Metformin—a cheap, safe, and widely available diabetes drug—could reduce the incidence of long covid if given during the acute phase of covid-19, a new study indicates.

A two week course of metformin given within three days of testing positive for SARS-CoV-2 led to 40% fewer long covid diagnoses over the following 10 months compared with people who had taken placebo, according to a randomised controlled trial.