Vitamin D Repletion Calculator

How it is calculated

The tool reads your blood 25-hydroxyvitamin D level in ng/mL and picks a fixed loading plan from cut-offs. Below 20 ng/mL it gives 50,000 IU once a week for 8 weeks, and from 20 up to but not including 30 ng/mL for 6 weeks. From 30 up to 99.9 ng/mL it returns zero doses with the note "level sufficient, no loading"; from 100 ng/mL upward it returns zero with a note to seek medical advice. Total dose is weekly dose × weeks. The weekly dose and duration never change with body weight, age or the exact level within a band. A level of 0 or below, or above 1000, shows no result. This is a reference regimen, not a prescription.

Common mistakes

• Entering the level in nmol/L, the unit many labs outside the United States use. The field takes ng/mL, and since 1 ng/mL is roughly 2.5 nmol/L, a value of 50 nmol/L is about 20 ng/mL, not 50.
• Expecting a higher weekly dose for a lower level. The weekly dose is fixed at 50,000 IU and every level below 20 gets the same 8-week course, so severe deficiency still needs a clinician's judgement.
• Treating the result as a prescription. It is a general loading template, and the weekly total may be unsuitable for people with certain conditions or medicines.
• Reading "no loading" as proof the level is ideal. Everything from 30 to 99.9 gets the same answer, and from 100 the tool tells you to seek medical advice instead of giving a dose.
• Forgetting the retest and the maintenance step. The plan ends after 6 or 8 weeks, and what comes next depends on a repeat blood test.