You may consume many different types of sugar in your diet. The cells in your body, however, depend on the simplest form -- monosaccharides -- to generate the energy to function and reproduce. Normal blood sugar levels are uniform for men and women; a normal fasting blood glucose level is less than 110 mg/dL.
Sugar in the Blood
Glucose is a simple sugar that your cells absorb from your bloodstream and convert to energy to fuel your body. More complex carbohydrates such as fructose, a fruit sugar, or lactose, a milk sugar, are digested and eventually broken down to form glucose. Your cells cannot absorb glucose without the presence of insulin, however. Insulin is a hormone produced in your pancreas that also travels in your bloodstream and allows glucose to move into the cell. An abnormally high blood sugar level indicates insufficient insulin secretion, impaired insulin sensitivity or a combination of the two conditions.
Fasting Blood Glucose Test
The most popular test for blood sugar is the fasting blood glucose, or FBG, test. To prepare for this test, you must fast starting at midnight the day of your blood draw. Health care providers use this test to screen for diabetes. A healthy fasting blood glucose level is less than 100 mg/dL. An FBG of 110 tp 125 mg/dL indicates prediabetes or impaired fasting glucose. An FBG of 126 mg/dL or greater on at least two occasions is used to diagnose diabetes mellitus.
Oral Glucose Tolerance Test
Health care providers also use the oral glucose tolerance test, or OGTT, or oral glucose challenge to measure blood glucose levels. The OGTT measures fasting plasma glucose as well as the body's ability to metabolize a known amount of glucose. To run this exam, you consume a liquid solution containing a certain amount of dissolved glucose. Your blood is drawn before and after drinking the solution. For a 75-g glucose solution, normal blood sugar values 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. A blood glucose level of 200 mg/dL or greater indicates diabetes mellitus.
Casual or Random Blood Glucose
If a patient has symptoms of diabetes, a physician can order a casual or random blood glucose test. This test does not require fasting. A casual blood glucose level of 200 mg/dL or greater and symptoms of diabetes can be used to diagnose the condition.
Testing Frequency
The U.S. National Institutes of Health recommends that adult men and women obtain a fasting blood glucose test once every three years beginning at 45 years of age. The NIH recommends earlier and more frequent testing for diabetics and people at-risk for diabetes including those with obesity; a family history of diabetes; high blood pressure; high blood lipids; or who self-identify with a high-risk racial or ethnic group including African Americans, Native Americans, Hispanic Americans, Asian Americans and Pacific Islanders.
References
- "Present Knowledge in Nutrition, Eighth Edition"; Bowman, B.; 2001
- MedLine Plus: Glucose Tolerance Test; 2010
- "Absorption of Monosaccharides"; Bowen, R.; 2006
