How is gestational diabetes diagnosed?

Since any woman might develop gestational diabetes during pregnancy, all pregnant women, whether they fall into a high risk group or not, are typically screened for gestational diabetes.

This usually occurs between 24 and 28 weeks of pregnancy, when the hormones that cause gestational diabetes are at high levels. No preparations are required for this screening test.

Screening for gestational diabetes

The typical steps for the screening test at your health care provider's office are:

• You drink a 50-gram glucose beverage.
• You sit quietly for an hour.
• Your blood glucose level is measured. A result over 140 is considered a positive glucose screen.

After a positive result, you may be given a three-hour glucose tolerance test on another day to confirm or withdraw the diagnosis.

Diagnosing gestational diabetes

The typical steps to diagnose gestational diabetes using the glucose tolerance test are:

Glucose tolerance test

A blood glucose test measures the amount of sugar (glucose) in a sample of your blood.

Learn more about glucose tolerance tests in our health encyclopedia.

1. You fast the night before the test. On the days before the test, you should eat normally.
2. Your fasting blood glucose is measured before the test begins.
3. You drink a 100-gram glucose beverage at your health care provider’s office or lab.
4. You sit quietly for three hours.
5. Your blood glucose is measured at the one-, two-, and three-hour time spans during the three-hour period.
6. Two or more elevated test results means you have gestational diabetes.

Your health care provider will review your test results and tell you what happens next. Information covered may include:

• a special meal plan
• blood glucose monitoring
• urine testing for ketones
• exercise guidelines
• insulin therapy.

Your health care provider's clinic may have a diabetes dietitian or educator help you, or you may be referred to a diabetes center at your hospital.