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Blood Glucose
Results
Normal
A blood glucose test measures the amount of a type of sugar, called glucose, in your blood.
Results are often ready in 1 to 2 hours. Glucose levels in a blood sample taken from your vein (called a blood plasma value) may differ a little than glucose levels checked with a finger stick.
|
Fasting blood glucose: |
70–99 milligrams per deciliter or less than 5.5 mmol/L |
|---|---|
|
2 hours after eating (postprandial): |
70–145 mg/dL (less than 7.9 mmol/L) |
|
Random (casual): |
70–125 mg/dL (less than 7.0 mmol/L) |
Normal results may vary from lab to lab. Many conditions can change your blood glucose levels. Your health professional will discuss any significant abnormal results with you in relation to your symptoms and medical history.
High values
You may have diabetes. But your doctor will not use just one test result to diagnose you with the condition.
- The
American Diabetes Association (ADA) criteria for
diagnosing
diabetes are met when any of the following results
have been repeated on at least two different days:
- A fasting blood glucose level is 126 mg/dL (7.0 mmol/L) or higher.
- A 2-hour oral glucose tolerance test result is 200 mg/dL (11.1 mmol/L) or higher. For more information, see the medical test Oral Glucose Tolerance Test.
- Symptoms of diabetes are present and a random blood glucose test is 200 mg/dL (11.1 mmol/L) or higher. Symptoms of diabetes include increased thirst and frequent urination (especially at night), unexplained increase in appetite, unexplained weight loss, fatigue, erection problems, blurred vision, and tingling or numbness in the hands or feet.
- If your fasting blood glucose level measures in the range of 100 mg/dL (5.5 mmol/L) to 125 mg/dL (6.9 mmol/L), you are considered to have prediabetes (impaired fasting glucose), and you have an increased chance of getting diabetes.
- Other conditions that can cause high blood glucose levels include severe stress, heart attack, stroke, Cushing's syndrome, medicines such as corticosteroids, or excess production of growth hormone (acromegaly).
Low values
A fasting glucose level below 40 mg/dL (2.2 mmol/L) in women or below 50 mg/dL (2.8 mmol/L) in men that is accompanied by symptoms of hypoglycemia may mean you have an insulinoma, a tumor that produces abnormally high amounts of insulin.
Low glucose levels also may be caused by:
- Addison's disease.
- Decreased thyroid hormone levels (hypothyroidism).
- A tumor in the pituitary gland.
- Liver disease, such as cirrhosis.
- Kidney failure.
- Malnutrition or an eating disorder, such as anorexia.
- Medicines used to treat diabetes.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- Eating or drinking less than 8 hours before a fasting blood test or less than 2 hours before a 2-hour postprandial test.
- Drinking alcohol.
- Illness or emotional stress, smoking, and caffeine.
Taking a medicine, such as birth control pills, medicines used to treat high blood pressure, phenytoin (Dilantin), furosemide (Lasix), triamterene (Dyrenium, Dyazide), hydrochlorothiazide (Esidrix, Hydro Par, Oretic), niacin, propranolol (Inderal), or corticosteroids (prednisone), can cause changes in your test results. Make sure that your doctor knows about any medicines you take and how often you take them.
WebMD Medical Reference from Healthwise
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