Serum Level vs Intake Charts

One of the most common questions we receive at GrassrootsHealth after an individual has tested their vitamin D is “How much vitamin D should I take to get my levels up?”

Based on a plot of 25(OH)D values as a function of reported vitamin D intake amounts for 7,324 D*action participants, a calculation was produced to estimate the additional daily vitamin D intake needed for 90% of adults to reach a chosen target 25(OH)D serum level (age 18 years and older, weighing an average of 150 lbs).  The charts referenced here can be used as a tool to calculate how much additional supplemental vitamin D is needed to get 90% of individuals from an initial vitamin D serum level to a desired vitamin D serum level.

intake change for serum level

Example: With a starting serum level of 20 ng/ml an additional intake of approximately 5,000 IU/day would be sufficient for 90% of adults (age 18 years and older, weighing 150 lbs) to achieve a serum level of at least 40 ng/ml (100 nmol/L).

Four versions of this chart are available in the download:

  • Change in Serum Level Based on Intake (IU/day) for 90% of Adults – these charts show calculations based on an average weight of 150 lbs
    • Available in ng/ml and nmol/L
  • Change in Serum Level Based on Intake (IU/lb and IU/kg) for 90% of Adults – these charts show how to calculate using an individual’s weight
    • ng/ml and nmol/L


You may also use our D*calculator for the same calculations based on weight, starting serum level, and target serum level.


Format: PDF

Dimensions: 11 x 8.5 inches

Pages: 4