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Vitamin D Daily Dose Calculator
Get a personalized daily vitamin D3 dose recommendation. Anchored to Holick 2011 (Endocrine Society Clinical Practice Guideline), Heaney 2003 (dose-response), Drincic 2012 (BMI adjustment). Test-first protocol.
Quick answer
The Endocrine Society Clinical Practice Guideline (Holick 2011) recommends 1,500-2,000 IU/day for most healthy adults to reach the sufficiency target of serum 25(OH)D ≥30 ng/mL. Heaney 2003 demonstrated each 100 IU/day raises serum 25(OH)D by ~1 ng/mL in deficient adults. Higher BMI requires 1.5-2x the dose (Drincic 2012); darker skin and minimal sun exposure both increase the requirement. The calculator below personalizes your dose based on your inputs.
Vitamin D Daily Dose Calculator
Estimates an evidence-based daily vitamin D3 dose anchored to Holick 2011 (Endocrine Society Clinical Practice Guideline), Heaney 2003 (dose-response), and Drincic 2012 (BMI adjustment). Informational only — not medical advice. Test serum 25(OH)D and discuss with your doctor before dosing >2,000 IU/day.
To raise serum 25(OH)D from 25 to 40 ng/mL, you need approximately 15 ng/mL increase × 100 IU/day per ng/mL (Heaney 2003).
Re-test serum 25(OH)D after 12 weeks to verify you've reached 40 ng/mL.
Next steps
- Take vitamin D3 (cholecalciferol, NOT D2) with the largest fat-containing meal — Mulligan & Licata 2010 showed 32-50% better absorption
- Re-test serum 25(OH)D in 12 weeks; adjust dose to hit your target range
- If you're severely deficient (<20 ng/mL), discuss the 50,000 IU weekly repletion protocol with your doctor (Pilz 2019)
- For the full timing + form-selection protocol, see our vitamin D timing guide
Show methodology + sources
- Holick et al. 2011 (Endocrine Society Clinical Practice Guideline): target serum 25(OH)D ≥30 ng/mL for sufficiency, 50-80 ng/mL optimal range
- Heaney et al. 2003 (Am J Clin Nutr): each 100 IU/day raises serum 25(OH)D by ~1 ng/mL in deficient adults; underpins the gap-based dosing formula
- Drincic et al. 2012 (Obesity): obese adults require 2-3x the dose of normal-BMI adults to reach equivalent serum levels; underpins the BMI multiplier
- Vieth 1999 (Am J Clin Nutr): safety review establishing 4,000 IU/day as a conservative UL for self-supplementation
- Pilz et al. 2019 (Front Endocrinol): modern dosing protocols — daily preferred over bolus; 50,000 IU weekly bolus acceptable for documented deficiency under medical guidance
- Mulligan & Licata 2010 (J Bone Miner Res): 32% higher absorption when taken with fat-containing meal vs. empty stomach
- Geleijnse et al. 2004 (J Nutr): K2 (menaquinone) intake associated with reduced coronary calcification at higher D doses
Limitations: This is a population-level estimate. Individual response varies due to absorption efficiency, VDR receptor polymorphisms, and competing nutrient interactions. Always confirm with serum testing.
Why testing matters more than the calculator
Vitamin D status varies 5-10x between adults — same supplement dose, different blood levels. The calculator gives a starting point, but the only way to optimize is to measure serum 25-hydroxyvitamin D and dose toward a target.
The right test: 25(OH)D (storage form), NOT 1,25(OH)2D (active hormone). The active form is tightly homeostatically controlled and tells you little about reserves. Cost: $40-80 direct-to-consumer at LabCorp or Quest. Often covered by insurance with a doctor's order.
For the full dose-form-timing protocol (D3 not D2, with fat-containing meal, AM not PM), see our vitamin D timing guide and dose-by-status guide.
FAQ — Vitamin D Dosing
Quick answer
D3 (cholecalciferol) raises serum 25(OH)D approximately 3x more effectively per IU than D2 (ergocalciferol), per Heaney 2011 (J Clin Endocrinol Metab). Unless you're strictly avoiding lanolin/animal-derived ingredients, D3 is the right choice. Vegan D3 from lichen exists and matches the efficacy of standard D3.
Quick answer
Yes, but the toxicity threshold is high. The IOM Tolerable Upper Intake Level is 4,000 IU/day for self-supplementation. Vieth 1999 reviewed acute toxicity data and found no documented toxicity below 10,000 IU/day. The 50,000 IU weekly repletion protocol (averaging ~7,000 IU/day) stays under physician supervision. If serum 25(OH)D climbs above 100 ng/mL, reduce dose.
Quick answer
At doses above 2,000 IU/day, K2 (specifically MK-7 menaquinone at 90-180 mcg/day) is a research-supported pairing. Vitamin D upregulates calcium absorption; K2 helps direct that calcium to bone rather than arterial walls. Geleijnse 2004 (J Nutr) demonstrated that higher K2 intake associates with reduced coronary calcification. The D+K2 stack is well-tolerated and commonly co-formulated.
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