Potential Side Effects of Vitamin D (Hypervitaminosis D)

Cases of toxicity with Vitamin D are extremely uncommon - side effects can be sometimes severe if the daily toxicity threshold is exceeded

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Cases of toxicity with Vitamin D are extremely rare.  However, when an individual exceeds the daily toxicity threshold for the vitamin, the results can sometimes be severe, with myriad complications.

Recommended daily allowance for Vitamin D

The recommended daily allowance for Vitamin D, with regards to healthy individuals, varies with age and gender. The normal recommended daily allowance (RDA) value for Vitamin D, as set forth by the Food and Nutrition Board at the Institute of Medicine of The National Academies, is as follows:

Cool Vitamin D Potential Side Effects Tolerable Upper Levels Table

Daily toxicity threshold for Vitamin D

The daily toxicity threshold for Vitamin D is between 10,000-40,000 UL/day. Toxicity occurs once the daily threshold for the vitamin exceeds 50,000 IU/day over the course of long term use, which could be described as taking the vitamin in excess dosage, for the duration of a few months or more.

Side effects associated with Vitamin D toxicity

The side effects associated with Vitamin D toxicity include vomiting, constipation, nausea, muscle weakness, poor appetite, weight loss, confusion, fatigue, dehydration, and polyuria (excess urination). However, there are complications that can be somewhat more severe. Hypercalcemia (excessive amounts of calcium in the blood), which can develop from Vitamin D toxicity, harms organs such as the kidneys and the heart. Hypercalcemia also contributes to a few of the complications previously mentioned, such as constipation, muscle weakness, dehydration, fatigue and polyuria.

Excess amounts of calcium build up in tissues and accumulate in blood vessels, which can lead to kidney stones and arrhythmia (irregular heartbeat). In severe cases, an individual could possibly develop cardiac arrest.

Women who are pregnant have to be extremely careful. Maternal Hypercalcemia is known to cause birth defects, which include mental retardation, as well as facial deformities of the child. Moreover, while breastfeeding, it is imperative for the mother not to exceed the necessary daily requirement of Vitamin D for the infant, which can be achieved by limiting the use of supplements. (Women often take Vitamin D supplements in conjunction with calcium supplements during pregnancy to maintain proper nutrition.)

Depending on how long an individual has been exceeding the toxicity threshold, and the damage done to tissues and organs, treatment for Vitamin D toxicity will vary. Most often, discontinuing the use of supplements (Vitamin D and calcium), will alleviate most signs and symptoms. In severe cases, such as massive calcium deposits that build up in blood vessels within the heart (which will crystallize), surgery may be needed.

References

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  • Institute of Medicine, Food and Nutrition Board. (2010). Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press.
  • NIH Office of Dietary Supplements. (2009). Dietary Supplement Fact Sheet: Vitamin D.
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  • Wolpowitz D and Gilchrest B. (2006). The vitamin D questions: how much do you need and how should you get it? J Am Acad Dermatol 54:301-17.