The most common glucose tolerance test is the oral glucose tolerance test (OGTT).  You are not to eat or drink anything, besides water, after midnight prior to the test.  For the 1 hour glucose tolerance test, you will need to drink a liquid containing a concentrate of glucose.  Your blood is taken to test your sugar level 1 hour after you’ve drunk the glucose solution.  It’s important to drink the full 50 gram solution under 5 minutes to get accurate gestational diabetes testing results.  You are not to eat during the test.

The oral tolerance test is used to screen pregnant women for gestational diabetes,a temporary form of hyperglycemia, between weeks 24 and 28.   You  may be tested earlier in cases where gestational diabetes is suspected due to high risks for gestational diabetes due to health or family history.

If you have gestational diabetes, your doctor will usually order glucose levels throughout the rest of your pregnancy and after delivery to monitor your condition.

Gestational Diabetes Screening: Glucose Tolerance Test

More Information About Gestational Diabetes
What To Eat Before Gestational Diabetes Test – Gestational Diabetes Test
3 Hour Glucose Tolerance Test – What Is Gestational Diabetes?

It’s not uncommon to fail the one hour glucose tolerance test and go on to pass the 3 hour test.

The 1 hour glucose test requires you to drink 50 grams of a highly concentrated glucose solution to be read at the 1-hour mark.

The 3 hour glucose test requires you to drink 100 grams.  To prepare for the test, three days beforehand eat a diet that contains at least 150 grams of carbohydrates a day.  About 10 to 14 hours before the test, you do not eat or drink anything except for water.

Schedule the test for early in the morning.  The first sample of blood is drawn to take a baseline reading.  Next you will drink a glucose solution that contains 100 grams of glucose.  Many women get nauseated drinking the solution, but you must drink it quickly for the test results to be accurate.  If you throw up any of the solution, you will need to come back a different day to take the glucose tolerance test.

How do you know if you’ve failed the 3 hour test?

If two or more of your blood sugar levels are higher than the diagnostic blood glucose values, you have gestational diabetes.  Once you’ve been diagnosed with gestational diabetes, your doctor will develop a plan with your dietitian.

Normal Results -

• 100mg at 3 hours

Positive Results -

• Fasting – 105mg
• 1 hour – 190mg
• 2 hours – 165mg
• 3 hours – 145mg

Occasionally, if the mother fails one of the above tests in the 3 hour, the doctor may request you repeat the 3 hour glucose tolerance test.

More Information About Gestational Diabetes
What To Eat Before Gestational Diabetes Test – Gestational Diabetes Testing
What To Eat Before Gestational Diabetes Test – Causes of Gestational Diabetes

How is Gestational Diabetes Diagnosed?

Women at high risk for gestational diabetes should be screened as early as possible during their pregnancies before the 24th and 28th week of pregnancy, as other women would be tested.

To screen for gestational diabetes, you will need to take a test called the oral glucose tolerance test.  The test involves drinking a sweetened liquid (usually has to be drank under 5 minutes) which contains 50g of sugar.  The body absorbs the sugar rapidly causing blood sugar to spike within 30 to 60 minutes.  A blood sample is withdrawn from a vein in  your arm 1 hour after drinking the glucose solution.  The blood test will measure how the sugar solution was metabolized by the body.

A blood sugar level greater than or equal to 140mg/dL is seen as abnormal.  Another test will be ordered after you’ve fasted for several hours which will occur over a 3 hour period.

In women at high risk of developing gestational diabetes, a normal screening test is followed with another screening at 24 to 28 weeks for confirmation on the diagnosis.

Recommended Reading:

• Gestational Diabetes Diet Plan
• Managing Gestational Diabetes
• Blood Sugar Levels and Gestational Diabetes
• Risks with Gestational Diabetes

More Information About Gestational Diabetes
Gestational Diabetes Diet – Gestational Diabetes Testing
What To Eat Before Gestational Diabetes Test – Causes of Gestational Diabetes

You are not required to fast prior to the 1 hour glucose tolerance test but after you’ve drunk the glucose solution you won’t be able to eat or drink anything till your blood is taken. There are women who say that eating before taking the test has usually made them fail and some women have said they did not have anything to eat and still failed the first test but go on to pass the 2nd, 3 hour glucose tolerance test. Typically it’s not recommended to eat anything 2 to 3 hours before the test and anything very high in sugar. If you must eat, choosing something high in protein is recommended.

See:
Gestational Diabetes Testing
1 Hour Glucose Test
3 Hour Glucose Tolerance Test

The 3 hour glucose tolerance test requires that you fast for 12 to 14 hours earlier since the test starts with a “fasting base glucose” to compare the rest of the blood draws after you have drunk the glucose solution. You won’t be able to eat anything between blood draws for this test which is taken every hour, 3 more times.

More Information About Gestational Diabetes
Gestational Diabetes Diet – Gestational Diabetes and Blood Sugar Levels
Carb Counting and Gestational Diabetes – Gestational Diabetes After the Baby