The “sunshine vitamin” may come with a dark side. Just as a lack of vitamin D can lead to health dangers, so too can an excess. For years now, scientists have warned that not everyone needs to take vitamin D supplements, and that, in rare cases, high-dose versions can be toxic, especially for young kids and older adults. As the supplement grows in popularity, it’s more important now than ever that patients and doctors are aware of the dose and the downsides. The risks might be rare, but they’re on the rise, and in the worst-case scenarios, they can be life-threatening.
Too much vitamin D raises calcium absorption, which can lead to hypercalcemia, in which calcium forms dangerous deposits in arteries or soft tissues. This can raise the risk of kidney stones, disrupt bone metabolism, and bring on a whole host of nasty symptoms, including nausea, vomiting, constipation, fatigue, muscle weakness, or bone pain. The vast majority of people recover from vitamin D toxicity after the supplements are discontinued and they receive IV fluids or medication to lower calcium levels. But in rare cases, if left untreated, vitamin D toxicity can lead to kidney failure requiring hemodialysis, or even cause fatal intestinal bleeding.
