Diabetes: Choosing and Using Your Glucose Meter (cont.)

FDA requires that glucose meters and the strips used with them have instructions for use. You should read carefully the instructions for both the meter and its test strips. Meter instructions are found in the user manual. Keep this manual to help you solve any problems that may arise. Many meters use "error codes" when there is a problem with the meter, the test strip, or the blood sample on the strip. You will need the manual to interpret these error codes and fix the problem.

You can get information about your meter and test strips from several different sources. Your user manual should include a toll free number in case you have questions or problems. If you have a problem and can't get a response from this number, contact your healthcare provider or a local emergency room for advice. Also, the manufacturer of your meter should have a website. Check this website regularly to see if it lists any issues with the function of your meter.

New devices are for sale such as laser lancets and meters that can test blood taken from "alternative sites" of the body other than fingertips. Since new devices are used in new ways and often have new use restrictions, you must review the instructions carefully.

Important Features Of Glucose Meters

There are several features of glucose meters that you need to understand so you can use your meter and understand its results. These features are often different for different meters. You should understand the features of your own meter.

Measurement Range. Most glucose meters are able to read glucose levels over a broad range of values from as low as 0 to as high as 600 mg/dL. Since the range is different among meters, interpret very high or low values carefully. Glucose readings are not linear over their entire range. If you get an extremely high or low reading from your meter, you should first confirm it with another reading. You should also consider checking your meter's calibration.

Whole Blood Glucose vs. Plasma Glucose. Glucose levels in plasma (one of the components of blood) are generally 10-15% higher than glucose measurements in whole blood (and even more after eating). This is important because home blood glucose meters measure the glucose in whole blood while most lab tests measure the glucose in plasma. There are many meters on the market now that give results as "plasma equivalent". This allows patients to easily compare their glucose measurements in a lab test and at home. Remember, this is just the way that the measurement is presented to you. All portable blood glucose meters measure the amount of glucose in whole blood. The meters that give "plasma equivalent" readings have a built in algorithm that translates the whole blood measurement to make it seem like the result that would be obtained on a plasma sample. It is important for you and your healthcare provider to know whether your meter gives its results as "whole blood equivalent" or "plasma equivalent."

Cleaning. Some meters need regular cleaning to be accurate. Clean your meter with soap and water, using only a dampened soft cloth to avoid damage to sensitive parts. Do not use alcohol (unless recommended in the instructions), cleansers with ammonia, glass cleaners, or abrasive cleaners. Some meters do not require regular cleaning but contain electronic alerts indicating when you should clean them. Other meters can be cleaned only by the manufacturer.

Display Of High And Low Glucose Values. Part of learning how to operate a meter is understanding what the meter results mean. Be sure you know how high and low glucose concentrations are displayed on your meter.

Factors That Affect Glucose Meter Performance

The accuracy of your test results depends partly on the quality of your meter and test strips and your training. Other factors can also make a difference in the accuracy of your results.

Hematocrit. Hematocrit is the amount of red blood cells in the blood. Patients with higher hematocrit values will usually test lower for blood glucose than patients with normal hematocrit. Patients with lower hematocrit values will test higher. If you know that you have abnormal hematocrit values you should discuss its possible effect on glucose testing (and HbA1C testing) with your health care provider. Anemia and Sickle Cell Anemia are two conditions that affect hematocrit values.

Other Substances. Many other substances may interfere with your testing process. These include uric acid (a natural substance in the body that can be more concentrated in some people with diabetes), glutathione (an "anti-oxidant" also called "GSH"), and ascorbic acid (vitamin C). You should check the package insert for each meter to find what substances might affect its testing accuracy, and discuss your concerns with your health care provider.

Altitude, Temperature and Humidity. Altitude, room temperature, and humidity can cause unpredictable effects on glucose results. Check the meter and test strip package insert for information on these issues. Store and handle the meter and test strips according to the instructions.

Third-Party Test Strips. Third-party or "generic glucose reagent strips" are test strips developed as a less expensive option than the strips that the manufacturer intended the meter to be used with. They are typically developed by copying the original strips. Although these strips may work on the meter listed on the package, they could look like strips used for other meters. Be sure the test strip you use is compatible with your glucose meter.