Prepare by eating an adequate carbohydrate diet for 3 days, then fast 8–14 hours (water allowed). At the lab, have a fasting blood draw, drink a 100 g glucose solution within 5 minutes, then get blood drawn at 1, 2 and 3 hours. Remain seated, avoid food, smoking and heavy activity during the 3‑hour test. Results are compared to standard thresholds.

A positive oral glucose tolerance test indicates impaired glucose metabolism or diabetes. Clinicians confirm the diagnosis, start regular blood‑glucose monitoring, and recommend dietary changes, exercise, and weight management. Medications (metformin or insulin) may be prescribed if needed. Pregnant patients receive intensified fetal and glucose monitoring to reduce complications. Long‑term follow‑up and repeat testing after pregnancy are advised.

The 100 g glucose test in pregnancy is a diagnostic 3-hour oral glucose tolerance test used to confirm gestational diabetes after an abnormal screening. After overnight fasting a baseline blood sample is taken, you drink a 100-gram glucose solution, and blood is drawn at 1, 2 and 3 hours to measure blood sugar. It identifies impaired glucose handling; mild nausea or dizziness can occur.

Whether 100 mg/dL is high in pregnancy depends on timing. A fasting plasma glucose of 100 mg/dL is mildly elevated—above many guideline cutoffs (commonly ~92–95 mg/dL)—and often prompts further testing (oral glucose tolerance test). A random or post‑meal reading of 100 mg/dL is generally normal. Discuss results with your clinician for definitive assessment and follow‑up.

Gestational diabetes can cause excess fetal growth (macrosomia), increasing risks of birth injury, complicated delivery (including shoulder dystocia), and emergency C‑section. Newborns may have low blood sugar (neonatal hypoglycemia), respiratory distress, jaundice, or require NICU care. Long-term, children face higher risk of obesity and type 2 diabetes. Poorly controlled maternal glucose also raises stillbirth risk.

Glucose tolerance test costs vary by country and facility. Public health services often cover it (for example, free in the UK). In India, private labs typically charge about ₹150–₹800. In the United States, out‑of‑pocket costs commonly run roughly $50–$200, and can be higher with facility or provider billing. Final price depends on test type, lab, and insurance coverage.