A glucose meter, also called a glucose monitor, is a small, portable device designed for home use that checks levels of glucose (blood sugar) for the management of diabetes. The meter warns people with diabetes when glucose levels are out of range.

Target blood glucose range is a personalized number given by a physician. It is usually based on factors such as age, presence of diabetic complications or other medical conditions, and tendency to have hypoglycemia unawareness (difficulty sensing symptoms of low glucose).

In general, normal plasma blood glucose levels for people with diabetes are 90 to 130 milligrams per deciliter (mg/dL) before meals and 110 to 150 mg/dL at bedtime. Whole blood readings are set at 80 to 120 mg/dL before meals and 110 to 150 mg/dL at bedtime, according to the American Diabetes Association (ADA).

Checking glucose levels with a typical meter requires a person to place a small sample of blood on a test strip. Test strips are coated in chemicals that combine with glucose. The strip is read by the monitor, which measures how much glucose is present. Meters measure glucose in different ways. Some measure the amount of electricity that can pass through the blood sample. Others measure how much light reflects from it. The meter digitally displays the glucose level as a number in milligrams per deciliter (mg/dL) that can be recorded for glucose monitoring.

The meter is matched to each new box of glucose testing strips through a process called coding. Manually coded meters require the user to enter a code number or insert a code strip or code chip into the device. Automatically coded meters set the correct code whenever a test strip is inserted and may result in greater accuracy.

Accurate readings are essential for management of glucose. Mechanical and human error can cause inaccuracy. Some meters come with a standard control solution that has a known concentration of glucose. The solution can be tested and compared to the meter’s results. Other monitors test accuracy with electronic controls. With this method a cartridge or special test strip is placed in the meter and a signal appears to indicate that the meter is working properly.

Patients are advised to bring their glucose meter with them on diabetes appointments. When a meter reading is recorded a few minutes before blood is drawn for laboratory tests, the results can be compared for accuracy.

To use most glucose meters, complete the following steps:

1. Wash hands with soap and dry thoroughly. If drawing blood from an area besides the finger, wash and dry that area. If soap and water are not available, sterilize the sample site with alcohol.
   
   
2. Prepare the meter. Because each meter works differently, read the instructions carefully.
   
   
3. Choose the spot. Draw blood from different spots to allow healing.
   
   
4. Prepare the lancet and lancing device. Finger-pricking devices vary, so read instructions carefully.
   
   
5. Place the lancing device against the side of the finger or at an alternate site (area other than the finger) and press the button. Meters are different, so make sure the meter is approved for alternate site testing.
   
   
6. Hold the hand down and hold the finger to squeeze out a drop of blood.
   
   
7. Place the blood on the test strip and put the test strip in the meter according to the manufacturer’s directions. With some models the blood is placed on the strip after it has already been inserted into the meter. Read meter directions carefully.
   
   
8. Use a gauze, tissue or cotton ball to wipe clean any blood and control bleeding at the puncture site.
   
   
9. Record the results. Recorded meter results will tell a physician how a patient’s diabetes care plan is working. It will also allow the patient to monitor how food, exercise, stress and medicines affect glucose.
   
   
10. Dispose of the lancet in a secure container with a lid.

Because not all glucose monitors work in the same way, patients should get training from a certified diabetes educator on how to use their meter and interpret results. The educator should supervise the test to ensure that the patient is using the meter properly. A physician can also periodically view the patient’s testing method to ensure that self-tests are being completed properly.