Key points
- Confirm the exact test and preparation with Davie ObGyn or your laboratory before the appointment.
Why we check blood sugar
Pregnancy can make insulin less effective, allowing blood sugar to rise. Gestational diabetes often causes no symptoms, so testing is usually offered at 24 to 28 weeks. Some patients need earlier testing based on their history. NIDDK testing guidance
Know which test you are having
| Test | What to expect | Preparation |
|---|---|---|
| One-hour glucose challenge screen | A 50-gram glucose drink, then a blood draw one hour later | Fasting is generally not required; follow your lab's instructions |
| Three-hour glucose tolerance test | A fasting sample, a 100-gram drink, and samples over three hours | Fast as directed, usually at least eight hours; confirm water and medication instructions |
| Two-hour glucose tolerance test | A fasting sample, a 75-gram drink, and additional samples over two hours | Used by some practices; follow the specific fasting instructions |
An elevated one-hour screen usually means a diagnostic test is needed. It does not automatically confirm gestational diabetes. The two-hour and three-hour tests use different diagnostic rules. NIDDK overview
Make the visit easier
Eat your usual diet in the days before testing; do not cut carbohydrates to try to “pass.” Ask how long to allow, what you may drink, and which medicines to take. Bring a snack for after a fasting test. Tell the team beforehand if you have had bariatric surgery or have trouble tolerating sweet drinks.
The drink may cause nausea, lightheadedness, or an upset stomach. Blood draws may bruise. If you vomit or feel unwell, tell staff; you may need another plan or a repeat test. MedlinePlus glucose testing information
Questions about your pregnancy? Contact Davie ObGyn in Davie, Florida, at 954-880-1010. New and established patients are welcome. This information supports your prenatal care and does not replace an individual medical assessment. For urgent symptoms, call your care team promptly; for an emergency, call 911. Do not use a routine online message for urgent symptoms.
Medically reviewed by Rahil Malik, MD, FACOG, board-certified obstetrician-gynecologist. Last reviewed: September 26, 2026. This page is general information and does not replace a visit with your doctor.