"PURPOSE: Blood glucose meters (or monitors) are used to test your blood sugar level. In order for the human body to function normally, the level of sugar in the blood must be within a specific, and narrow range. Blood glucose meters are used by individuals with diabetes mellitus, a condition where the body cannot process the sugar contained in food into energy.
METERS: There are many types and brands of blood glucose meters and each model may have different features. 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 monitors measure the glucose in whole blood while most lab tests measure the glucose in plasma. There are many monitors 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."
"If you test your blood glucose four times in a row with the same meter, using test strips from the same batch, your blood glucose is likely to be slightly different each time. How can that be? Meters aren’t always consistent. More important than consistency, though, is meter accuracy, or how close your meter results are on average to lab results.
Meters now are required under an international standard to produce results within a 20 percent margin of error, but the Food and Drug Administration is pressing for a tougher standard. Yet, even though home blood glucose tests can vary from lab tests and often are inconsistent, “almost all current meters are accurate enough to help you make good decisions about your therapy,” says David Marrero, PhD, J.O. Ritchey Professor of Medicine in the Division of Endocrinology and Metabolism at Indiana University’s School of Medicine. Despite the considerable margin of error, Marrero says, analyses show that meters are generally not so far off that “you would make an incorrect therapy decision” and, say, eat glucose tabs instead of injecting yourself with insulin. (Consumer Reports publishes ratings of blood glucose meters, including their accuracy.)
So What Can You Do?
Your meter’s control solution remains the best tool for making sure that your meter and test strips are working properly. Marrero recommends that you run the control solution—a liquid that has a known glucose level—through the meter when you first purchase it, and every time you open a new box of strips. “A good meter will run reliably,” explains Marrero, “but the thing that breaks down is not the meter; it’s the strips.” At the very least, you should test with control solution if your blood glucose results do not seem right. Some companies have stopped including control solution with new meters, so you may need to buy it over the counter for about $15. Insurance may cover the purchase. The solution expires after 30 days.
Doubts about meter accuracy make it all the more important to record your blood glucose readings in a logbook and to get regular A1C tests at the doctor’s office. If you’ve kept close tabs on your diet and exercise, and your A1C is still unexpectedly high, it’s much more likely to be a result of your testing times and technique (which your health care provider can help you pinpoint by reviewing your logbook) than of an inaccurate meter."
