Veterans With Diabetes International

Diabetes: How to Test Your Blood Glucose

Everyone with diabetes should test their blood glucose levels regularly. Knowing your blood glucose levels allow you to alter your diabetes management strategy if your levels aren't near your target blood glucose.

Also, regular testing of your blood glucose levels can reduce your risk of having long-term complications from diabetes. Based on studies of people with type 1 diabetes (Diabetes Control and Complications Trial [DCCT]) and type 2 diabetes (United Kingdom Prevention of Diabetes [UKPDS]), maintaining near normal blood glucose and HbA1c levels significantly reduces the risks of complications arising from diabetes.

Ways to Test Your Blood Glucose

Traditional Home Blood Glucose Monitoring. The traditional method of testing your blood glucose involves pricking your finger with a lancet (a small, sharp needle), putting a drop of blood on a test strip and then placing the strip into a meter that displays your blood sugar (glucose) level. Meters vary in features, readability (with larger displays or spoken instructions for the visually impaired), portability, speed, size and cost. Current devices provide results in less than 15 seconds and can store this information for future use. These meters can also calculate an average blood glucose level over a period of time. Some meters also feature software kits that retrieve information from the meter and display graphs and charts of your past test results. Blood glucose meters and strips are available at your local pharmacy.
Meters That Test Alternative Sites. Newer meters allow you to test sites other than your fingertip; these alternative testing sites include upper arm, forearm, base of the thumb and thigh. However, testing at alternative sites may give you results that are different from the blood glucose levels obtained from the fingertip. This is especially true when your blood glucose is rapidly changing, like after a meal or after exercise. It is also important to know that if you are checking your sugar at an alternative site while you are experiencing symptoms of hypoglycemia, you should not rely on these test results.
Lasers to draw blood. In 1998, a laser to draw blood was approved. The laser device produces a precise beam of light that penetrates the skin on the finger instead of pricking it, reducing pain and discomfort.
GlucoWatch. In 2001, the FDA approved the GlucoWatch, a watch-like device that helps people with diabetes measure their blood glucose via tiny electric currents. It draws small amounts of fluid from the skin and measures blood glucose levels three times per hour for up to 12 hours. The GlucoWatch is considered a first step toward noninvasive, continuous glucose monitoring, but it does have some shortfalls. According to the FDA, the device should not replace daily finger pricks. There are also other monitoring devices on the market; some allow blood to be drawn from the forearm, which is considered to be less painful than finger pricks, but all have their drawbacks.
When Should I Test My Blood Glucose?

Blood glucose testing is usually done before meals and at bedtime. Daily blood glucose checks are especially important for people on insulin or the sulfonylureas class of antidiabetes drugs.

Frequency and timing of blood glucose measurements should be individualized, but for most people with type 1 diabetes, self-monitored blood glucose checks are recommended three or more times daily.

For people with type 2 diabetes, it is not known what frequency is best for home monitoring, but it should be done often enough to help attain good blood glucose control. Your health care provider will tell you when and how often you should check your blood glucose.

Note: Remember that being sick complicates your diabetes. You may need to test your blood glucose more frequently when you are ill.

Conditions That Affect Your Blood Glucose

Certain conditions may interfere with an accurate reading of the blood glucose, and include:

Anemia
Gout
High air temperature
Humidity
If you are consistently seeing abnormal results, recalibrate your meter and check the strips.

The chart below gives you an idea of where your blood glucose level should be throughout the day. Your ideal blood glucose range may be different from another person's and will change throughout the day.

Time of Test Ideal for Adults With Diabetes
Before meals 90-130 mg/dL
Before bedtime snack 180 mg/dL
*Source: American Diabetes Association, position statement 2003

Home Blood Glucose Monitoring and HbA1c

Monitoring your HbA1c level is also important for diabetes control. Many home glucose monitors have the capacity to display an average blood glucose reading, which correlates with the HbA1c.

Learn more about HbA1c.

Average Blood Glucose Level (mg/dL) HbA1c (%)
129mg/ dL 6.3
146mg/ dL 7
169mg/ dL 8
192mg/ dL 9
214mg/ dL 10
237mg/ dL 11

When Should I Call My Doctor?

In most cases, a fasting blood glucose level more than 180 mg/dL is too high and a blood glucose level less than 70 mg/dL is too low. If your blood glucose is less than 70 mg/dL and you have more than one unexplained low blood glucose reaction a week, call your health care provider.

If your blood glucose is greater than 180 mg/dL for more than a week, or if you have two consecutive readings greater than 300 mg/dL, call your health care provider. In most cases, your doctor will suggest changes in your diabetes management plan.

How Do I Record My Test Results?

Keep good records of any blood, urine, or ketone tests you do. Your records can help alert you to any problems. Also, these test records help your health care provider make any needed changes in your meal plan, medicine, or exercise program. Bring these records with you every time you visit your health care provider.

Get tips on living with diabetes.
View the full table of contents for the Diabetes Guide.

Reviewed by Certified Diabetes Educators in the Department of Patient Education and Health Information and by physicians in the Department of Endocrinology at The Cleveland Clinic.

Edited by Brunilda Nazrio, MD, WebMD, October 2004.

Portions of this page The Cleveland Clinic 2000-2005