A streamlined stack of supplements designed to meet your most critical needs - Adapt Naturals is now live. Learn more

The Role of Vitamin D Deficiency in Thyroid Disorders


Last updated on

Digital Vision/Digital Vision/Thinkstock

This article is part of a special report on Thyroid Disorders. To see the other articles in this series, click here.

Note: This will be my last post until the end of August. My wife and I are going up to the Sierras to hike and soak in the hot springs for a few days before the big acupuncture licensing exam next Tuesday. The day after that we head to southern Mexico to surf and relax on the beach for a couple of weeks.

I won’t have time to respond to comments while I’m away, but please do leave them and I’ll answer when I come back. I’ve got a few more articles in the thyroid series, and next up after that will be type 2 diabetes & metabolic syndrome. Have a great August!

Vitamin D is all the rage. It seems like every day another article is published in medical journals or the mainstream press about the dangers of vitamin D deficiency, and the benefits of supplementation. In this article we’re going to discuss the impacts of vitamin D on thyroid physiology and wade into the increasingly murky topic of vitamin D supplementation – specifically as it relates to thyroid disorders.

Vitamin D deficiency has been associated with numerous autoimmune diseases in the scientific literature. Vitamin D plays an important role in balancing the Th1 (cell-mediated) and Th2 (humoral) arms of the immune system. It does this by influencing T-regulatory (Th3) cells, which govern the expression and differentiation of Th1 and Th2 cells.

Vitamin D deficiency is also specifically associated with autoimmune thyroid disease (AITD), and has been shown to benefit autoimmune-mediated thyroid dysfunction.

Vitamin D has another little-known role. It regulates insulin secretion and sensitivity and balances blood sugar. This recent paper showed that vitamin D deficiency is associated with insulin resistance. And as we saw in a previous article, insulin resistance and dysglyemcia adversely affect thyroid physiology in several ways.

“Okay, big deal,” you say. “I’ll just take vitamin D supplements or get more sun.”

Not so fast. Research over the past two decades has identified a variety of mechanisms that reduce the absorption, production and biologic activity of vitamin D in the body.

  • Since vitamin D is absorbed in the small intestine, a leaky and inflamed GI tract – which is extremely common in people with low thyroid function – reduces the absorption of vitamin D.
  • High cortisol levels (caused by stress or medications like steroids) are associated with lower vitamin D levels. They synthesis of active vitamin D from sunlight depends on cholesterol. Stress hormones are also made from cholesterol. When the body is in an active stress response, most of the cholesterol is used to make cortisol and not enough is left over for vitamin D production.
  • Obesity reduces the biologic activity of vitamin D. Obese people have lower serum levels of vitamin D because it gets taken up by fat cells.
  • Not eating enough fat or not digesting fat properly reduces absorption of vitamin D. Vitamin D is a fat-soluble vitamin, which means it requires fat to be absorbed. People on low-fat diets, and people with conditions that impair fat absorption (like IBS, IBD, gall bladder or liver disease) are more likely to have low levels of vitamin D.
  • A variety of drugs reduce absorption or biologic activity of vitamin D. Unfortunately, these include drugs that are among the most popular and frequently prescribed – including antacids, replacement hormones, corticosteroids, anticoagulants and blood thinners.
  • Aging reduces the conversion of sunlight to vitamin D becomes.
  • Inflammation of any type reduces the utilization of vitamin D.

“Okay, fine,” you say. “I’ll just get my vitamin D measured, and if it’s low, I’ll take supplements.”

If only it were that simple. We now know that certain people with normal serum levels of vitamin D still suffer from deficiency symptoms. How is this possible?

In order for circulating vitamin D to perform its functions, it must first activate the vitamin D receptor (VDR). The problem is that many people with autoimmune disease have a genetic polymorphism that affects the expression and activation of the VDR and thus reduces the biologic activity of vitamin D. Studies have shown that a significant number of patients with autoimmune Hashimoto’s disease have VDR polymorphisms.

