Blood Glucose

2-hour Postprandial Blood Sugar Test, Fasting Blood Sugar Test, Random Blood Sugar Test

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.

Blood glucose

Fasting blood glucose:	70–99 milligrams per deciliter (3.9–5.5 mmol/L)
2 hours after eating (postprandial):	70–145 mg/dL (3.9–8.1 mmol/L)
Random (casual):	70–125 mg/dL (3.9–6.9 mmol/L)

 

Normal results may vary from lab to lab. 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.

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 (5.6 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.

Go to previous section	Go to top of page	Go to next section
Author:	Christine Wendt, R.D., L.D.	Last Updated: July 14, 2009
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
© 1995-2010 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.