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.

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what?s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Blood glucose

Fasting blood glucose:2	Less than or equal to 110 milligrams per deciliter (mg/dL) (6.1 millimoles per liter, or mmol/L).
2 hours after eating (postprandial):3	Less than 140 mg/dL (7.8 mmol/L) for people age 50 and younger; less than 150 mg/dL (8.3 mmol/L) for people ages 50-60; less than 160 mg/dL (8.9 mmol/L) for people age 60 and older.
Random (casual):2	Levels vary depending on when and how much you ate at your last meal. In general: 80-120 mg/dL (4.4-6.6 mmol/L) before meals or when waking up; 100-140 mg/dL (5.5-7.7 mmol/L) at bedtime.

Many conditions can change your blood glucose levels. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.
For more information on results from an oral glucose tolerance test or glycohemoglobin A1c test, see the topic Oral Glucose Tolerance Test or Glycohemoglobin A1c.

High values

You may have diabetes. To make a diagnosis of type 2 diabetes, your doctor will use the American Diabetes Association's criteria.
Other conditions that can cause high blood glucose levels include:

• Severe stress.
• Heart attack.
• Stroke.
• Cushing's syndrome.
• Medicines such as corticosteroids.
• 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, Oretic), niacin, propranolol (Inderal), or corticosteroids (prednisone). Some medicines can cause changes in your test results. Make sure that your doctor knows about any medicines you take and how often you take them.