The fasting blood glucose test

A diabetes diagnosis can be scary, but if you've been feeling unwell there is relief in knowing the cause. For those who have experienced excessive thirst, frequent urination, and/or fatigue, a fasting blood glucose test may be ordered to determine blood glucose levels. Fasting (no food for at least 8 hours) stimulates the release of the hormone glucagon, which in turn raises plasma glucose levels.

The fasting blood glucose test: what is it?

The procedure. The test consists of a simple blood test, which is sent to a lab for analysis. Prior to being tested, a person must not to eat for 8 hours. Because of this fast, the test is usually conducted first thing in the morning after an overnight fast.

The results. Results for the fasting plasma glucose test traditionally fall into three result areas: normal, impaired and diabetes.

  1. Normal fasting glucose. Blood sugars under 100 mg/dL are considered normal for a fasting blood glucose test.
  2. Impaired (pre-diabetes). Individuals with blood sugars between 100 and 125 mg/dL are considered to have a form of pre-diabetes (impaired fasting glucose).
  3. Diabetes. If an individual tests at or above 126 mg/dL, a second test is traditionally ordered. If the the second test confirms the first test results, that individual has diabetes.

More about the fasting blood glucose test

Dr. Jennifer Perkins, an endocrinologist at Duke University says the fasting glucose test is not perfect, "a fasting sugar can miss populations that have normal fasting sugars, but abnormal postprandial sugars (like impaired glucose tolerance)." She adds, "it can be used as an inexpensive screening test for impaired fasting glucose and/or diabetes, however, it is largely being replaced by the hemoglobin A1c." (Hemoglobin A1c test provides an average of your blood sugar control over a six to 12 week period, and is used in conjunction with home blood sugar monitoring to make adjustments in your diabetes medicines.)

For those who have a normal fasting blood glucose result, but are at risk of developing diabetes (genetics, overweight, high risk ethnic groups, women who've had gestational diabetes and/or individuals with impaired fasting glucose or impaired glucose tolerance), a doctor may follow up with an oral glucose tolerance test (OGTT). This test is another method used to detect diabetes, and is usually done during pregnancy to diagnose gestational diabetes. It can also be used to diagnose pre-diabetes. The liquid is a cola like solution that is a designated amount of carbs (usualy 75 grams). Patients must fast for at least 8 hours before the test. Blood is drawn before consuming the drink, and again every 30 to 60 minutes after. This test can take up to 3 hours.

When it comes to your health, it's better to have a diagnosis than to remain in the dark. If you are experiencing these symptoms, talk to your doctor about a glucose test. The sooner you have an answer, the sooner you give your body what it needs.

About Amy Stockwell Mercer

Amy Stockwell Mercer is a freelance writer living in Charleston, SC.

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