The discrimination between therapeutic and abusive use of drugs in sports is performed using threshold concentrations or reporting levels, and the detection of the substances in a sample is only reported as an adverse analytical finding when the concentration exceeds the threshold or the reporting level. In this paper, the strategies of discrimination and the analytical methods used for the main groups of substances where the distinction is needed (β-2 agonists, ephedrines, glucocorticoids and morphine) will be reviewed. Nowadays, LC-MS is the method of choice for the analysis of these substances and, in most of the cases, a simple dilution of the urine sample is performed before the chromatographic analysis.

The financial support received from Consell Català de l’Esport and DIUE (2014 651 SGR 692) (Generalitat de Catalunya, Spain) and the World Antidoping Agency 652 (grants 13D22RV and 14D06RV) is acknowledged