Background <p>Eating disorders have one of the highest mortality rates of any mental illness. However, individuals experiencing an eating disorder are not the only people affected by their condition; informal caregivers (any individual who has a relationship to an individual with an eating disorder but may or may not be a designated caregiver by title) are also impacted by other’s eating disorders. Using the tripartite model of uncertainty, this study examines the ways that informal caregivers use online forums to express their uncertainty.</p> Methods <p>A random sample of the <i>r/EatingDisorders</i> subreddit was extracted and posts written by informal caregivers were identified, resulting in 163 posts for analysis. A deductive qualitative analysis was conducted using the tripartite model of uncertainty to identify sources of uncertainty for informal caregivers.</p> Results <p>Results concluded that individuals express medical, personal, and social uncertainty online independently, but also experience compounding uncertainty, where the experience of one uncertainty creates tension with and may exacerbate another uncertainty.</p> Conclusions <p>Future research should continue to explore the implications of compounding uncertainties to assist in the future creation of educational resources for individuals who may be informal caregivers of people with eating disorders.</p>