Blood tests are available to diagnose diabetes and monitor sugar levels. Decades ago, people had to test their urine for the presence of sugar. This showed only that blood sugar levels were much too high. Today's diagnostic tools show both the present glucose level and the average blood sugar level of the past few months.
Blood Tests to Diagnose Diabetes
The diagnosis of diabetes is made by checking blood glucose levels. There are criteria for a fasting glucose test and for a glucose tolerance test.
The fasting glucose test requires the patient has nothing to eat or drink for 8 hours prior to the blood draw. Having food or drinks can affect the blood sugar level. According to Medline Plus, a website of the National Institutes of Health, a fasting level up to 100 mg/dL (milligrams per deciliter) is considered normal. Levels above 125 mg/dL indicate diabetes, and levels between 100 and 126 mg/dL may indicate pre-diabetes. At this point, further tests are usually conducted for definitive diagnosis.
The glucose tolerance test (GTT) is used to help diagnose diabetes when a fasting test is suggestive of diabetes or pre-diabetes. For the GTT, the patient drinks a measured amount of sweetened syrup. Blood is then drawn several times at scheduled intervals to monitor how the body processes the sugar. Lab Tests Online explains what the results indicate: Two hours after ingesting the syrup, a blood glucose level of less than 140 mg/dL is normal; readings between 140 and 200 mg/dL indicate pre-diabetes, and a value over 200 mg/dL is diagnostic of diabetes.
Blood Testing to Monitor Glucose at Home
Blood glucose levels can be easily monitored at home with a machine called a blood glucose meter, which is about the size of a cellular phone. According to Medline Plus, a testing kit can be purchased at a pharmacy without a prescription. A sanitary method is used to draw a drop of blood from the tip of the finger with a sharp tool called a lancet. The blood droplet is then placed on a chemically-treated strip of paper and inserted into the machine to be read. Within a minute, the blood sugar reading shows up as the number of mg/dL in the blood. This number informs the patient if the blood sugar is too high, too low, or within an acceptable range. Subsequently the patient can treat levels outside of the desired range.
Blood Testing to Monitor Long-Term Glucose Control
The hemoglobin A1c test is performed in a laboratory. This test shows a summary of levels over the past three months by measuring glucose attached to hemoglobin in the red blood cells. In addition to home blood glucose monitoring, Diabetes Monitor recommends that people with diabetes have this test performed twice a year as an indicator of long-term control. The American Diabetes Association explains the usefulness of this test by comparing it to a baseball player's stats: "Neither a single day's blood test results nor a single game's batting record gives the same big picture." Levels above 6.5 percent are undesirable.
