Glucose is the form of sugar in the blood. Blood glucose testing records the level of glucose in the body at one time or over a period of time. Blood glucose tests are commonly used to screen for diabetes. Diabetes is a disease that includes abnormally high blood glucose levels. Diabetes can lead to a variety of serious complications over time. Therefore, it is important to detect and control it early.

Glucose tests usually require drawing blood from the arm. A nurse or technician can perform this in less than 3 minutes. There is usually only slight discomfort from the blood draw.

A common test is a fasting plasma glucose test. It measures glucose in blood after a 12 to 14 hours without food. The person must also stop taking some drugs, since they can alter the results. If the person's blood sugar drops too low, he or she may have weakness, restlessness, hunger, or sweating. A high glucose level obtained on 2 or more tests may indicate diabetes. There are several conditions that result in low glucose levels.

Another test is the two hour postprandial plasma glucose test. It is useful when fasting results are borderline. The person eats a balanced meal containing about 100 grams of carbohydrates. He or she then fasts for 2 hours before giving blood. He or she should avoid strenuous exercise and smoking after the meal.

An oral glucose tolerance test is the most sensitive method to evaluate borderline cases of diabetes. The person follows a high carbohydrate diet for 3 days. He or she then fasts for 10 to 16 hours and must stop taking any drugs that can alter the test. At the beginning of the test the person swallows a standard amount of glucose. The healthcare provider then monitors plasma and urine glucose levels for 3 hours. Sometimes the test must last up to 6 hours. A nurse or technician periodically draws a blood sample and collects urine. There may be 4 or more blood draws, which could cause some discomfort. The pattern of glucose over time helps diagnose diabetes or low blood sugar disorders.

Talk to your healthcare provider if you think you are experiencing symptoms related to high or low blood sugar. He or she may suggest blood glucose testing.

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