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How much vitamin D is needed to achieve optimal levels?

Posted on: May 22, 2017   by  Amber Tovey


Nearly every cell in the body contains a vitamin D receptor. Research shows vitamin D plays an important role in skeletal, immune, developmental and cardiovascular health. Thus, maintaining optimal vitamin D levels is vital for overall health.

A heated debate surrounds the recommended vitamin D dosage and levels. While the Vitamin D Council recommends that adults take 5000 IU of vitamin D3 daily, the Institute of Medicine (IOM) established 4000 IU daily as the tolerable upper level of intake, meaning the highest level unlikely to cause harm in nearly all adults. On the other hand, the Endocrine Society Practice Guidelines state that up to 10,000 IU of vitamin D3 daily is safe for most adults. These conflicting recommendations can leave the public confused.

So, what’s the truth? How much vitamin D do our bodies need? How much vitamin D is too much? Researchers conducted a study in search of the answers.

A total of 3,882 participants were included in the study. The average age of the participants was 60 years old. Less than 1% of the participants were considered underweight, 35.5% had a normal BMI, 37.0% were overweight and 27.5% were obese.

At the beginning of the study, 55% of the participants reported taking vitamin D. The average dose of vitamin D increased from 2,106 IU daily at the beginning of the study to 6,767 IU daily about one year later. The average vitamin D levels increased from 34.8 ng/ml to 50.4 ng/ml during this time (p

The researchers wanted to determine the dosage needed to achieve healthy vitamin D levels, as defined by levels of 40 ng/ml or higher. They also wanted to determine the incidence of side effects, including hypercalcemia. Here is what the researchers found:

  • Change in vitamin D levels were influenced by vitamin D dosage, body mass index (BMI) and vitamin D levels at the beginning of the study.
  • Participants who were vitamin D deficient (
  • Participants without vitamin D deficiency at baseline experienced a blunted response to the same vitamin D dose compared to someone with vitamin D deficiency.
  • Response to vitamin D supplementation was less with increasing BMI. In other words, obese individuals required the greatest supplementation to achieve sufficient levels, and normal weight or underweight required the least supplementation to achieve sufficient levels.
  • Vitamin D3 intakes of at least 6,000 IU daily were required for those with a normal BMI to achieve a vitamin D status above 40 ng/ml.
  • Overweight participants required vitamin D3 intakes of at least 7,000 IU daily to achieve a vitamin D status above 40 ng/ml.
  • Obese participants required vitamin D3 intakes of at least 8,000 IU daily to achieve a vitamin D status above 40 ng/ml.
  • Average calcium levels did not differ from the beginning of the study to the end of the study.
  • A subgroup of participants (285) did not experience significant increases in vitamin D status despite reporting taking substantial intakes of vitamin D (> 4,000 IU daily). The researchers determined that gastrointestinal issues were likely attributed to the malabsorption but non-compliance undoubtedly played a role as well. (For example, the rate of non-compliance with antihypertensive medication is about 30%.)
  • Twenty new cases of hypercalcemia occurred between the beginning of the study and the end. Those with vitamin D levels below 40 ng/ml were more likely to experience hypercalcemia than those with vitamin D levels of 40 ng/ml or higher.

The researchers were also interested in whether vitamin D supplementation led to an increased incidence of hypercalciuria, high calcium levels in the urine. It is thought that excessively high vitamin D levels may cause hypercalciuria. However, the researchers found that the incidence of hypercalciuria actually declined after vitamin D supplementation, starting with a total of 67 hypercalciuric cases but at follow-up 67% were no longer hypercalciuric.

Furthermore, it’s important to point out that none of the participants developed any evidence for clinical vitamin D toxicity, which consists of hypercalcemia and 25(OH)D> 200 ng/ml, fatigue, anorexia, abdominal pain, frequent urination, irritability, excessive thirst, nausea and sometimes vomiting.

