Glucose, or Blood Sugar

Diabetes is a health problem characterized by high levels of a type of sugar called "glucose" in the blood. Most people think of sugar as the white powder on the dinner table. That type of sugar is called sucrose. Glucose is a different sugar, and is the major fuel the body uses for energy. So when we say "high blood sugar" we mean high levels of glucose.

People with diabetes have high blood sugar because they do not have enough insulin in the blood to control their glucose level. Insulin is a hormone the body needs to store glucose. Over time, high blood glucose levels will hurt the heart, eyes, feet and kidneys. Because damage can occur without symptoms, it important to check your blood sugar level.

No one knows for sure when to routinely start checking your blood glucose level.

There are tests that can be used to check your blood sugar level to see if you have diabetes or have a chance of getting diabetes.

  • A random plasma glucose test is done randomly, no matter when you last ate. This test does not call for fasting.
  • A fasting plasma glucose (FPG) test calls for you to fast, or not eat anything, for at least eight hours before the test.
  • An oral glucose tolerance test (OGTT) also calls for you to fast for at least eight hours, except for a glucose-containing liquid you drink two hours before the test. This test is given by mouth.

A random blood glucose level of 200 milliliters (mL) per deciliter (dL) or higher can mean you have diabetes if you’re having any combination of these symptoms:

  • Increased urination
  • Increased thirst
  • Increased hunger
  • Increased fatigue
  • Unexplained weight loss
  • Blurred vision

Your doctor will most likely follow up with a FPG test or OGTT on a different day before making a diagnosis.

The FPG test is the most test used most often. Results from this test fall into one of these groups:


99 mg/dL or less


100–125 mg/dL


126 mg/dL or higher

The OGTT is more accurate than the FPG test in diagnosing pre-diabetes, which is when blood glucose levels are higher than normal but not high enough to be diagnosed as diabetes. Results fall into one of these groups:


139 mg/dL or less


140–199 mg/dL


200 mg/dL or higher

The American Diabetes Association suggests another method for diabetes screening — the A1C test, or the "average glucose test." This simple blood test measures the average of your blood sugar over a period of three months. Your doctor may order the test after a blood sugar test, or instead of it. The normal level for A1C is less than 6.5 percent.


Log in to your Blue Access® for Members account to learn more about diabetes and other conditions.

User ID:
Not registered?
Learn how to register
Take a tour