Information About Fasting Blood Sugar Test

Submitted on March 27, 2012

Glucose is a vital source of energy for the body, and it mainly comes from foods that are high in carbohydrates. Optimal levels of glucose are required for the body for its normal functioning; however, high or low levels can be the cause of many diseases.

Fasting Blood Sugar Test

The fasting blood sugar test is used to measure the amount of glucose in the blood. It may also be called a blood glucose level test. The results of this test help to diagnose if an individual already has diabetes or a pre-diabetes condition, and to assess the progress of diabetes treatment. It is also used to identify if an individual has a low glucose level, leading to a condition called hypoglycemia.

The test is called a fasting test, because it requires the individual to avoid eating or drinking anything except water for 8 hours before the test. To perform this test, an elastic band is tightened around the upper arm and blood is drawn from the vein using a needle. After collection of the blood sample, a cotton swab containing antiseptic alcohol is provided to clean the area that was pricked.

How Is it Measured?

Fasting blood sugar is measured as mg/Dl or milligrams per deciliter. A fasting blood glucose value between 70 to 99 mg/Dl is considered normal. Pre-diabetes blood sugar lies in the range of 100 to 125 mg/Dl. Any value above 126 mg/Dl indicates that the individual being tested has diabetes.

Causes of High Blood Glucose Levels

High blood glucose levels, if left untreated, can have serious consequences such as damage to the eyes, kidney, nerves, and blood vessels. They can also be a cause of

  • Feeling thirsty constantly
  • Fatigue
  • Blurred vision
  • Increased urination
  • Infections and wounds that heal slowly

Causes of Low Blood Glucose Levels

Blood glucose levels that are lesser than 40mg/Dl are considered to be low. Low blood sugar levels can also be the cause of some conditions such as

  • Addison's disease
  • Hypothyroidism or a reduced thyroid hormone levels
  • Liver disease
  • Failure of the kidney
  • Eating disorders such as anorexia

Diabetes medication is also known to sometimes reduce the blood glucose values.

It is important to know that high blood glucose levels can be caused even if the individual does not have diabetes. Heart attack, stroke, extreme stress, and some medications can also cause the blood sugar levels to go high. The results of the test can also vary due to certain medications and birth control pills.