Biochemical vitamin D toxicity consists of 25(OH)D >200 ng/ml, hypercalcemia and a suppressed PTH level with no clinical symptoms, but none of the participants had that either.

Because most labs identify the normal range for 25(OH)D at 30-100 ng/ml, some physicians believe any 25(OH)D above 100 ng/ml is toxicity. It is not; it is usually just hypervitaminosis D.

The researchers concluded,

“Doses of vitamin D in excess of 6,000 IU/d were required to achieve serum 25(OH)D concentrations above 100 nmol/L [40 ng/ml], especially in individuals who were overweight or obese without any evidence of toxicity.”

One thing that the authors didn’t mention is the role genetics may play in this. For example, the gene that codes for the 25-hydroxylase has a genetically determined variation in its transcription. Some people have more 25-hydroxylase than others and thus will obtain higher 25(OH)D levels than others.

While the authors did not stress it, these subjects had repeated vitamin D levels drawn. Given these findings, keeping the genetics in mind, the only way to be sure you are > 40 ng/ml is to get a 25(OH)D test.


Tovey, A. & Cannell, JJ. How much vitamin D is needed to achieve optimal levels? The Vitamin D Council Blog & Newsletter, May 10, 2017.


Kimball, S. Mirhosseini, N. & Holick, M. Evaluation of vitamin D3 intakes up to 15,000 international units/day and serum 25-hydroxyvitamin D concentrations up to 300 nmol/L on calcium metabolism in a community setting. Dermato-Endocrinology, 2017

17 Responses to How much vitamin D is needed to achieve optimal levels?

  1. bob40151100

    This is excellent information. I have had difficulty obtaining an optimal level of D25 (for me at least) starting out at 25 and 6mos increased to 25.2 and 6mos later to 52. I want to try for 80-100. By the way my Dermatologist at last check up for pre cancerous spots stated “you look really, really good”.
    Thanks for everything you do giving the public this much needed teaching.

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    • Amber Tovey

      Hi Bob,

      Thank you so much for sharing your experience with vitamin D. I am so happy to hear that you are healthy and doing well!

      Warm regards,

      Amber Tovey

  2. blueberre

    I wanted to increase my Vitamin D through the winter months. My average was about 50 ng/mL with 2000 a day. At 5000 IU’s a day it went up to 71 ng/mL within a couple of months. I guess I’m more responsive than others, One size doesn’t fit all. I went back to my 2000 a day dose.

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    • Amber Tovey

      Hi Blueberre,

      You make an excellent point. It’s always important to remember that vitamin D is not a “one size fits all,” as you mentioned. There are so many factors associated with vitamin D status. That’s why we believe people should have their vitamin D levels tested two months after implementing a vitamin D supplementation or sun exposure regimen. This way, people can see how their bodies respond to supplementation/sun exposure.

      Thanks again for the reminder, Blueberre!


      Amber Tovey

  3. joemorgan

    I am a holistic physician. My experience with D3 shows that levels above 80 and up to 130 are best levels. I take 10,000iu daily year round. I had one patient elevate to 190 D3 level from up dosing while she had severe illness. She was talking 20,000iu daily for about a month. She had no symptoms I could discern related to D3 toxicity.
    R. Vieth PhD- paper showed of all patients with D3 intoxication were above 273. 2-3 were at that level but most showed levels of 900-1400.
    You would have to take a lot of D3 to get to those levels.
    I personally, and for my patients, try to get the D3 level to 80 or above where the immune function begins.
    Analogy: If T levels are 350 in a man with some low-T symptoms, we can raise him to 500 or 750 or higher. He will function best at his highest tolerated level- that is one without side effects.
    D3 should be given at the highest levels up to 130.

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    • tmiller4209338100

      Thank you for this info. Very helpful!

