Vitamin D calculator

How the numbers work

Vitamin D response is highly individual: the same dose raises blood levels a lot in one person and only a little in another. Body weight is one of the biggest factors, so this tool scales the dose to your weight.

• If you know your serum level: the estimate is the daily dose needed to move from your current level to your desired level, added to any supplement you already take.
• If you do not know it: the estimate is a general weight-based starting dose that assumes a typical insufficient baseline. Getting a blood test first gives a far more accurate result.
• The range: because response differs so much between people, a low-to-high range is shown around the central estimate rather than a single exact number.

The model uses a widely cited steady-state relationship, where each additional 100 IU of vitamin D per day raises blood levels by roughly 1 ng/ml (2.5 nmol/L) over time, scaled to your body weight since larger bodies generally need more. A common target range in vitamin D research is 100 to 150 nmol/L (40 to 60 ng/ml). Serum levels convert as 1 ng/ml = 2.5 nmol/L, and vitamin D amounts as 1 mcg = 40 IU.

These estimates are for educational information only. They are not medical advice and do not replace testing or guidance from your own practitioner. Vitamin D from sunlight is self-regulated by the body and is very unlikely to cause toxicity, but supplemental vitamin D can build up and become harmful at higher intakes, so higher is not better.