Blood Sugar Tests
Blood sugar tests include several different tests that measure the amount of sugar (glucose) in a person's blood. These tests are done either on an empty stomach, or after consuming a meal or pre measured glucose drink. Blood sugar tests are done primarily to diagnose and evaluate a person with diabetes mellitus.
There are a variety of ways to measure a person's blood sugar.
Whole blood glucose test
Whole blood glucose testing can be performed by a person in his or
her home, and kits are available for this purpose. The person pricks
his or her finger (a finger stick) with a sterile sharp blade from
the kit. A single drop of blood is placed on a strip in a portable
instrument called a glucometer. The glucometer quickly determines the
blood sugar and shows the results on a small screen in usually a few
seconds.
Fasting plasma glucose test
The fasting plasma glucose test is done on an empty stomach. For the eight hours before the test, the person must fast (nothing to eat or drink, except water). The person's blood is drawn from a vein by a healthcare work. The blood sample is collected into a tube containing an anticoagulant. Anticoagulants stop the blood from clotting. In the laboratory, the tube of blood spins at high speed within a machine called a centrifuge. The blood cells sink to the bottom and the liquid stays on the top. This straw-colored liquid on the top is the plasma. To measure the glucose, a person's plasma is combined with other substances. From the resulting reaction, the amount of glucose in the plasma is determined.
Oral glucose tolerance test
The oral glucose tolerance test is done to see how well the body handles a standard amount of glucose. This test measures the amount of glucose in a person's plasma before and two hours after drinking a large premeasured beverage containing glucose. The person must eat a consistent diet, containing at least 5.25oz (150 g) of carbohydrates each day, for three days before this test. For eight hours before the test, the person must fast. A healthcare provider draws the first sample of blood at the end of the fast to determine the glucose level at the start of the test. The healthcare provider then gives the person a beverage containing 2.6 oz (75 g) of glucose. Two hours later, the person's blood is drawn again. These blood samples are centrifuged and processed in the laboratory. A doctor can then compare the before and after glucose levels to see how well the body processed the sugar.