Vitamin D Update – Are 3 out of 4 Americans Really Deficient?


Six months ago, in September 2008, I wrote a post on vitamin D. Since then info keeps pouring in about the apparent benefit of this supplement. This month researchers at the University of Colorado Denver School of Medicine reported that three out of four Americans are deficient in vitamin D. They claim that’s up from about one out two 20 years ago. Some have argued that it might just seem that way because of how vitamin D was measured then and now.

After I researched and wrote that post 6 months ago, I started measuring my patients’ vitamin D levels. I am shocked at the results. You’d never guess what vitamin D levels are like here in the “Sunshine State” of Florida.

About Vitamin D

To get up to speed on vitamin D and why we care about it, first read my September 2008 post.

Measuring Vitamin D Levels

The labs my practice uses measure vitamin D in ng/ml (a measurement in grams) . The reference range I listed in my September post is in nmol/L (a measurement in moles). Rather than get all hung up in the mathematical conversions, I’m going to use the reference range in ng/ml that my labs use, because their numbers are the ones I’m going to tell you about.

For Vitamin D the reference range is 32.0 – 100.00 ng/ml.

Less than 32.0 we will consider deficient and greater than 100.0 is we will consider high. As I noted in my last post levels greater than 75 are best and that will be our goal.

  • Disclaimer: These measurements and target levels are currently being debated, studied and scrutinized by researchers and medical specialists. I am not in a position to be able to comment on the accuracy of the testing that is being done at my own labs or in labs across the country. My practice uses leading national laboratories that have contracts with the largest insurers. In writing this post I am not suggesting policy or proposing guidelines. I am simply reporting on research I read and what I observe as a clinician. My clinical opinion is based on information that is currently available. It is my opinion there may be great benefit (and so far I have uncovered no harm) in all of us knowing and trying to lift our vitamin D levels to between 75 and 100 ng/ml. OK, now back to the post.

Starting Vitamin D Levels in Florida

After I wrote my vitamin D post six months ago I started adding a 25 (OH) vitamin D level to all the routine labs I order. I have been shocked at the results.

More than 3 out or 4 of my patients have levels in the low 30s and many are even lower than that – in the 20s and down into the teens. The lowest level I have seen was reported as < 7 ng/ml. The highest level I have seen was 117 ng/mg. That was in a patient on supplemental vitamin D for the prior 6 months.

Remember, this is in the state of Florida! My own vitamin D level (and I confess to getting more sun than I should and often not wearing sunscreen when I’m only out for an hour to walk or run) was 36.4 ng/ml. If levels are borderline-low to low in Florida, then it does not seem to be just a sun issue. I really wonder what they are like in African Americans who live in New England or Alaska.

Vitamin D Supplements to Raise Blood Levels

In my practice we are supplementing our patients with Vitamin D3 at a dose of 4000 IU a day. Yes, you read right – not 400 IU – 4000 IU a day. (D3 is more metabolically active than D2.) After three months on that dose levels are only gradually going up. Vitamin D3 4000 IU/day for 3 months has brought levels in the low to mid 30s up to the low to mid 50s – still shy of our goal of 75 ng/ml.

The only dramatic rise in a vitamin D level I’ve seen so far was in one woman who started with a very low level – in the teens – misunderstood her instructions and took 8000 IU/day for three months. That dose lifted her up to the mid-60s.

How Much Vitamin D Is Enough?

The question is – what is the best dose to raise vitamin D levels to a target of greater than 75 ng/ml and then what dose will keep it there? As I have only been monitoring these levels for 6 months, I’ll have to get back to you on that. Stay tuned.

How Much Vitamin D Is Safe?

Vitamin D3 is sold in strengths of 400, 800, 1000, 2000 and 4000 IU. Doses of up to 10,000 IU/day have been given without ill effects. The prescription strength dose of vitamin D is 50,000 IU and given by mouth once weekly.

If your vitamin D level is low, 4000 IU/day seems a reasonable dose to raise your level. It is still less than the prescription strength for the week and even if you have a little extra vitamin D in your calcium supplements and multivitamin, you will not be overdosing. My patient who took 8000 IU/day suffered no ill effects. Based on the numbers I am seeing in the patients at my practice, 400 to 800 IU seems utterly inadequate to lift low vitamin D levels.

