Enter your measured 25 hydroxy vitamin D level. The tool applies the common rule that about 100 IU daily raises the level by 1 ng/mL, aiming for 40.
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Fill in the form and press Calculate. You will get your number, an interpretation chip, and a personalized chart pack drawn instantly in your browser.
- Risk spectrum with your position marked
- Reference ranges from the original publication
- Shareable link, nothing stored
Scientific references
The rule of thumb
Each 100 IU of daily vitamin D3 raises serum 25OH D by roughly 1 ng/mL over two to three months in average adults. Multiplying the gap to 40 ng/mL by 100 gives a repletion estimate.
Understanding your result
- Zero means you are at or above the 40 ng/mL target
- Up to 2000 IU is a moderate everyday repletion range
- Higher estimates deserve clinician supervision and follow up testing
Why the target is 40
Expert groups debate 20 versus 30 versus 40. Forty ng/mL sits at the generous end favored by many researchers for immune and muscle function, while remaining far below toxicity.
After repletion
Recheck after three months, then maintain with a lower daily dose, usually 1000 to 2000 IU depending on sun exposure.