GUIDE
The glucose screening test at 24-28 weeks checks for gestational diabetes. You drink a sugary solution and have blood drawn one hour later.
Gestational diabetes affects 6 to 9 percent of pregnancies. The one-hour test is a screening — about 15 to 25 percent of people fail it and move on to the three-hour diagnostic test. Failing the one-hour does not mean you have gestational diabetes.
Be prepared from day one
Gestational diabetes develops when your body cannot produce enough insulin to handle the increased blood sugar demands of pregnancy. The placenta produces hormones that make your cells more resistant to insulin, and for some people, the pancreas cannot keep up.
Unmanaged gestational diabetes can lead to a larger-than-average baby (macrosomia), which increases the risk of delivery complications. It can also cause low blood sugar in the baby after birth and increases the risk of preeclampsia. The good news: when detected and managed, outcomes are excellent.
The glucose screening test is a standard part of your prenatal visit schedule, recommended by ACOG for all pregnancies between 24 and 28 weeks. If you have risk factors, your provider may test you earlier in pregnancy as well.
The one-hour test is a screening, not a diagnosis. Many people who fail it do not have gestational diabetes.
The glucose solution (often called glucola) contains 50 grams of glucose for the one-hour test or 100 grams for the three-hour test. It comes in several flavors — orange, lemon-lime, and fruit punch are most common. It tastes like a very concentrated, flat soda.
You need to finish it within 5 minutes. Some tips: drink it cold (ask the lab to refrigerate it), use a straw, and do not sip slowly — steady drinking makes it easier. Some people feel nauseous, lightheaded, or jittery afterward — this is a normal response to a concentrated sugar load.
Some providers now offer alternatives such as jelly beans, specific candy servings, or a standardized breakfast. Ask your provider if alternatives are available at your practice.
| Test | Drink | Normal | Elevated |
|---|---|---|---|
| 1-hour screening | 50g drink | < 130 or < 140 mg/dL* | ≥ 130 or ≥ 140 mg/dL* |
| 3-hour fasting | Fasting draw | < 95 mg/dL | ≥ 95 mg/dL |
| 3-hour — 1 hour | 100g drink | < 180 mg/dL | ≥ 180 mg/dL |
| 3-hour — 2 hours | 100g drink | < 155 mg/dL | ≥ 155 mg/dL |
| 3-hour — 3 hours | 100g drink | < 140 mg/dL | ≥ 140 mg/dL |
You are diagnosed with gestational diabetes if 2 or more of the 4 blood draws are at or above the threshold values.
For the one-hour screening, a result below your provider's threshold (130 or 140 mg/dL) means you passed — no further testing is needed. A result at or above the threshold means you proceed to the three-hour test.
For the three-hour test, gestational diabetes is diagnosed if two or more of the four blood draws (fasting, 1-hour, 2-hour, 3-hour) are at or above the threshold values. If only one value is elevated, you do not meet the diagnostic criteria, though your provider may recommend dietary monitoring.
Having risk factors does not mean you will develop gestational diabetes. Many people with no risk factors are diagnosed, and many with multiple risk factors are not.
Gestational diabetes is manageable. Most people control it with diet modifications and blood sugar monitoring. You will check your blood sugar several times a day and learn which foods keep your levels stable. Your provider will adjust your care plan as needed and may increase monitoring in the third trimester.
Whether or not you are diagnosed with gestational diabetes, the glucose test is an important data point in your pregnancy care. Your provider uses it alongside other information from your blood work and anatomy scan to build a complete picture of your health.
If you are diagnosed, your care team will monitor you more closely in the third trimester, and you may have additional growth ultrasounds. Medication safety questions often come up — see our pregnancy-safe medications guide for a reference, and always discuss any supplements or changes with your provider.
For the full schedule of what tests happen when, see our prenatal visit schedule.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
