Too much of good thing: Scientists warn vitamin D overuse can turn toxic

Vitamin D, often dubbed the “sunshine vitamin,” is widely taken to support bone health and immunity — but scientists are warning that excessive supplementation can have serious, and sometimes dangerous, side effects.

Researchers say that while vitamin D deficiency remains a global health concern, rising use of high-dose supplements is leading to a growing number of toxicity cases.

Too much vitamin D can push calcium levels in the blood too high, a condition known as hypercalcemia, which may result in kidney stones, bone pain, nausea, fatigue, and muscle weakness. In severe cases, it can damage organs and require hospital treatment, ScienceAlert writes.

Doctors emphasise that most people who develop toxicity recover once supplements are stopped and calcium levels are treated. However, experts warn that misuse — often through incorrect dosing or misunderstanding prescriptions — is a key driver of cases, particularly among children and older adults.

Public health data from the United States suggest a sharp rise in reported vitamin D toxicity over the past two decades, with thousands of cases linked to accidental overdosing. In some instances, individuals were unknowingly taking far more than the recommended daily amount due to labeling confusion or prescribing errors.

Experts remain divided on how much vitamin D is truly optimal, but most guidelines suggest adults should not exceed around 4,000 IU per day unless medically advised. Health authorities stress that sunlight exposure and diet often provide sufficient vitamin D for many people, reducing the need for high-dose supplements.

Medical professionals are urging caution as supplement use continues to grow, advising people to consult healthcare providers before starting or increasing vitamin D intake.

By Aghakazim Guliyev