If you’re referring to the headline “Pharmacist issues warning to anyone who takes Vitamin D,” the warning is mainly about taking unnecessarily high doses, not about vitamin D itself being dangerous.
Vitamin D is an essential nutrient, but because it is fat-soluble, excessive supplementation can cause toxicity. Very high levels can lead to too much calcium in the blood, causing nausea, vomiting, weakness, excessive thirst/urination and kidney stones; severe toxicity can damage the kidneys and affect heart rhythm.
What dose is considered too much?
For most adults, the NIH lists 4,000 IU (100 mcg) per day as the tolerable upper intake level from all sources. That’s an upper safety limit—not a recommended daily dose. A doctor may deliberately prescribe higher amounts for a limited period when treating a documented deficiency.
The important warning
Be particularly careful if you’re taking several supplements that contain vitamin D. It’s easy to accidentally add together a multivitamin, vitamin D tablet and calcium/vitamin D product.
Vitamin D can also interact with certain medicines. For example, combining vitamin D with thiazide diuretics can increase the risk of excessively high calcium levels, while steroids and some other medicines can affect vitamin D status.
