Blood Glucose Testing

Glucose is a simple sugar found in food. When in blood, it is called blood glucose or blood sugar. Glucose testing records the level of glucose in the blood at one time, or over a period of time.

Blood glucose tests are commonly used to screen for diabetes. Diabetes is a disease that causes abnormally high blood glucose levels. It is important to detect and control diabetes early, because it can lead to a variety of serious complications over time.

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 glucose test. It measures glucose in blood after going 12 to 14 hours without food. The person must also stop taking some drugs, since they can alter the results. A high glucose level obtained on 2 or more tests may indicate diabetes. Other conditions may show low glucose levels. If the person's blood sugar drops too low, weakness, restlessness, hunger, or sweating may occur.

Another test is the 2-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 and then fasts for 2 hours before giving blood. Strenuous exercise and smoking during the fast should be avoided.

An oral glucose tolerance test is still another method used to evaluate borderline cases of glucose problems. The person follows a high carbohydrate diet for 3 days and then fasts for 10 to 16 hours. During this time, any drugs that can alter the test are not taken. 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 to 6 hours. A nurse or technician periodically draws a blood sample and collects urine. There may be 4 or more blood draws. The pattern of glucose levels 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. Blood glucose testing may be needed.

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