Taking Too Much Vitamin D Can Backfire, Scientists Warn The “sunshine vitamin” may come with a dark side. Just as a lack of vitamin D can lead to health problems, an excess can be harmful too. For years, scientists have warned that not everyone needs to take vitamin D supplements and that, in rare cases, high doses can be toxic—especially for young children and older adults. As the supplement grows in popularity, it is more important than ever for patients and doctors to be aware of proper dosing and potential downsides. While the risks are uncommon, they are increasing and, in worst-case scenarios, can be life-threatening. Too much vitamin D increases calcium absorption, which can lead to hypercalcemia—a condition where calcium builds up in the blood and forms dangerous deposits in arteries or soft tissues. This raises the risk of kidney stones, disrupts bone metabolism, and can cause symptoms such as nausea, vomiting, constipation, fatigue, muscle weakness, and bone pain.

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Taking Too Much Vitamin D Can Backfire, Scientists Warn The “sunshine vitamin” may come with a dark side. Just as a lack of vitamin D can lead to health problems, an excess can be harmful too. For years, scientists have warned that not everyone needs to take vitamin D supplements and that, in rare cases, high doses can be toxic—especially for young children and older adults. As the supplement grows in popularity, it is more important than ever for patients and doctors to be aware of proper dosing and potential downsides. While the risks are uncommon, they are increasing and, in worst-case scenarios, can be life-threatening. Too much vitamin D increases calcium absorption, which can lead to hypercalcemia—a condition where calcium builds up in the blood and forms dangerous deposits in arteries or soft tissues. This raises the risk of kidney stones, disrupts bone metabolism, and can cause symptoms such as nausea, vomiting, constipation, fatigue, muscle weakness, and bone pain.

Most people recover from vitamin D toxicity once supplements are stopped and treatment—such as IV fluids or medications to lower calcium levels—is given. However, in rare cases, untreated toxicity can lead to kidney failure requiring dialysis or even fatal intestinal bleeding.

Some studies also suggest that older adults with high levels of vitamin D in their blood may have a higher risk of falls.

In a 2018 review, US researchers warned of “considerable complacency” regarding vitamin D’s potential toxic effects. Scientists still do not agree on exactly how much vitamin D is too much.

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