In plain English, here’s what this means: if you have low thyroid function, you might be experiencing vitamin D deficiency even if your blood levels of vitamin D are normal. It also means that, if you have a VDR polymorphism, it’s likely you’ll need to have higher than normal blood levels of vitamin D to avoid the effects of vitamin D deficiency.

Like what you’re reading? Get my free newsletter, recipes, eBooks, product recommendations, and more!

“Okay, I get it,” you say. “I may need higher vitamin D levels than the average person if I have one of those genetic defects. So tell me what my levels should be!”

Well, this is where we venture into murky territory. The question of how high vitamin D levels should be is very difficult to answer in the case of someone with autoimmune thyroid disease. Studies suggest the optimal 25(OH)D level is 35 ng/mL for the average person. Some researchers (notably Dr. John Cannell and colleagues at the Vitamin D Council) have suggested that 50 ng/mL should be the minimum level.

The bulk of the evidence, however, doesn’t support that claim. For starters, the other authors of the study Dr. Cannell used as the basis for his 50 ng/mL recommendation came to a very different conclusion from the same data. In the paper they published in the American Journal of Clinical Nutrition, they wrote that their data confirmed the previously acknowledged optimal level of 35 ng/mL – not the 50 ng/mL suggested by Dr. Cannell.

What’s more, some recent studies have shown that higher isn’t better when it comes to vitamin D. A study in the American Journal of Medicine found that, in most people, maximum bone density occurs at 25(OH)D levels between 32-40 ng/mL. When levels are pushed above 45 ng/mL, as recommended by Dr. Cannell, bone density starts to decrease. Another study published in the European Journal of Epidemiology found that South Indians 25(OH)D levels above 89 ng/mL were three times more likely to have suffered from heart disease than those with lower levels.

If you’ve been following this blog for a while, you know that we don’t put too much faith in epidemiological studies. They don’t prove causation. They only show a relationship between two variables. But the relationship of vitamin D to calcium levels also provides a plausible mechanism by which high 25(OH)D levels could increase the risk of heart disease.

Complicating the matter further, recent work by researcher Chris Masterjohn suggests that the harmful effects of vitamin D toxicity are at least in part caused by a corresponding deficiency in vitamins A & K2. The fat-soluble vitamins A, D & K2 work synergistically, as Masterjohn has described in his Cod Liver Oil Debate article and a recently published scientific paper.

Masterjohn’s hypothesis, which has been confirmed by others, raises the possibility that the higher levels of 25(OH)D that were linked with lower bone density and heart disease may be safe if vitamin A & K2 levels are sufficient. Unfortunately, there is no clinical evidence (that I’m aware of) that helps us to answer this question.

“Okay, okay,” you say. “Just tell me how much to take already!”

I wish it were easier to answer this question. Really, I do. I think about it a lot for my own patients.

The research is clear that 35 ng/mL is the minimum level for optimum function for healthy people. But people with autoimmune thyroid conditions aren’t healthy.

They often have GI disorders, inflammation, stress, excess weight, VDR polymorphisms and other factors that impair their production, absorption and utilization of vitamin D. This suggests that the minimum 25(OH)D level for those with AITD may be significantly higher than for healthy people.

My current approach with these patients is to do a cautious trial of raising their serum levels to a range of 60-70 ng/mL. If their symptoms improve at this level, I will then switch them to a maintenance dose while watching for clinical signs of vitamin D toxicity. These include kidney stones (also a sign of vitamin K2 deficiency), low appetite, nausea, vomiting, thirst, excessive urination, weakness and nervousness. I will also monitor serum calcium levels, because elevated calcium in the blood is a sign of vitamin D toxicity and a significant risk factor for cardiovascular disease (especially in the presence of vitamin K2 deficiency). Calcium levels above 11-12 mg/dL (or 2.8-3 mmol/L) are indicative of vitamin D toxicity.