Any questions or thoughts?

This information is offered for educational purposes only and is not intended to diagnose, prescribe or treat. For that please seek direct care from a health professional.

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8 comments so far. (Post your own)

#1 | On September 25, 2009, Vicki said:

Thanks for these guidelines. I recently had my Vitamin D levels tested and my number was 29, after supplementing with about 1,000 IU for a couple months. The gradual rise you see in levels after supplementation is interesting. Here in Massachusetts, we can’t get much sun in the winter, but I wonder if you recommend more sun exposure to your patients in addition to the supplements.

I recently found a great web site on Vitamin D Deficiency here: They have a research section with all the latest articles. It’s amazing how many conditions are involved.

#2 | On September 27, 2009, Carla Mills said:

Thanks for your comment, Vicki.

After 6 to 8 months on vitamin D3 at a dose of 4000 IU/day (and I was not shy about popping a couple if I forgot one day) my level went from 36 to 85. I have now decreased my vitamin D supplements to 2000 IU/day and will recheck my levels in another 6 months.

As for sun exposure, sources I’ve read recommend 5 to 30 minutes of sun exposure without sunscreen between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back. I’ll tell you, living in Florida and loving the outdoors, I get WAY more sun than than that and I still had a vitamin D level of 36 before I started taking supplements.

Thanks, too, for another resource link.

Carla Mills, ARNP

#3 | On May 31, 2010, Sally said:

I never realized teh important role Vitamin D plays. I have a severely low blodd level of 4! I am now on week two of 50,000 iu epr week. I can already see a tremendous difference! I just turned 40 and was feeling so exhausted, moody and merely chalked it up to getting older. I feel like a new person in a mere two weeks.

#4 | On May 10, 2011, jim smith said:

ideal levels are 36-40 ng/ml according to this review:  Am J Clin Nutr. 2006 Jul;84(1):18-28.

#5 | On May 10, 2011, Carla said:

Thanks for your comment, Jim.

In this review (J. Nutr. 135:317-322, February 2005): “Several studies have more accurately defined vitamin D deficiency as circulating levels of 25(OH)D ≤ 80 nmol or 32 µg/L. Recent studies reveal that current dietary recommendations for adults are not sufficient to maintain circulating 25(OH)D levels at or above this level, especially in pregnancy and lactation.“ And, I might also note, osteopenia and osteoporosis.

Then this from the Institute of Medicine’s “Dietary Reference Intakes for Calcium and Vitamin D” released November 30, 2010: “Vitamin D measurements, or cut-points, of sufficiency and deficiency used by laboratories to report results have not been set based on rigorous scientific studies, and no central authority has determined which cut-points to use. A single individual might be deemed deficient or sufficient, depending on the laboratory where the blood is tested.“

So, for now, the IOM is recommending 4000 IU/day as the maximum recommended dose per day. Stay tuned, this is an evolving topic in medicine.

#6 | On June 08, 2011, Willa Stewart said:

IN April my vitamin D level tested at 4. Approx. 2 months later it tested at 6. This was due to the doctor prescribing the generic for DRISDOL, 50,000IU yes, 50,000IU capsules per week. Now I have added 5000IU per day. I am 66yrs old work 10 hr days, and   have a 4 hr commute by bus every day. The fatigue was killing me. I feel the difference already but I have a long ways to go.

#7 | On October 31, 2011, Ashley said:

I recently received test results via my family physician, I had a level of 29 and the nurse explained that I should be in the 31-50 range. However when I look online the rangers differ quite often. I am so confused and frustrated!! is there a type of specialists who deal with vitamin deficiencies more specifically? I am suffering with extreme fatigue, weight gain, and the list goes on. Upon taking 6,000 IU’s per day for the last week I have felt a lot of energy for about 4 hours and then a crash. Has anyone else experienced these symptoms? What has helped you? Very useful article,BTW! Thanks—

#8 | On November 20, 2011, Carla said:

Fatigue is a vague symptom that can be caused by many things. It is important when suffering from fatigue to consult with a health professional in order to run down the list of all the possible causes in your particular situation. There are many.

Here’s a link to a Fact Sheet on Vitamin D from the Office of Dietary Supplements at the national Institutes of Health. Perhaps it will provide some additional information:

Hope this helps.

Carla Mills

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