Hypervitaminosis

Hypervitaminosis refers to vitamin toxicity caused by excessive intake of vitamins. It is most commonly the result of high-dose supplements or the prolonged consumption of very large amounts of fortified foods. Fat-soluble vitamins A, D, E, and K tend to accumulate in body tissues and pose a greater risk than water-soluble vitamins, which are usually excreted. Toxicity can be acute after a single large dose or chronic after months of excess.

Causes include continued use of high-dose vitamin preparations, single-nutrient supplements such as vitamin A or vitamin D, fortified products, and accidental ingestions, especially in children. Certain medications contain vitamins as excipients. Dietary sources alone rarely cause toxicity unless there is extreme intake of liver, cod liver oil, or other rich animal-derived products.

Common toxicities involve fat-soluble vitamins, particularly vitamin A and vitamin D. Vitamin A excess can cause headaches, drowsiness, skin changes, and, with long-term use, liver enlargement and intracranial hypertension. Vitamin D toxicity produces hypercalcemia with weakness, polyuria, dehydration, and calcification of soft tissues. High doses of vitamin E may increase bleeding risk, and very high doses of niacin or B6 can cause flushing or neuropathy.

Symptoms are nonspecific at first and may include nausea, vomiting, malaise, and abdominal pain. Specific signs depend on the vitamin involved. Hypercalcemia from vitamin D toxicity is particularly dangerous, requiring medical evaluation. In pregnant individuals, excessive vitamin A is associated with birth defects. Children are especially vulnerable to accidental ingestion of vitamin-containing products.

Diagnosis relies on history of supplement use and laboratory testing tailored to the suspected toxin (eg, serum calcium for suspected vitamin D toxicity; reevaluation of retinol or 25-hydroxyvitamin D levels as indicated). Management centers on stopping the offending vitamin and treating complications. Prevention focuses on following established upper intake levels and consulting a clinician before high-dose supplementation.