ObjectiveTo evaluate how diet, exercise, and substance use influence serum etonogestrel concentrations among contraceptive implant users. Study designWe conducted a cross-sectional analysis of healthy, reproductive-age etonogestrel implant users. We assessed participants’ current diet, exercise, and substance (alcohol, tobacco, marijuana) use habits while simultaneously measuring serum etonogestrel concentrations. We used linear modeling to test for associations between survey responses and etonogestrel concentrations. ResultsAmong 115 participants, exercise habits and substance use had no significant associations with etonogestrel concentrations, while increased caloric intake demonstrated inconsistent associations. ConclusionThe lifestyle factors of diet, exercise, and substance use do not influence steady-state pharmacokinetics among contraceptive implant users. Clinical trial registrationClinicaltrials.gov, NCT03092037.