ObjectivesThis study aimed to assess the prevalence of self-medication (SM), the reasons for SM and the relationship between chronic health conditions and SM among adult individuals.SettingThis was an online questionnaire-based cross-sectional study disseminated on different social media platforms in Saudi Arabia.ParticipantsSaudi Arabia sample of adult individuals aged 18 and above.Primary and secondary outcome measuresPrimary outcome was SM, measured using the following question: ‘During the past 6 months, have you used any medicines or dietary supplements, or herbal medicines or vitamins not prescribed or recommended by a doctor?’ A positive answer indicates a self-medicated participant.ResultsOut of 1645 individuals who viewed the study link, 1295 participants completed the survey with a response rate of 95.1%. Overall, 989 (76.4%) participants reported practicing SM in the past 6 months. SM was higher among younger participants, women, those with higher education levels and high income, and working in the health field. About 198 (73.3%) who have chronic conditions practised SM for chronic health conditions, such as (hypertension and hypercholesterolemia). Previous experience with the same illness (n=530, 25.7%) and attempting to save time (n=466, 22.6%) were the main reasons behind SM, according to the participants. Adverse drug events were reported by 204 (20.6%) of self-medicating individuals and 274 (64.9%) of them reported discontinuing SM.ConclusionsThe findings of this study indicate a high prevalence rate of SM among the adult population in Saudi Arabia. Individuals with chronic health conditions reported a high rate of SM. Launching public education campaigns to improve public awareness of the harms of SM if misused, especially among those with chronic health conditions, is essential.