PURPOSE: This study aims to characterize assisted reproductive technology patients' online discussions of fertility supplements to better understand how this audience uses supplements, their attitudes toward perceived effects of the supplement, and the topics patients sought advice on regarding supplements. METHODS: This study used mixed methods, sequential exploratory design. We extracted public posts from the Reddit forum, "r/IVF." Posts about fertility supplements were categorized by the described use of supplements and perceived effect of the supplement. Posts in each qualitative category were then quantified, and post author characteristics were analyzed using descriptive statistics. RESULTS: Three hundred sixty-nine posts were included in the analysis. Two hundred nine posts identified specific supplements, and the most frequently mentioned included ubiquinone, vitamin D, omega-3 fatty acids, dehydroepiandrosterone, and myo-inositol. Two hundred seventy-nine authors reported taking supplements; 9.3% reported a positive perceived effect, 12.9% reported a negative perceived effect, and 21.1% asked for advice regarding their supplements. In the remaining 90 posts, 10% of authors expressed concerns and 90% expressed interest in taking supplements. One hundred ninety-seven posts included the indication for using assisted reproductive technology, the most common being diminished ovarian reserve or male factor infertility. CONCLUSION: Many patients are using supplements with the goal of increasing their chance of assisted reproductive technology success and are seeking guidance on their use online. Some frequently mentioned supplements have limited research and unknown efficacy. The extensive discourse about supplements observed in this study reflects a need for increased guidance and evidence-based medical advice on how patients may use supplements safely and appropriately.