberately low threshold 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent.

When your glucose screen needs a closer look

Gestational diabetes screening results are best interpreted alongside your full pregnancy picture. A clinician can explain your practice's exact cutoff, walk you through the next step if your screen is positive, and tailor the plan to your history. That history matters, because gestational diabetes also signals higher lifetime risk of type 2 diabetes later, including through the perimenopausal years 2Ref 2HAPO Study Cooperative Research Group / Metzger BE, et al. (2008).Hyperglycemia and adverse pregnancy outcomes.The continuous relationship between maternal glucose and adverse outcomes across more than 23,000 pregnancies, with no clear threshold, and the association of higher glucose with type 2 diabetes risk later in life. In a teenage first pregnancy and in later pregnancies alike, the same 24-to-28-week timing applies, so the screen rarely changes by age 1Ref 1American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus.Timing of the 24-to-28-week screen, the 50-gram glucose challenge, screening cutoffs around 130 to 140 mg/dL, the two-step approach with a confirmatory 3-hour test, and gestational diabetes prevalence of roughly 6 to 9 percent. If you are newly expecting, you can schedule prenatal care to map out testing early. Gale can help you prepare questions for that visit so the screening step feels routine rather than worrying.