The warning is worth taking seriously only when it refers to excessive or inappropriate vitamin D supplementation. Vitamin D is an important nutrient for calcium absorption and bone health, but more isn’t necessarily better.
What pharmacists are usually warning about
- Too much vitamin D can raise blood calcium. This can cause nausea, vomiting, constipation, weakness, confusion, excessive thirst/urination and kidney stones. Severe toxicity can damage the kidneys and cause abnormal heart rhythms. Office of Dietary Supplements+1
- Toxicity almost always comes from excessive supplements, not from ordinary sunlight exposure. Office of Dietary Supplements
- For adults, the generally accepted upper daily intake is 4,000 IU (100 mcg) from all sources unless a clinician has specifically prescribed a higher dose for treatment. Office of Dietary Supplements+1
- Some people need particular caution—for example, those with kidney disease, high calcium levels, certain parathyroid disorders, or people taking thiazide diuretics. Vitamin D can also interact with some medicines. Office of Dietary Supplements+1
- A doctor may deliberately prescribe a dose above 4,000 IU for a limited period to treat a documented deficiency. That should be medically supervised, rather than self-prescribed. Office of Dietary Supplements
At age 83
Vitamin D can be important for maintaining bone health, but I wouldn’t recommend starting a high-dose supplement simply because it’s advertised as beneficial. If you’re already taking vitamin D, check the exact strength on the bottle—for example, 400 IU, 1,000 IU, 2,000 IU or 5,000 IU—and check whether you are also getting vitamin D from a multivitamin or calcium supplement.
If you tell me how many IU of vitamin D you take each day and whether you take calcium or any other medicines, I can tell you whether that dose raises any obvious concerns.
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