The relationship between health care and climate change is an emerging area of study. This review describes several ways climate change impacts diagnostic safety, such as the challenges associated with diagnosing new climate-related pathogens, and how overuse of low-value diagnostic tools contributes to high greenhouse gas emissions. Public health policies could encourage patients and providers to reduce low-value, high-emission diagnostic care by selecting only appropriate tests and treatments and support efforts to train providers on documenting climate-related diagnosis (e.g., sequela from heatwave).