Health care providers commonly use several tests to measure blood sugar, which is an indication of how well your body is able to metabolize sugar and often used to diagnose diabetes mellitus. The normal range of blood sugar for adults depends on what test was used to measure your blood sugar level, with each test having its own reference value.
Normal Blood Sugar Levels
Normal blood sugar levels are the goal for all adults, including diabetics. A normal blood sugar concentration means your body is able to effectively metabolize sugar, moving it from your bloodstream into your cells where it is converted to energy. Your cells depend on insulin, a hormone produced in your pancreas, to receive glucose from your bloodstream. Abnormally high blood sugar levels indicate that sugar is not being metabolized properly as a result of insufficient insulin secretion, impaired insulin sensitivity or a combination of the two conditions.
Fasting Blood Glucose Levels
Fasting blood glucose, FBG, is the most common test used to measure blood sugar. A healthy fasting blood glucose level is less than 110 mg/dL. An FBG level of 110 to 125 mg/dL is an indication of prediabetes or impaired fasting glucose. An FBG level of 126 mg/dL or greater on at least two occasions is used to diagnose diabetes mellitus. To prepare for an FBG test, you must fast starting at midnight on the day of the blood draw. Measuring your blood sugar in a fasting state shows how completely the cells in your body are able to take up glucose from your bloodstream.
Oral Glucose Tolerance Test
Health care providers also use an oral glucose tolerance test, OGTT, otherwise known as an oral glucose challenge, to measure blood sugar levels. An OGTT measures fasting blood glucose as well as your body's ability to metabolize a concentrated glucose solution. The normal range for blood sugar depends on the amount of glucose in the solution. For example, normal blood sugar values for a 75g glucose solution are 60 to 110 mg/dL prior to drinking the solution, less than 200 mg/dL one hour after drinking the solution and less than 140 mg/dL two hours after drinking the solution.
Testing Recommendations
The U.S. National Institutes of Health, NIH, recommends that adult men and women obtain a fasting blood glucose test once every three years starting at 45 years of age. The NIH recommends earlier and more frequent testing for diabetics or people with predisposing conditions including obesity, a family history of diabetes, high blood cholesterol or blood pressure, or those who self-identify with a high-risk racial or ethnic group including Native-Americans, African-Americans, Hispanic-Americans, Asian-Americans or Pacific Islanders.
References
- MedlinePlus: Glucose tolerance test
- "Present Knowledge in Nutrition," Eighth Edition - Chapter 50. Diabetes Mellitus; Bowman, B.; 2001
