The self-monitoring of blood glucose through the use of instrumentation point of care testing is an essential component in the management of the diabetic patient, in order to achieve and maintain glycaemic control, prevent and identify hypoglycaemia, prevent severe hyperglycaemia, adjust lifestyle changes and establish the need to begin treatment with insulin in gestational diabetes mellitus. The factors that can affect the accuracy of the measurement of blood glucose meters and of all devices for decentralized analysis may occur essentially in all stages of the diagnostic process, from the pre-analytical to post-analytical phase. In addition, self-monitoring of blood glucose may have a role in improving metabolic control if it is part of a wider educational strategy. Since the accuracy of the measures obtained by the meter depends on both the instrument and the user, it is recommended that patients receive initial education in the proper use of instrumentation and interpretation of data to adjust therapy, skills that must then be revaluated in time.