How Do I Interpret My Glucose Tolerance Test Results?

Cindy Quarters

The glucose tolerance test is a blood test that is used to check blood glucose levels in order to screen for either gestational or type 2 diabetes. The test involves a period of fasting, then ingesting a quantity of glucose. The blood glucose level is tested one or more times after the glucose is ingested. An individual’s results are compared to the expected numbers. If the glucose tolerance test results show a blood glucose level out of line with acceptable levels, it indicates the possibility of diabetes or other health problems.

Blood glucose levels can be tested using home kits.
Blood glucose levels can be tested using home kits.

To prepare for blood glucose testing, the patient should maintain a normal diet and daily schedule for a week or so before the test. He or she must then fast for at least eight hours immediately prior to the test. Tthe patient must also not have anything to drink during those eight hours.

A glucose blood test measures the amount of glucose or "sugar" in the blood.
A glucose blood test measures the amount of glucose or "sugar" in the blood.

How the test is administered depends on whether a person is being tested for type 2 diabetes or gestational diabetes. Testing for type 2 diabetes involves drawing blood once, two hours after the patient drinks a sugary drink containing a measured amount of glucose. When testing for gestational diabetes, which is the type of diabetes that can occur during pregnancy, blood is drawn at least once, and may be drawn several times over a period of hours after the glucose solution has been ingested.

In order to interpret the glucose tolerance test results, blood test results are compared to levels that are considered within normal rangel. Normal levels for a non-pregnant person are 140 mg/dL (milligrams per deciliter), and for a woman who is pregnant they run about 95 mg/dL. Two hours after drinking the solution, glucose tolerance test results should be under 200 mg/dL in the type 2 diabetes test and 155 mg/dL when screening for gestational diabetes. These values may differ somewhat with different doctors or laboratories, but are generally considered good average results.

When the glucose tolerance test results show numbers higher than the average, it may be an indicator of diabetes, requiring further diagnostic testing. Glucose tolerance test results may also be affected by illness, stress, or medication. These factors must also be taken into account when interpreting the test results, since they may lead to abnormal levels even though there is no medical problem present. Results above the normal levels may also indicate other illnesses besides diabetes, also requiring further diagnostic testing and a thorough review of the patient's history.

A oral glucose tolerance test (OGTT) requires the patient to fast for eight hours prior to the blood draw.
A oral glucose tolerance test (OGTT) requires the patient to fast for eight hours prior to the blood draw.

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Discussion Comments


@sunnySkys - I'm glad your cat is doing well on his medicine. Too bad the test was so expensive though!

A friend of mine was pregnant a little while ago (she actually just had the baby a few weeks ago) and I remember when she did this test. She was totally miserable going without food before heading to the doctor for the test.

She didn't have gestational diabetes though, so she considered the misery worth it!


They actually do a test like this on animals also. My cat has diabetes (poor kitty) and after he was diagnosed the doctor had me drop him off for a glucose tolerance test.

They kept him all day long and tested his glucose levels every hour or so. This way they could really pinpoint how much insulin kitty needed. The test must have been accurate, because he's doing very well on the insulin.

However, I hope he doesn't need another test like this anytime soon. It was expensive!


@SailorJerry - Congrats on your new baby! How exciting!

My understanding is that the glucose test is standard care for OBs - not so much midwives. I felt like you did; I didn't like the idea of drinking all that sugar just to see if I had a problem with sugar! I had no other symptoms of gestational diabetes (no sugar in the urine, etc.). Instead of the glucose tolerance test, a fasting blood draw can give you some helpful information.

That's what my doc recommended as an alternative. I came in first thing in the morning before breakfast. They didn't make at big deal at all out of my not wanting the test. But like I said, the test is standard, so it's something for you and our wife to discuss with your caregiver.


My wife is expecting and her doctor wants her to do the 1 hour glucose test. But I don't like the idea of her drinking the sugary drink. Is this test really necessary if there aren't any other indications of gestational diabetes? Are there any alternatives?

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