In March, as coronavirus deaths in the UK began to mount, two hospitals in northeast England began taking vitamin D readings from patients and prescribing them with extremely high doses of the nutrient. Studies had suggested that having sufficient levels of vitamin D, which is created in the skin’s lower layers through the absorption of sunlight, plays a central role in immune and metabolic function and reduces the risk of certain community-acquired respiratory illnesses. But the conclusions were disputed, and no official guidance existed. When the endocrinology and respiratory units at Newcastle upon Tyne Hospitals NHS foundation trust made an informal recommendation to its clinicians to prescribe vitamin D, the decision was considered unusual. “Our view was that this treatment is so safe and the crisis is so enormous that we don’t have time to debate,” said Dr Richard Quinton, a consultant endocrinologist at the Royal Victoria Infirmary in Newcastle.