This guideline covers vitamin D use in the context of COVID‑19. It is for adults, young people and children in hospitals and community settings. Vitamin D is important for bone and muscle health. It may also have a role in the body's immune response to respiratory viruses. On 14 July 2022, we removed the content on vitamin D for treating COVID-19 and added information on this into NICE’s COVID-19 rapid guideline on managing COVID‑19. When using this guideline, follow the usual professional guidelines, standards and laws (including those on equalities, safeguarding, communication and mental capacity), as described in making decisions using NICE guidelines.