Oral Glucose Tolerance Test: Results
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Results
The oral glucose tolerance test (OGTT) measures the body's ability to use a type of sugar, called glucose, that is the body's main source of energy.
Normal
Normal glucose levels in a blood sample taken from your vein (called a plasma glucose value) may vary from lab to lab.
| 50 grams (g) of glucose | 1-hour: | Less than 140 milligrams per deciliter (mg/dL) or 7.8 millimoles per liter (mmol/L) |
|---|
If values are between 140–180 mg/dL (7.8–10.2 mmol/L), a glucose tolerance diagnostic test may be recommended.
| 100 g of glucose | Fasting: | Less than 95 mg/dL or 5.2 mmol/L |
|---|---|---|
| 1-hour: | Less than 180 mg/dL or 10.0 mmol/L | |
| 2-hour: | Less than 155 mg/dL or 8.6 mmol/L | |
| 3-hour: | Less than 140 mg/dL or 7.7 mmol/L |
| 75 g of glucose | 2-hour: | Less than 140 mg/dL or 7.8 mmol/L |
|---|
High values
High glucose levels may be caused by:
- Gestational diabetes.
- Polycystic ovary syndrome (PCOS).
- Taking medicines, such as corticosteroids, niacin, phenytoin (Dilantin), some diuretics, and some medicines used to treat high blood pressure, HIV, or AIDS.
- Severe stress.
- Large amounts of the hormone cortisol in the blood (Cushing's syndrome).
- Inherited diseases, such as cystic fibrosis, or hemochromatosis.
- Overproduction of growth hormone (acromegaly).
- Pheochromocytoma.
Low values
Low glucose levels may be caused by:
- Certain medicines, such as medicines used to treat diabetes, some blood pressure medicines (such as propranolol), and some medicines for depression (such as isocarboxazid).
- A condition that prevents the intestines from absorbing nutrients from food, such as celiac disease.
- Decreased production of the hormones cortisol and aldosterone (Addison's disease).
- Problems with the thyroid gland (hypothyroidism) or an underactive pituitary gland.
- A tumor of the pancreas (insulinoma).
- Inflammation and scarring of the liver (cirrhosis).
Many conditions can change blood glucose levels. Your health professional will discuss any significant abnormal results with you in relation to your symptoms and medical history.
| Last updated: | July 25, 2007 |
|---|---|
| Author: | Caroline Rea, RN, BS, MS |
| Reviewed By: | Caroline S. Rhoads, MD - Internal Medicine, Alan C. Dalkin, MD - Endocrinology |
| Editors: | Susan Van Houten, RN, BSN, MBA, Tracy Landauer |
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