ABSTRACT Meldonium has been developed in the 70s in Latvia and is currently used in a limited number of countries for heart‐related diseases, such as heart attack, failure, or angina pectoris. Due to its metabolic properties (decrease of lactate production, increase of glycogen use, and protective action again oxidative stress), meldonium has been abused by numerous athletes to enhance their performance. The drug has been prohibited by the World Anti‐Doping Agency since 2016 and is on the S4.4.3 list (metabolic modulators) of the prohibited substances at all times. As athletes can challenge their anti‐doping violation involving meldonium, there is an interest in testing for it in hair in order to document their pattern of exposure. Such hair application can be complicated to develop, as meldonium has a chemical formula close to an amino acid and presents an ionized fraction, which are limiting factors for drug incorporation into hair. Liquid chromatography coupled to tandem mass spectrometry was used. The drug was extracted from hair after methanol incubation in an ultrasound bath and separation on a BEH HILIC column. Linearity was verified from 0.5 to 100 pg/mg ( R 2 = 0.9943). The limit of detection was 0.1 pg/mg. Although their meldonium regimen was unknown, the drug was identified in the proximal hair segment (0 to 1 cm) of three consumers at 0.7, 6.1, and 17 pg/mg, highlighting for the first time the incorporation in hair of this molecule.