This randomized, double-blind, placebo-controlled, within-patient crossover trial evaluated whether a vapocoolant (cold) spray applied before subcutaneous insulin injection reduces injection pain compared with a placebo (sterile-water) spray in adults treated in a tertiary-care emergency department. Each participant received a cold spray before one clinically indicated insulin injection and a placebo spray before another, in randomized order, and marked injection pain on a 100-mm visual analog scale 10 seconds after each injection. The within-patient design allowed each participant to serve as their own control.