Glucose tolerance test
Alternative names:
GTT; OGTT; oral glucose tolerance test
What the risks are:
People with known diabetes or hypoglycemia are not typically given this test. If people with these conditions have a reaction during the test, medication can be administered.
Risks from venipuncture include: - excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Special considerations:
Interfering factors: Drugs that may cause glucose intolerance include antihypertensives, anti-inflammatory drugs (NSAIDs), beta-blockers - oral, furosemide (see furosemide - oral), nicotine, oral contraceptives (birth control pills), psychiatric drugs, corticosteroids and thiazide diuretics.
Some patients are unable to tolerate a glucose load of 100 g (due to, for example, prior gastrectomy, short bowel syndrome, or malabsorption). In these cases, an intravenous GTT can be performed with slightly different normal values.
Veins and arteries vary in size from one patient 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.
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