Glucose Screen for Gestational Diabetes

Medically reviewed by Drugs.com. Last updated on Jun 2, 2025.

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AMBULATORY CARE:

A glucose screen for gestational diabetes

is a blood test to find out if you have diabetes caused by pregnancy. The test measures the level of glucose (sugar) in your blood at different points in time.

Why you need a glucose screen:

High blood glucose levels throughout your pregnancy can be harmful to you and to your unborn baby. You will need to manage your blood glucose if you do have gestational diabetes. Healthcare providers will help you create meal and physical activity plans to keep your blood glucose levels stable.

When the glucose screen is done:

The test may be done at or after 24 weeks of pregnancy. You may be tested during your first prenatal visit or before 15 weeks of pregnancy if you have an increased risk for diabetes. Your risk is increased if you have a family member with diabetes. You also have an increased risk if you have prediabetes, overweight, or obesity. Your risk for gestational diabetes is also higher if you have given birth to a large baby before.

Related medications

How the 1-step glucose screen is done:

• You will fast for as many hours as your healthcare provider directs.
• A sample of blood will be taken from a vein in your arm. It will be checked for the amount of glucose it contains.
• Your healthcare provider will then give you a glucose drink.
• Your blood will be tested again 1 hour and 2 hours after you finish the glucose drink. During this time, you cannot eat or drink anything other than water.
• Your healthcare provider will review your test results to see how your blood glucose level changed over time.
• You may need the test again 4 to 12 weeks after your baby is born. The test will check that your blood sugar levels returned to normal. You may continue to be checked for diabetes every 3 years.

How the 2-step glucose screen is done:

• First step: You do not have to fast. You will be given a glucose drink. Your blood will be tested 1 hour after you finish the glucose drink. During this time, you cannot eat or drink anything other than water. If your blood glucose is higher than a certain level, another test will be ordered.
• Second step:
  • You will fast for as many hours as your healthcare provider directs.
  • A sample of blood will be taken from a vein in your arm. It will be checked for the amount of glucose it contains.
  • Your healthcare provider will then give you a glucose drink.
  • Your blood will be tested again 1 hour, 2 hours, and 3 hours after you finish the glucose drink. During this time, you cannot eat or drink anything other than water.
  • Your healthcare provider will review your test results to see how your blood glucose level changed over time.

Follow up with your doctor or diabetes care team as directed:

Write down your questions so you remember to ask them during your visits.

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