Vitamin D Dosing Calculator

This calculator converts a vitamin D blood result into a daily IU dose using the common rule of thumb that roughly 100 IU per day raises serum 25(OH)D by about 1 ng/mL. It first computes your deficit — target level minus current level, floored at zero so overshooting your target never produces a negative dose — then multiplies by 100 and scales for body weight against a 70 kg reference, since heavier bodies distribute the same dose across more mass. Sun Exposure then subtracts a flat credit: 500 IU for moderate outdoor time, 1000 IU for high, on the logic that sunlight covers part of the gap; the dose is rounded to the nearest 100 IU and never drops below a 400 IU floor, so even a zero deficit returns the baseline. Two consequences worth understanding: because the dose is built proportional to the deficit itself, Months to Target barely responds to your current or target level — a bigger gap gets a proportionally bigger dose, so the projected timeline is essentially a function of body weight, floored at one month — even if your current level already meets or exceeds your target, in which case "1 month" simply means there is no real correction to make.

And the Maintenance Dose is set at 40 percent of the correction dose with a 1000 IU floor, intended to hold the level once reached rather than keep climbing. The weekly figure is just seven times the daily. Not modeled: D2 versus D3 potency, fat-malabsorption conditions, or medication interactions.