Measure blood glucose levels by using a meter that determines how much glucose is present in the blood, as the American Diabetes Association describes. Insert a test strip in the meter, and lance a finger to obtain a drop of blood. Then, hold the test strip against the blood before reading the meter's blood glucose measurement. Some meters have spring-loaded lancing devices, and some allow the blood to be drawn from the thigh, hand or forearm.
The accuracy of a glucose meter is tested in three different ways, according to the Food and Drug Administration. A liquid control solution is a vial containing a liquid with a predetermined amount of glucose, and the tester compares the results from this solution with the value printed on the label. Electronic checks are performed when a glucose meter is turned on, and if an error code is returned, the device's manual explains how to correct it. A meter's performance can also be tested against the results from a laboratory by comparing the results of the lab report to the results shown on the meter.
Factors that can affect the accuracy of a glucose meter include substances such as uric acid and vitamin C, hematocrit levels, the quality of the meter and test strips, and environmental conditions, notes the Food and Drug Administration. A meter's instructions should specify substances that might skew the results. Dehydration and anemia can affect hematocrit levels. Temperature, humidity and altitude may also affect a meter's results.