    • Ellen

      I was taking with all my supplements may be around 6500 IUs a day of D3. I got tested and I was around 1O4ng/ml. My internist was extremely worried I was close to toxicity. I felt great however. I came totally off for three weeks and my levels came down to 54ng/ml. For about six months I kept my level of intake at 800 IU. I was retested and I believe it was still normal range according to local recommendations which I believe is under 60. So I imagine this is hereditary because I over those last six months hardly saw the sun at all and was indoors most of the time. I decided to two much that I’ve read about people with multiple sclerosis which I have two of my level to 1300 for now.

    • Ellen

      I am re-submitting this because resubmitting this because my phone as usual put in things that were not what I said.) I taking with all my supplements maybe around 6500 IUs a day of D3. I got tested and I was around 1O4ng/ml. My internist was extremely worried I was close to toxicity. I felt great however, but I came totally off Vitamin D for three weeks and my levels came down to 54ng/ml. For about six months I kept my level of intake at 800 IU. I was retested and I believe it was still normal range in the high 50s according to local recommendations which I believe 40 -60. So I imagine this is hereditary because over those last six months I hardly saw the sun at all and was indoors most of the time. I decided much as I’ve read about people with multiple sclerosis needing more VIT D (and I have MS) I am taking now 1300 IU/ day.

    • gypsysoul3

      Hi, perhaps you could please explain your basis for recommending these dosages of D3. Thank you.

  4. [email protected]

    I’m early 60s, 142 lbs, BMI ~20. During the darker months of the year, 3,000 IU keeps me around 50ng/ml. (In the lighter months, my running shirtless in the sun maintains that level.) So I was a bit surprised by the study’s suggestion that most people needed so much more supplementation. But maybe I’m an outlier.

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  5. tmiller4209338100

    What a great study and summary. Thank you for publishing this!

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    • Amber Tovey

      Thank you so much, tmiller, for your feedback!



  6. [email protected]

    What about people with chronic cancer conditions such as myeloma? I take D3 at 5,000 IU/day and am typically measured 25OHD at about 40 to 60 ng/mL.

    It seems to me that someone who is immune compromised as I am because of disease even with therapy, that taking D3 daily can only help in keeping me as healthy as possible.

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  7. JOEL_WS

    I have been mega-dosing D3 along with vitamin K2 MK-7 at levels from 50,000 IU to 100,000 IU currently for over a year always with K2 from 300 to 600 mcg. My calcium levels are upper normal. The level checks are always limited to “greater than 96 ng/mL” due to limitations of lab equipment. From my limited research, there is little to worry about and the levels may be restorative and a number around 100 is said to be cancer preventative as vitamin D has been shown to induce cell death (apoptosis) in cancer cells while supporting normal cells. I can’t say that these doses have had any positive benefits regarding previously diagnosed ailments (hypothyroidism) but can say it hasn’t seemed to cause or make worse any other complaints either. I’m 54 and at 5’9″ usually weigh in at around 150lbs. I tend to agree with those who say it would take a LOT of D to harm yourself. You do need to have adequate levels of K2 as well because it stimulates a protein that regulates free calcium out of the bloodstream (where it can damage heart valves and other things) and into the bones where it belongs. I think the medical community has been somewhat misled about the dangers of vitamin D, probably because it prevents many things the doctors want to treat.

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    • JOEL_WS

      Just to clarify, the amounts I listed are per day.

  8. dgreg19089579100

    I have been taken vit.d3 for a year at 5000iu along with MK-7 vitamin k-2 100 mcg and a serum level of d3 60 ng/mole and serum PT INR of 0.91. My calcium kevel in between the range.

    After that I have incresed the k2 to 200mcg a day with the same d3 dosage, my INR decreased to 0.84. I know vitamin k thickness the blood and since then I have dropped to 100 mcg of k2. In couple of months I will be checking my INR again. Anybody had similar experiences with k2 and INR?

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  9. HannahMC

    Thanks for this! Will you be changing your daily recommendations (5,000IU daily) in light of this study?

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