Abstract This recommendation aims to provide up-to-date information and the latest consensus on diabetes diagnosis from a group of experts in Germany. The disease diabetes mellitus is classified and its different types are described briefly. Options for diagnosis are presented including current cut-off values as well as reference intervals to recognize glucose utilization disorders like impaired fasting glucose or impaired glucose tolerance. Special attention is paid to the measurement value imprecision. The minimal difference (MD) is introduced as an excellent measure to distinguish measurement results which are analytically different from each other. Potential caveats considering pre-analytics in glucose measurement and limitations of HbA1c assessment for diagnosis of diabetes mellitus are presented. Taken together, this recommendation provides a comprehensive overview of the state of the art in diabetes mellitus diagnosis and also critically evaluates potential pitfalls. The aim of recommendations like this one issued by the German Diabetes Association is to provide the diabetologist and his team the information he needs for his daily practice. These recommendations are updated annually. They are written by a group of experts, but they are not evidence-based guidelines. This specific recommendation for diabetes diagnosis briefly describes the diabetes types and the different options for diagnosis. Also the caveats and the practical procedure are presented.