SupplementScience

Vitamin D3 — Frequently Asked Questions

DJP
Reviewed by , MD, Board Certified Internal Medicine

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Frequently Asked Questions

How much vitamin D3 should I take daily?

Most adults benefit from 1,000-4,000 IU daily. If you are deficient (serum 25(OH)D below 30 ng/mL), a healthcare provider may recommend 5,000-10,000 IU for 8-12 weeks to restore levels, followed by a maintenance dose. The optimal blood level is 40-60 ng/mL according to the Endocrine Society.

Should I take vitamin D3 with vitamin K2?

Combining D3 with K2 (specifically MK-7) is recommended for bone health. Vitamin D increases calcium absorption, while K2 activates proteins that direct calcium into bones and teeth rather than arteries. This combination may reduce the cardiovascular risk associated with calcium supplementation.

What is the difference between vitamin D2 and D3?

Vitamin D3 (cholecalciferol) is the form produced by human skin and found in animal sources. D2 (ergocalciferol) comes from plant and fungal sources. Research shows D3 is 87% more effective at raising and maintaining serum 25(OH)D levels compared to D2, making it the preferred supplement form for most people.

Can I get enough vitamin D from sunlight alone?

It depends on latitude, skin tone, age, and sun exposure. At latitudes above 37 degrees N (most of the U.S.), UVB rays are insufficient for vitamin D synthesis from November through February. People with darker skin tones require 3-6x more sun exposure. Most dermatologists recommend supplementation over relying on sun exposure due to skin cancer risk.

Full Vitamin D3 Guide

References

  1. (). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. DOI
  2. (). Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. New England Journal of Medicine. DOI
  3. (). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. British Journal of Psychiatry. DOI
  4. (). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition. DOI