- Vitamin D is required by the human body for bone repair and growth, but because the body stores vitamin D, too much of it can be toxic. For vitamin D the Recommended Dietary Allowance (RDA) for an adult male is 400 IU daily, most of which is manufactured by the body. A vitamin D intake of three or four times the RDA can result in vitamin D toxicity.
- Excess intake of vitamin D results in a surplus of calcium and phosphorus in the blood, which causes deposits of calcium and phosphorus to form on the kidneys and soft tissues. Toxicity can also result in a wide variety of symptoms: nervousness, excessive thirst and urination, confusion, heart rhythm abnormalities, headaches, nausea, weakness, vomiting, joint pain and loss of appetite. If vitamin D toxicity is severe, kidney failure or kidney stones may develop.
- Vitamin D toxicity is diagnosed by the presence of clinical symptoms as well as the results of blood tests. Elevated serum level of vitamin D metabolites, high blood pressure and elevated blood calcium levels are all positive indicators of vitamin D toxicity. If the kidneys have been damaged the individual may also have an elevated protein level.
- Toxicity typically occurs only if supplements or megavitamins are consumed, since most foods do not contain enough vitamin D to cause illness. Symptoms of toxicity can appear months after high doses of vitamin D, and death from vitamin D overdose is extremely rare. Severe cases of vitamin D toxicity usually occur only from accidental poisoning.
- Vitamin D toxicity is first treated by discontinuing any vitamin D supplementation and limiting calcium intake. If the toxicity is severe, medications such as corticosteroids or bisphosphates may be given, along with fluids to encourage hydration. If kidney damage is present the kidneys are also treated.
