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Glucose tolerance test - non-pregnant
Oral glucose tolerance test - non-pregnant; OGTT - non-pregnant; Diabetes - glucose tolerance test; Diabetic - glucose tolerance test
The glucose tolerance test is a lab test to check how your body breaks down sugar.
Tests to screen for diabetes during pregnancy are done differently.
Tests to screen for diabetes during pre...
A glucose screening test is a routine test during pregnancy that checks a pregnant woman's blood glucose (sugar) level. Gestational diabetes is hi...
How the Test is Performed
The most common glucose tolerance test is the oral glucose tolerance test (OGTT).
Before the test begins, a sample of blood will be taken.
You will then be asked to drink a liquid containing a certain amount of glucose (usually 75 grams). Your blood will be taken again every 30 to 60 minutes after you drink the solution.
The test may take up to 3 hours.
A similar test is the intravenous (IV) glucose tolerance test (IGTT). It is rarely used, and is never used to diagnose diabetes. With IGTT, glucose is injected into your vein for 3 minutes. Blood insulin levels are measured before the injection, and again at 1 and 3 minutes after the injection. The timing may vary.
How to Prepare for the Test
Make sure you eat normally for several days before the test.
DO NOT eat or drink anything for at least 8 hours before the test. You cannot eat during the test.
Ask your health care provider if any of the medicines you take can affect the test results.
How the Test will Feel
Drinking the glucose solution is similar to drinking very sweet soda.
Serious side effects from this test are very uncommon. With the blood test, some people feel nauseated, sweaty, lightheaded, or may even feel short of breath or faint after drinking the glucose. Tell your doctor if you have a history of these symptoms related to blood tests or medical procedures.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
Glucose is the sugar the body uses for energy. People with untreated diabetes have high blood glucose levels.
Diabetes
Diabetes is a chronic disease in which the body cannot regulate the amount of sugar in the blood.
Most often, the first tests used to diagnose diabetes in people who are not pregnant are:
- Fasting blood glucose level: diabetes is diagnosed if it is higher than 126 mg/dL (7 mmol/L) on 2 different tests
- Hemoglobin A1c test: diabetes is diagnosed if the test result is 6.5% or higher
Glucose tolerance tests are also used to diagnose diabetes. The OGTT is used to screen for, or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.
Normal Results
Normal blood values for a 75 gram OGTT used to check for type 2 diabetes in those who are not pregnant:
- Fasting: 60 to 100 mg/dL (3.3 to 5.5 mmol/L)
- 1 hour: less than 200 mg/dL (11.1 mmol/L)
- 2 hours: less than 140 mg/dL (7.8 mmol/L)
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
A glucose level that is higher than normal may mean you have pre-diabetes or diabetes:
- A 2 hour value between 140 and 200 mg/dL (7.8 and 11.1 mmol/L) is called impaired glucose tolerance. Your doctor may call this "pre-diabetes." It means you are at increased risk of developing diabetes over time.
- A glucose level of 200 mg/dL (11.1 mmol/L) or higher is used to diagnose diabetes.
Serious stress to the body, such as from trauma, stroke, heart attack, or surgery, can raise your blood glucose level. Vigorous exercise can lower your blood glucose level.
Some medicines can raise or lower your blood glucose level. Before having the test, tell your provider about any medicines you are taking.
Risks
You may have some of the symptoms listed above under the heading titled "How the Test will Feel."
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
References
Pagana KD, Pagana TJ. Blood studies. In: Pagana KD, Pagana TJ, eds. Mosby's Manual of Diagnostic and Laboratory Tests . 5th ed. St Louis, MO: Elsevier Mosby; 2014:chap 2.
Selph S, Dana T, Blazina I, Bougatsos C, Patel H, Chou R. Screening for type 2 diabetes mellitus: a systematic review for the U.S. Preventive Services Task Force. Ann Intern Med . 2015;162(11):765-776. PMID: 25867111 www.ncbi.nlm.nih.gov/pubmed/25867111 .
Standards of medical care in diabetes-2016: summary of revisions. Diabetes Care . 2016;39 Suppl 1:S4-S5. PMID: 26696680 www.ncbi.nlm.nih.gov/pubmed/26696680 .
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Urine sample - illustration
A "clean-catch" urine sample is performed by collecting the sample of urine in midstream. Men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. A small amount of urine should initially fall into the toilet bowl before it is collected (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. The container is then given to the health care provider.
Urine sample
illustration
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Fasting glucose tolerance test - illustration
The fasting glucose tolerance test is the simplest and fastest way to measure blood glucose and diagnose diabetes. Fasting means that you have had nothing to eat or drink (except water) for 8 to 12 hours before the test. You are diagnosed with diabetes if your blood glucose level is 126 mg/dl or greater on two separate tests.
Fasting glucose tolerance test
illustration
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Oral glucose tolerance test - illustration
During the oral glucose tolerance test your blood glucose is tested two hours after drinking 75 grams of glucose. You are diagnosed with diabetes if your blood glucose level is 200 mg/dl or greater.
Oral glucose tolerance test
illustration
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Urine sample - illustration
A "clean-catch" urine sample is performed by collecting the sample of urine in midstream. Men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. A small amount of urine should initially fall into the toilet bowl before it is collected (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. The container is then given to the health care provider.
Urine sample
illustration
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Fasting glucose tolerance test - illustration
The fasting glucose tolerance test is the simplest and fastest way to measure blood glucose and diagnose diabetes. Fasting means that you have had nothing to eat or drink (except water) for 8 to 12 hours before the test. You are diagnosed with diabetes if your blood glucose level is 126 mg/dl or greater on two separate tests.
Fasting glucose tolerance test
illustration
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Oral glucose tolerance test - illustration
During the oral glucose tolerance test your blood glucose is tested two hours after drinking 75 grams of glucose. You are diagnosed with diabetes if your blood glucose level is 200 mg/dl or greater.
Oral glucose tolerance test
illustration
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Diabetes
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Diabetes - type 1
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Diabetes - type 2
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Diabetes diet
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Review Date: 7/24/2015
Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Internal review and update on 09/01/2016 by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