I will also make sure these patients are getting adequate amounts of vitamin K2 and vitamin A in their diets. Sources of vitamin A include organ meats, cod liver oil and full-fat milk and cream from grass-fed cows. Sources of vitamin K2 include fermented foods like natto, hard cheeses and kefir as well as egg yolks and butter from grass-fed cows. I may also use a vitamin K2 supplement (MK-4/MK-7 combo) if patients can’t tolerate fermented foods.

Finally, if you’re interested in finding out if you have a VDR polymorphism that could be affecting your metabolism of vitamin D, Genova Diagnostics has an Osteogenomics panel that tests for them. I’m not sure how much value this test has clinically, however, since it doesn’t provide any information about how the VDR polymorphism affects vitamin D metabolism in each specific case. That’s still something that would have to be figured out using the “trial and error” process I described above.

In time we can hope that the explosion of research being conducted on vitamin D will lead to more clarity on the question of appropriate serum 25(OH)D levels for people with autoimmune diseases. For now, we have to make our best guess based on clinical results and anecdotal reports.

ADAPT Naturals logo

Better supplementation. Fewer supplements.

Close the nutrient gap to feel and perform your best. 

A daily stack of supplements designed to meet your most critical needs.

Chris Kresser in kitchen


Join the conversation

  1. The nd/ml measurements are the desired blood levels.  IU measurements refer to supplementation.  The reason I haven’t given a specific recommendation is that the amount you supplement with depends on your current levels.  It doesn’t make any sense to recommend that “everyone” take 10,000 IU.  Vitamin D can be toxic when blood levels rise above 85 – 100 ng/ml, especially in the presence of K2 and A deficiency.  I suggest people maintain levels of approx. 40-60 ng/ml.  If you’re low, you can use 6-10,000 IU to bring your levels up, but you have to test to confirm and to make sure you don’t go to high.  After that, generally 2,000 IU is good for maintenance.

    • Great article, Chris. Okay, so here is my question (and feel free to email me if you can, so I get your reply). I had, at age 24 a bunch of autoimmune thyroid stuff and had my thyroid removed. I am now in my mid thirties and have been on thyroid replacement since, without incident. I’d say, “feeling great”, except I do have other weird symptoms, though they kind of existed pre-thyroid.

      For instance, I’ve been gluten free since I was 24, but still struggle with candida (only as a white tongue) when having more sugar. I have chronic digestive issues. My endoscopy was perfect, so I suspect I have gastroparesis. I only realized this after suffering for a while, especially the last few years. I have all the symptoms of gastroparesis but just don’t want to have that icky radioactive test. Still, the slow digestion affects what I can eat (greatly, I’m not good with most of the foods I ate before- and healthy stuff… like brussels sprouts don’t digest… so my try at veganism utterly failed).

      Currently, I’ve had off and on muscle twitches (but they seem related to digestive trouble) for several years. Sometimes they are gone for months and months, other times happen a lot. It seems to be, as I said, in sync with my tummy not digesting. I have times when I fall asleep and feel my dreams begin too quickly, before I’m fully asleep (hypnagogic speech- began when I was anemic eight months ago, while trying to be vegan). I also have times when my food doesn’t digest (or maybe when I have too many carbs/ sugars, though my blood sugar test -not the glucose, the other one- shows I’m okay). When my food doesn’t digest I get other neuro symptoms too- numb chin, until the acid subsides, etc. Occasionally I get small, sporadic hives from eating foods- but all IgE tests show normal.

      The freakiest thing is that since my digestion got bad I can feel my brain get cluttered at certain points, which is new. Kind of like it’s not fully awake, mainly when I’m tired or hungry but it’s freaky. It feels most like intrusive thought OCD, but comes and goes only when the food I eat doesn’t digest. For instance, if my food comes up (as it often does with gastroparesis, in the evening) then I don’t seem to have that brain stuff happen. When my food stays down but doesn’t digest, I get the cluttered brain and ocd sensation. It typically goes away with rest or when my food comes up.

      How does this relate? I suspect I’m deficient in vitamins, but modern medicine (Western variety) doesn’t oft check on such stuff or look into levels per person (what we might need opposed to the norm). Is 1000 mg of Vit D. good? Should I have more? Also, someone told me that people who have had autoimmune issues shouldn’t take Vitamin D… that it only helps BEFORE they have autoimmune issues.

