Key Points Question Do US states and intravenous (IV) hydration spa sites vary in policy, regulation, and practice? Findings In this mixed-methods study examining state policies and site practices across all 50 US states and the District of Columbia, it was found that state-level policies governing IV hydration spas vary widely, with only 4 states comprehensively addressing all facets of regulation; facility practices also varied with regard to product offerings, product claims, and staffing.