Measuring Vitamin D Levels in Your Blood

From the September 2005 edition of Dr. Fuhrman's Healthy Times:

Assessment of vitamin D status is usually made by measuring 25-hydroxy-vitamin D; however, the optimal serum concentration is somewhat controversial. The data sheets from most blood laboratories list 20 ng/ml as the cutoff for vitamin D deficiency. However, recent studies have demonstrated that parathyroid hormone (PTH) levels begin to rise as 25-hydroxy-vitamin D falls below 30, and recently there has been a growing consensus that 30 ng/ml should be used as a cutoff for the diagnosis of vitamin D inadequacy. As pointed out by T. Colin Campbell, Ph.D., in The China Study, it may be true that vegetarians and those eating little animal protein have a more efficient conversion of the 25-hydroxy-vitamin D into its biologically active form, 1,25-dihydroxy, and perhaps a blood level below 30 is not so bad in a vegan or vegetarian. I do not think there is enough evidence to take a chance with running a D level below 20, unless your level of 1,25-dihydroxyvitamin D comes out on the blood test above 40. Otherwise, I think a blood level of at least 25 ng/ml is still advisable in those who consume little or no animal products.

Recently, a large study assessed the vitamin D status of postmenopausal women receiving therapy to treat or prevent osteoporosis. Amazingly, they found that 52 percent of the 1,536 women had inadequate vitamin D levels—and these were women being treated with drugs for osteoporosis. We know that vitamin D levels are inadequate in the vast majority of American women, and that this deficiency is a major cause of disability and death.

For more on vitamin D, check out these previous posts:

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Comments (3) Read through and enter the discussion with the form at the end
Judy Lavigne - January 18, 2008 11:38 AM

Wondering what a healthy Vitamin D level is for a woman 60yrs.

Joel Fuhrman, MD - January 19, 2008 4:20 PM


Vit D 25, Hydroxy should be between 30 and 70.

Brenda - January 19, 2012 3:38 PM

My spouse has a Ca++ of 11.3 and PTH >200.
(Male, 65yoa, looks 56, no other medical problems).

MD is saying it's likely due to his conversion to plant-based nutrition (ie no dairy intake). We have followed the Eat to Live guidelines VERY closely for the past 11 months.
How do we respond to this MD if/when she advocates return to dairy products for calcium? (She told us Ca++ supplements are now linked with CV disease) Dexa and 24h urine pending.
Thank you!

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