Glucose Test

Between weeks 24-28, everyone gets screened for gestational diabetes (GD). The test checks how your body handles sugar during pregnancy. GD affects about 5-9% of U.S. pregnancies, and rates have been rising — up 36% between 2016 and 2024.

GD often has no symptoms, which is why screening is routine. Most people who are diagnosed manage it with dietary changes alone, and it resolves after delivery.

How the Test Works

Most providers in the U.S. use a two-step approach:

Step 1: The 1-hour glucose challenge (screening)

• You drink a sugary liquid (glucola) containing 50g of glucose
• Blood is drawn 1 hour later
• You don't need to fast beforehand
• If your blood sugar is below the cutoff (usually 130-140 mg/dL, depending on your provider), you're done

Step 2: The 3-hour glucose tolerance test (diagnostic)

• Only if step 1 comes back high — which happens in about 15-25% of people screened
• You fast for 8-14 hours beforehand
• Blood is drawn fasting, then at 1, 2, and 3 hours after drinking a 100g glucose solution
• GD is diagnosed if 2 or more values are elevated

Practical Tips for the Test

• 1-hour test: You can eat normally beforehand, but some providers suggest avoiding very sugary foods the morning of to reduce false positives
• 3-hour test: You'll need to fast, so schedule it first thing in the morning. Bring snacks and water for after
• The glucose drink is very sweet — some people find it easier to drink cold and quickly
• Some people feel nauseous, lightheaded, or shaky during the test. This is common and temporary
• You'll be sitting in the office for a while (especially the 3-hour). Bring something to do

Who Gets Screened Early?

If you have risk factors, your provider may screen you in the first trimester (before 24 weeks). Risk factors include:

• BMI of 25 or higher (23 for Asian Americans)
• Previous GD
• Previous baby weighing 9+ pounds
• Family history of type 2 diabetes
• PCOS
• Being physically inactive

A negative early screen doesn't get you out of the 24-28 week test — you'll still be screened again.

If You're Diagnosed

A GD diagnosis can feel scary, but it's very manageable. Here's what typically happens:

Diet and lifestyle changes (first line)

• You'll work with your provider or a dietitian to adjust your meals — focusing on balancing carbs with protein and fat, and spreading intake across the day
• Regular physical activity (30 minutes of moderate exercise on most days) helps with blood sugar control
• You'll monitor blood sugar at home with a glucose meter, typically checking fasting levels and 1-2 hours after meals

Blood sugar targets:

• Fasting: below 95 mg/dL
• 1 hour after meals: below 140 mg/dL
• 2 hours after meals: below 120 mg/dL

If diet isn't enough

• About 15-30% of people with GD need medication to manage blood sugar
• Insulin is the recommended medication because it doesn't cross the placenta
• Some providers use metformin as an alternative, though it does cross the placenta
• Needing medication is not a failure — some people's placentas just produce more insulin-resistant hormones

Risks in Context

Unmanaged GD increases the chance of:

• Larger baby (macrosomia) — which can complicate delivery and increase C-section likelihood
• Low blood sugar in the newborn after birth
• Preeclampsia in the pregnant person
• Preterm birth

With proper management, these risks drop significantly. Most people with GD have healthy pregnancies and healthy babies.

After Delivery

GD usually resolves after birth. Your provider will test your blood sugar 6-12 weeks postpartum to confirm.

The long-term picture: about 50% of people with GD develop type 2 diabetes later in life. Early interventions (maintaining a healthy weight, staying active, eating well) can reduce that progression risk by 35-40%.