Background Self-administration of medicines or dietary supplements without any physician’s advice appears to be more frequently practiced by amateur athletes.

Objective The aim is to assess the prevalence of self-medication among amateur athletes who visit fitness centers and to identify the main factors influencing the self-medication. We postulate that the practice of self-medication among athletes attending fitness centers is high.

Design Cross-sectional study. Data was collected by an anonymous self-administrated questionnaire.

Setting The study was made in collaboration with 11 fitness centers in Liège (Belgium).

Patients (or Participants) Our final sample was composed of 338 amateur athletes.

Interventions (or Assessment of Risk Factors) We assessed the prevalence of self-medication based on the sex, age, BMI, socioeconomic status, health status, duration of club membership, hours spent at the club, number of sports activities at the club, types of activities practiced at the club.

Main Outcome Measurements The main measurement is the self-medication.

Results Almost half of our 338 amateurs (49.7%) visiting fitness centers admitted to self-medicate in the context of sport practice. Among them 36.4% take dietary complements and 22.5% used drugs. The probability of self-medication increases significantly with the number of hours of sports practice, with the participation to body-building group lessons and with the consumption of sports drinks. Furthermore, 20% of the substances consumed, whether self-medicated or not, contained potentially doping substances.

Conclusions We could highlight a significant prevalence of self-medication among amateur athletes visiting fitness centers. The intensity and frequency of sports practice seems to play a key-role regarding the decision to self-medication. Given the health risks entailed by these practices it seems crucial to implement information and prevention measures regarding self-medication. Moreover, it would be interesting to lead further research assessing the adverse consequences of self-medication among this specific population.