[Many pitfalls in "simple" measuring of glucose in blood and plasma].

The measurement of plasma glucose concentrations is a cornerstone in the diagnosis and monitoring of diabetes mellitus. Kits for on-the-spot measurement of blood glucose are widely available both at healthcare facilities and in the patients' homes. Although measurement techniques have improved considerably in recent years, their optimal use is still dependent on the user's knowledge, skill and judgement. Fundamental pre-analytical, analytical, and post-analytical aspects of the measurement of blood glucose are presented in the article for the aid of healthcare personnel and patients alike. The new diagnostic criteria for diabetes mellitus are also presented, and their implications in different clinical situations are discussed.