Vitamin D + You: Not a Vitamin, and Not One Size Fits All

In truth, the ideal replacement dose of thyroid hormone can range widely from one person to another. Some people require 25 mcg per day; others require 800% greater doses. Likewise, vitamin D requirements can range widely. I have used anywhere from 1000 units per day, all the way up to 16,000 units per day before desirable blood levels were achieved.

Vitamin D dosage needs to be individualized. Factors that influence vitamin D need include body size and percent body fat (both of which increase need substantially); sex (males require, on average, 1000 units per day more than females); age (older need more); skin color (darker-skinned races require more, fairer-skinned races less); and other factors that remain ill-defined.

But these are "soft" rules. While in my office experience with 1000 patients on vitamin D the average female dose is 4000-5000 units per day, the average male dose is 6000 units per day to achieve a blood level of 60-70 ng/ml (somewhat higher than I've advocated in past), there are frequent exceptions of all stripes. I've had 98 lb women who require 12,000 units, 300 lb men who require 1000 units, 21-year olds who require 10,000 units.

Let me reiterate: Vitamin D dose needs to be individualized.

There's only one way to truly individualize your need for vitamin D and thereby determine your dose: Measure a blood level.

Nobody can gauge your vitamin D need by looking at you, nor by your skin color or other simple measurement like weight or body fat. A vitamin D blood level needs to be measured specifically─period.

Unfortunately, many people balk at this, claiming either that it's too much bother or that their doctor refused to measure it.

I would rank normalizing vitamin D as among the most important things you can do for your health. It should never be too much bother. And if your doctor refuses to at least discuss why he/she won't measure it, then it's time for a new doctor. If you're worried about adding to rising healthcare costs by adding yet another blood test, think of all the money that could be saved by sparing you from a future of cancer, heart disease, osteoporosis, diabetes, etc. The cost of a vitamin D blood test is relatively trivial (around $40-50.)

So, how much vitamin D should you take? Enough to raise your blood level of 25-hydroxy vitamin D to normal. (We aim for a normal level of 60-70 ng/ml.)

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