Climate change has become an increasingly important threat to freshwater systems, with rising temperatures and extreme thermal variability impacting ectotherms. Fish are left with little capacity to cope with the fluctuations of climatic events, including temperature changes in their environment. By replicating heat fluctuations in the lab, we can better understand the effects of heat stress on fish. As metabolites play a crucial role in physiological processes, by observing alterations of metabolites found in fish, we can enhance our understanding of these processes. We exposed 95 Fathead minnows (Pimephales promelas) to heat treatment tanks (34°C) and normal tanks (24°C) over a 7-day period. The temperature in the heat treatment tanks were gradually increased to 34°C over a span of 3 days (day -2, day-1, day 0). On Day 8, blood glucose was measured, and the fish were euthanized, dissected, mucus, plasma, gill, and brain samples were collected. Upon completion of the experiment, we observed statistically significant changes in the abundance of metabolites from the Fathead minnows, suggesting an impact on the temperature of Fathead minnow health.