The Joslin Diabetes Blog has some details. For example:
Current standards for blood glucose meters were established by the FDA in 2003 in conjunction with the International Organization for Standardization (ISO). Today’s requirements state that a blood glucose system (meter and strips) must meet an accuracy standard of being within 20 percent of reference values (laboratory) for numbers at or above 75mg/dl and within 15mg/dl below 75 mg/dl.
The FDA has been working on revising the current requirements since 2010 and the ISO has already come out with new standards. Whether the FDA will accept the ISO’s recommendations or adopt a different set of standards only time will tell.
The article also mentions various factors that may affect accuracy, including temperature extremes, humidity, and altitude. The user manual that comes with the device should explain these.