How Much Vitamin D Should You Take Daily?
Vitamin D matters for bone health and immune function alike, but with more time spent indoors and widespread sunscreen use, low blood levels are common. Enter your current 25(OH)D level from a recent blood test along with your target level to get an approximate daily supplement dose needed to close the gap.
A commonly used rule of thumb is that about 100 IU of daily vitamin D raises blood levels by roughly 1 ng/mL, and this calculator uses that same rule. For example, if your current level is 15 ng/mL and your target is 30 ng/mL, the 15 ng/mL gap multiplied by 100 IU works out to roughly 1,500 IU per day.
Since the tolerable upper intake level for adults is generally set at 4,000 IU per day, any calculated dose above that is capped at the limit in the result. After starting supplementation, getting a follow-up blood test in about 8-12 weeks to confirm you've reached your target - and adjusting the dose if needed - is the safest approach. If you have an underlying health condition or need a higher dose, talk to a doctor first.
Frequently Asked Questions
No. Taking too much can cause side effects like high blood calcium, so it's safest to stay within the tolerable upper intake level (4,000 IU/day for adults) and confirm your level with periodic blood tests.
Foods like salmon and egg yolks contain vitamin D, but it's hard to get enough from diet alone, so most people combine food with supplements and sun exposure.