For many people, blood glucose meter accuracy becomes a concern when they purchase a new meter and compare it with their old one, or go to the doctor to have a laboratory test. They may notice a seemingly large difference between the two test results.

At first glance, you would expect all blood glucose meters and laboratory equipment to give the same result. After all, they're measuring the same thing-the amount of glucose in a specific blood sample. But meters and lab equipment may be calibrated, or set, to measure blood glucose in different ways and will give different results.

Plasma-calibrated meters
While all home blood glucose meters use whole blood to measure glucose, lab equipment uses only the plasma portion of blood, meaning the red blood cells are removed before glucose is measured. Because of this difference in sample types, whole blood test results are approximately 12 percent lower than plasma test results. Some blood glucose meters are already calibrated, or set, to give a "plasma" test result, making this conversion unnecessary. For an accurate comparison of your blood glucose meter to a laboratory result, you must first know how your meter is calibrated.

Whole blood-calibrated meters
Whole blood-calibrated meters require a simple mathematical conversion to compare their test results with laboratory test results. Plasma-calibrated meters do not require a conversion and their results may be compared directly with laboratory test results. Whether you use one meter type or the other, it is important to note that both are accurate and neither is superior to the other. Just as with the Celsius and Fahrenheit scales measuring temperature or miles and kilometers measuring distance, both meter types measure the same thing-your blood glucose level.