|BLOOD GLUCOSE TEST|
The following tests may be used for screening and diagnosis of type 1, type 2 or prediabetes.
If the initial screening result from one of the tests is abnormal, the test is repeated on another day. The repeat result must also be abnormal to confirm a diagnosis of diabetes.
· Fasting glucose (fasting blood glucose, FBG): this test measures the level of glucose in the blood after fasting for at least 8 hours.
· 2-hour glucose tolerance test (GTT): for this test, the person has a fasting glucose test done, then drinks a 75-gram glucose drink. Another blood sample is drawn 2 hours after the glucose drink. This protocol "challenges" the person's body to process the glucose.
Normally, the blood glucose level rises after the drink and stimulates the pancreas to release insulin into the bloodstream. Insulin allows the glucose to be taken up by cells. As time passes, the blood glucose level is expected to decrease again. When a person is unable to produce enough insulin, or if the body's cells are resistant to its effects (insulin resistance), then less glucose is transported from the blood into cells and the blood glucose level remains high.
· A different test called hemoglobin A1c may be used as an alternative to glucose testing for screening and diagnosis.
Sometimes a blood sample may be drawn and glucose measured when a person has not been fasting, for example, when a comprehensivemetabolic panel (CMP) is performed. If the result is abnormal, it is typically followed up with a fasting blood glucose test or a GTT.
Glucose blood tests are also used to screen pregnant women for gestational diabetes between their 24th and 28th week of pregnancy. The American Diabetes Association and the U.S. Preventive Services Task Force recommend that pregnant women not previously known to have diabetes be screened and diagnosed, using either a one-step or two-step approach. The American College of Obstetricians and Gynecologists (ACOG) recommends the two-step approach.
· One-step 2-hour oral glucose tolerance test (OGTT). After a fasting glucose level is measured, a woman is given a 75-gram dose of glucose to drink and her glucose levels are measured at 1 hour and 2 hours after the dose. Only one of the values needs to be above a cutoff value for diagnosis.
- Perform a glucose challenge test as a screen: a woman is given a 50-gram glucose dose to drink and her blood glucose level is measured after 1 hour.
- If the challenge test is abnormal, perform a 3-hour oral glucose tolerance test. After a woman's fasting glucose level is measured, she is given a 100-gram glucose dose and her glucose is measured at timed intervals. If at least two of the glucose levels at fasting, 1 hour, 2 hour, or 3 hour are above a certain level, then a diagnosis of gestational diabetes is made.
Glucose testing is also used to test women who were diagnosed with gestational diabetes 6-12 weeks after they have delivered their baby to detect persistent diabetes.
Signs of diabetes