Symptoms of Vitamin D Toxicity

Vitamin D is also known as the 'sunshine vitamin' and belongs to the group of fat soluble vitamins. It is also considered as a prohormone, or a precursor to hormone and is the only vitamin that can be naturally synthesized by human skin on exposure to the ultraviolet radiation of sunlight. It is mainly required by our body to maintain the normal level of blood calcium and phosphorus. By facilitating the absorption of calcium and phosphorus, vitamin D ensures proper growth of bones and teeth. It strengthens the immune system and is available in two main forms, ergocalciferol or vitamin D2 and cholecalciferol or vitamin D3. A deficiency of vitamin D can impair the normal absorption of calcium and phosphorus and is known to cause rickets in children and osteomalacia and osteoporosis in adults.

Excess of Vitamin D
A deficiency of vitamin D can either result from inadequate exposure to sunlight or insufficient dietary intake as well as absorption. Sometimes, even if it is absorbed, the body cannot convert it to an active form, mainly in conditions like liver, kidney and hereditary diseases. In addition to these, older individuals are more likely to suffer from vitamin D deficiency, as the ability of the skin to produce this vitamin declines with advancing age. Therefore, many individuals have to take supplementation of vitamin D to meet the daily requirement.

But most of the people taking vitamin D supplementation are unaware of the fact that this vitamin can be toxic if present in higher than the required amount. This is known as vitamin D toxicity, which can result either from a single overdose of supplementation or intake of small doses for a prolonged time period. Higher levels of this vitamin in the body can give rise to some really serious consequences or side effects.

Vitamin D Toxicity Signs
When the level of vitamin D increases in the body, it also raises the level of calcium in blood. The obvious result of this condition is hypercalcemia or presence of abnormally high level of calcium in blood. Hypercalcemia is responsible for producing most of the symptoms. The early symptoms include, gastrointestinal disorders like anorexia, diarrhea, constipation, nausea and vomiting. Bone pain, drowsiness, continuous headache, irregular heartbeat, loss of appetite, muscle and joint pain are some other early symptoms that are likely to appear within few days or weeks after a vitamin D overdose.

The individuals are also likely to experience alternating periods of constipation and diarrhea due to the presence of excessive vitamin D. Frequent urination, especially at night, excessive thirst, weakness, nervousness and itching are some other common symptoms of this condition. Kidney diseases have been found to be commonly associated with severe vitamin D toxicity, which can lead to elevated protein level in blood, formation of urinary casts and kidney stones, abnormal level of calcium in urine. It has been also found to increase the risk of ischaemic heart disease. An overdose for a very long period can lead to the development of calcium crystals in the soft tissues of the body. High blood pressure and kidney failure are the main complications associated with this condition.

Though our skin can synthesize vitamin D in the presence of sunlight, prolonged exposure to sunlight cannot cause toxicity. Toxicity is also less likely to be produced by the intake of vitamin D rich foods like salmon, mackerel, tuna, sardines, soy products, seaweeds, legumes, beans, and milk and dairy products. The most important risk factor for vitamin D toxicity is taking vitamin supplements. So adequate precautionary measures should be followed while taking vitamin D supplementation. Individuals taking vitamin D supplementation should consult a physician regarding the appropriate or safe doses of vitamin D and remain vigilant for the symptoms of toxicity.