Glucose, the main energy source for cells and tissues, normally remains at a fairly constant level in the bloodstream. Levels of blood glucose vary during the day, so a normal reading after dinner will differ from a reading first thing in the morning. Insulin, made in the pancreas, facilitates the uptake of glucose into cells and tissues. Blood glucose levels rise when insulin production decreases or the cells become resistant to the action of insulin. Testing blood glucose levels at various times during the day determines whether a person has high glucose levels, indicating impaired insulin function and diabetes.
Determination
Blood glucose testing is done by taking a blood sample and testing it in the laboratory for glucose. Blood samples are taken from veins, usually in the arm.
Timing
Timing of blood glucose tests affects the interpretation of the results. Fasting blood tests are done first thing in the morning after a person hasn't had anything to eat or drink for at least eight hours. Random blood glucose levels, on the other hand, can be done any time, regardless of when the last meal was. Glucose tolerance test blood samples, often done during pregnancy to test for gestational diabetes, are taken one, two and three hours after a person drinks glucola, which contains a concentration of glucose. Normal results vary depending on the timing and type of test.
Results
Fasting blood glucose should fall between 70 and 110 mg/dL, or milligrams per deciliter. Random blood glucose levels should remain below 200 mg/dl, while oral glucose tolerance test results should fall less than 200mg/dL in nonpregnant women after two hours. Levels in pregnant women should be less than 190 mg/dL at one hour, less than 165 mg/dL at two hours and less than 145 mg/dL at three hours to rule out gestational diabetes, according to the Encyclopedia of Surgery.
Signifiance
Normal blood glucose levels indicate that a person has normal insulin levels and functioning and does not have diabetes.
Considerations
Some people have borderline glucose levels. The levels are not high enough to diagnose diabetes but fall at the top of or just above the normal range. These people are considered to have impaired glucose regulation or pre-diabetes and might develop diabetes in the future. Weight reduction of as little as 7 percent of total body weight can often reduce the risk of developing diabetes, according to the Merck Manual. Increasing exercise can also help prevent diabetes in people with impaired glucose metabolism.
