09/24/2026
๐๐ข๐ญ๐๐ฆ๐ข๐ง ๐๐: ๐๐๐ข๐ฅ๐ฒ ๐๐ฌ๐ฌ๐๐ง๐ญ๐ข๐๐ฅ ๐จ๐ซ ๐๐๐๐ข๐๐๐ฅ ๐๐๐ ๐๐๐จ๐ฌ๐?
Part 1 of 2: How Much Do We Actually Need?
This is the first in a two-part series taking a closer look at vitamin D3 supplementationโfrom normal daily requirements to the very high doses sometimes used in medicine.
I originally wrote about this subject some time ago. The discussion that followed, including comments about physicians using extremely high doses of vitamin D3, encouraged me to revisit the evidence and update the topic.
The question remains fascinating:
Why do standard recommendations talk about hundreds of IU per day, while some medical protocols use tens of thousands, or even more?
The answer starts with an important distinction:
Nutritional supplementation and medical treatment are not the same thing.
๐น ๐๐ก๐๐ญ ๐๐ฌ ๐๐ข๐ญ๐๐ฆ๐ข๐ง ๐๐?
Vitamin D3 (cholecalciferol) is a fat-soluble vitamin that our skin can produce following exposure to sunlight.
It plays an established role in:
โข Calcium and phosphorus absorption
โข Bone and muscle health
โข Normal immune function
โข Numerous cellular processes
Food sources include fatty fish, egg yolks and fortified foods, although sunlight and supplementation can also contribute significantly to vitamin D status.
๐น ๐๐จ๐ฐ ๐๐ฎ๐๐ก ๐๐จ ๐๐๐๐ฅ๐ญ๐ก๐ฒ ๐๐๐ฎ๐ฅ๐ญ๐ฌ ๐๐๐๐?
This is where my original post needed an important update.
The 2024 Endocrine Society guideline recommends that generally healthy adults under 75 should not routinely supplement above established dietary reference intakes solely for disease prevention.
For healthy adults, the U.S. reference intake is generally:
โข 600 IU/day for adults up to age 70
โข 800 IU/day after age 70
The guideline also does not recommend routine vitamin D blood testing in otherwise healthy adults.
Another important distinction:
4,000 IU/day is the established tolerable upper intake level for adults - it is not the recommended daily intake.
๐น ๐๐จ ๐๐ก๐ฒ ๐๐ซ๐ ๐๐ฎ๐๐ก ๐๐ข๐ ๐ก๐๐ซ ๐๐จ๐ฌ๐๐ฌ ๐๐จ๐ฆ๐๐ญ๐ข๐ฆ๐๐ฌ ๐๐ฌ๐๐?
Because medicine is different from general nutritional supplementation.
Physicians may use doses above normal nutritional recommendations when treating documented deficiency or particular medical conditions.
Some specialized protocols go considerably further and use very high doses of vitamin D, including approaches proposed for certain autoimmune conditions.
These protocols should not be confused with recommendations for healthy people.
And this leads to the much more controversial question:
What happens when we move from 600 - 800 IU per day to 20,000, 50,000, or even substantially more?
That is what I will explore in Part 2.
๐โ๐๐ ๐๐๐ ๐ก ๐๐ ๐๐๐ ๐๐๐ข๐๐๐ก๐๐๐๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ๐๐๐ก ๐๐๐๐๐ฃ๐๐๐ข๐๐ ๐๐๐๐๐๐๐ ๐๐๐ฃ๐๐๐.