“Most people should take vitamin D.”
Moderate confidence because current endocrine guidance suggests that healthy adults younger than 75 generally do not benefit from vitamin D above the recommended dietary intake, and large trials found no reduction in cancer, cardiovascular events or fractures in generally healthy, mostly sufficient adults. Some groups and diagnosed conditions do warrant supplementation.
Most healthy adults under 75 do not need vitamin D above the recommended daily intake to prevent disease. Supplementation is appropriate for diagnosed deficiency and some life stages or risk groups.
Vitamin D prevents rickets and osteomalacia, but benefits for other outcomes do not automatically extend to already sufficient people. Current guidance supports empiric supplementation above the usual intake for children, pregnancy, adults over 75 and some adults with high-risk prediabetes, while optimal doses remain uncertain.
Vitamin D is important, but high doses are not automatically better and can be harmful.
Safety note: Excess vitamin D can cause high calcium, kidney stones, kidney injury, confusion or abnormal heart rhythm. High-dose intermittent regimens are not a harmless shortcut, and vitamin D can interact with some medicines.
Talk to a healthcare professional if: Ask about testing or treatment if you have bone disease, low calcium, malabsorption, kidney or liver disease, prior bariatric surgery, take medicines that alter vitamin D metabolism, or have another established indication. Routine blood screening is not recommended for healthy adults without an indication.
Meet the recommended intake through food and, if needed, a standard supplement. More is not better, and routine high-dose supplementation or testing is not supported for every healthy adult.
Check your total intake from food and supplements. Use a clinician-guided plan if you have a condition or life stage that changes your need.
Similar claims on Vitamin D
If you get little sun or are older, a modest daily vitamin D is reasonable, cheap insurance - but it's not a cure-all, and topping up when you're already fine won't help.