The copper IUD is a widely used contraceptive, recommended to many women who want a long-acting contraceptive method and sometimes seen as an alternative for those who want to avoid side effects associated with hormonal alternatives. However, while many report being satisfied with their copper IUD, a growing number of women speak about a range of mental and physical symptoms believed to be caused by copper excess due to copper IUD use. This set of systemic side effects may be framed as a rare disease but is not recognized as such by established medical authorities. In Sweden accounts about copper IUD related side effects circulate on social media, primarily in a Facebook group which presently includes over 9000 members.Based on online group interviews and written essays, we examine how women embracing these alternative knowledge claims navigate various sources of information, focusing the role of scientificity in these epistemic negotiations. We show that participants were strongly invested in scientificity and criticized medical authorities for not being scientific enough. Meanwhile, due to a perceived lack of scientifically based expertise on their condition, many of the women reported having little choice but to turn to alternative or non-scientific modes of health-related knowledge and practices. We argue that medical authorities’ tendencies towards portraying these women’s claims as unscientific simplify the nature of lay knowledge production, potentially deepening divides between medical authorities and parts of the public.