Why do two blood glucose meters show different blood glucose results?

Each meter is characterized by parameters such as accuracy (compliance with the actual state) and precision (repeatability of measurement). For both parameters, deviations are permissible, since the measurement with a glucometer is not used for diagnosing diabetes, but for self-monitoring. The only reference result to which the one obtained with a glucometer can be compared is the level of glucose measured by the laboratory method (from venous blood collected in the laboratory). This means that the result given by the meter may differ from the actual level of glucose in the blood, and individual glucose meters may therefore differ from each other. Sometimes the manufacturer does not provide precise accuracy information in its materials, but may include information that its equipment meets the EN ISO 15197:2015 standard. It requires that 95% of blood glucose measurements taken with a glucose meter are within an error interval of no more than ±15 mg/dl (0.83 mmol/l) of the reference glucose measurement