Blood glucosestix and reflectometers are widely used in measurement of blood glucose in general practice. This study has investigated the accuracy and precision of this method at nine general practitioners' offices. The results show a strong trend towards less accurate and exact values with declining values of blood glucose. The authors ask for routines for quality control of these methods in general practice. Today this method, when used in general practice, is neither accurate nor precise enough to make the diagnose diabetes mellitus, unless the diagnose is obvious, with very high values of blood glucose and classical symptoms.