Vitamin D deficiency is a problem for national health systems worldwide: according to the Opinder Sahota study (2014), 1 billion people globally are estimated to have vitamin D deficiency, particularly among the elderly.

Vitamin D exists in two forms: D2 (ergocalciferol), obtained from yeasts and plants, and D3 (colecalciferol), obtained from diet or through the use of multivitamins. In addition to improving bone health, vitamin D has excellent immune-stimulating properties, which are especially useful for low immune defences. Although the lack of this substance is more of a public health issue than ever before, the other side of the coin, excess vitamin D, cannot be ignored. This is a rare phenomenon but it can have serious consequences for the health of consumers.

In this article we will explore the causes, toxicity signals and suggested doses of vitamin D, providing important information to better understand and manage this condition.

Causes of excess vitamin D

Excess vitamin D can come from a variety of sources, first and foremost the intake of massive doses of supplements, especially if outside of any type of medical check-up. Although hypervitaminosis is mainly caused by an overdose of supplements, in rarer cases too much vitamin D may result from dietary sources. For example, a diet where oils such as fish liver are abused can lead to an imbalance in the body. Even excessive exposure to sunlight can cause your skin to overproduce. It should be stressed, however, that this very uncommon. Vitamin D toxicity is more likely to be triggered by the frequent use of artificial solar lamps.

Signs of vitamin D toxicity

The symptoms of hypervitaminosis D can be varied. As vitamin D3 promotes absorption of calcium from the gastrointestinal tract, excess calcium can lead to significant hypercalcaemia. This increase in calcium levels in the blood can lead to a number of problems, including gastrointestinal disorders and an abnormal accumulation of calcium in the bones, soft tissues, heart and kidneys.

What are the symptoms of high vitamin D? Among the most common clinical signs are:

  • Dehydration
  • Vomiting
  • Diarrhoea
  • Decreased appetite
  • Irritability
  • Constipation
  • Fatigue
  • Muscle weakness
  • Soft tissue calcification

But severe abuse of vitamin D could also cause long-term complications, including:

  • Kidney stones
  • Kidney damage
  • Renal impairment
  • Calcification (induration) of the arteries and soft tissues

Because vitamin D is stored in adipose tissue and gradually released into the bloodstream, side effects can continue for several months. For this reason, it is essential to consult a doctor if you suspect vitamin D intoxication, so that you can check the levels of calcium and cholecalciferol in your blood and then start appropriate therapy.

What is the right dosage of vitamin D?

Determining the safe dose of vitamin D is essential to avoid the above issues and to preserve the health of consumers. For most of the adult population, exceeding 100 micrograms per day increases the risk of side effects. For children between 1 and 10 years, a dose of below 50 micrograms per day is considered safe.


In conclusion, high vitamin D3 can lead to several health side effects, so it is a possibility that both industry and the general population needs to be aware of. Understanding the causes, recognising the signs of toxicity and complying with the recommended doses is the first step to improving consumer welfare and providing safe indications.