The warning is worth taking seriously—but it doesn’t mean everyone should stop taking vitamin D.
Vitamin D is important for bone and muscle health, and supplements can be appropriate when someone is deficient. The main concern is excessive supplementation, particularly high-dose products taken for long periods without medical supervision. Too much vitamin D can raise calcium levels and potentially cause nausea, vomiting, weakness, excessive thirst/urination, kidney stones, kidney damage, and abnormal heart rhythms. Office of Dietary Supplements+1
For adults, the generally established upper intake level is 4,000 IU (100 mcg) per day from all sources, although a clinician may deliberately prescribe more temporarily to treat a documented deficiency. Office of Dietary Supplements+1
Also be cautious if you take certain medicines. Vitamin D can interact with thiazide diuretics, and other medications can affect vitamin D absorption or levels. Office of Dietary Supplements
Bottom line: Vitamin D isn’t inherently dangerous; the issue is taking an inappropriate dose. Check the strength on your bottle (for example, 1,000, 2,000, 5,000, or 50,000 IU) and consider your other supplements before taking additional vitamin D.