      Anyway, I’m in California. Any suggestions you have on Vitamin D or anything would be great. Thanks.

  2. I’m really confused on how much Vitamin D supplement to take. Your article uses a ng/ml unit of measure but every Vit D supplement I’ve seen is listed in IU measurements. I have been taking 2,000 IU’s a day but recently heard a news report that 10,000 is now being recommended. This time of year adequate sunlight is not available here as we sometimes have weeks with nothing but cloud cover and fresh fish is not readily available. So Vit D softgels are what I rely on. How much should one be taking?

  3. Chris-
    I just subscribed, thanks to this article. I don’t know if I am technically hypothyroid, but none of my medical tests are extreme enough to indicate anything. I am desperate, so I figured the more information the better…so thanks. I have low Vitamin D, high LDL, slightly high cortisol, bottom of ‘normal’ T3, T4, but relatively ‘normal’ TSH. They had me on Vit D supplementation, but my levels went up really, really slowly (though they are now at 25). I now take 2000-4000IU a day to keep them there. I do take ‘Rainbow Light Women’s One’ which has A and K supplementation as well.

    I’ve essentially felt like hell ever since my daughter was born 5 years ago, but particularly bad the last 5 months (low energy, weakness, joint pain, numbness, whole hand and foot pain, etc). I feel like I am 90, despite being an athlete, non-smoker, non-drinker, vegetable lover my whole life. It’s just so confusing and severe that I can’t believe that they can’t figure it out. I hope to piece it together with the assistance of some of your excellent research/analysis.
    thanks again.

    • Ur info u posted bout health issiues ur having..blew my mind…I could have written it..really sorry ur having these problems hate to admit that glad I’m not alone..wish the best for u…thank u

  4. Re vitamin D levels obtained through sunlight – this review shows that levels reached in a variety of studies – farmers, surfers 105 – 163nmol/L
    Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety
    Also uptake appears to be related to genetic differences.
    Common genetic determinants of vitamin D insufficiency: a genome-wide association study
    By the way – I’m really enjoying your series on Hashimotos – I was diagnosed last year when I had a general check-up. Slightly high TSH, follow up anti-body test showed they were very high.

    • Interesting enough ~ 165nmol/L (66ng/mL) is the middle of the normal range, at least, in the US. When I had Vitamin D toxicity issues last year I noticed my Vitamin D level approached that level and seemed to level out after stopping intake for several months.

      I wouldn’t be surprised if ~ 165nmol/L is optimal, assuming optimal intakes of Vitamin A and K2 as well.

  5. @chris
    you say “Their levels don’t rise above 80 ng/mL.”
    well, 80ng x 2.5 = 200nmol. i was stating 120-50nmol is usual in “sunny” people acording to several studies. so where’s the problem?
    fyi: the unit ng/L is pretty much meaningless outside the US, as it actually doesn’t make much sense to measure the concentration of molecules in a fluid as its mass. that’s about the same as asking for 350g of eggs in the supermarket. of course, as usual, the US thinks holding on to ridiculously outdated and illogical units is somehow cool..

  6. “Complicating the matter further, recent work by researcher Chris Masterjohn suggests that the harmful effects of vitamin D toxicity are at least in part caused by a corresponding deficiency in vitamins A & K2.”
    I’ve been saying for some time that vitamin A should become the next vitamin superstar.  I believe I experienced subclinical vitamin A deficiency and that it affected my reproductive health and also the fetal development of my daughter.  She was born with vesicourinary reflux bilaterally (in plain English, her urine sometimes ran up into her kidneys on both sides) which was diagnosed at age four months.  They tried telling me it was genetic.  I believed it for a while.  Then I ran across a WAPF paper stating that vitamin A is necessary in fetal kidney development.
    And then I found these.
    Sorry about the bizarre font size changes, your comment software apparently uses rich text instead of plain.
    But yes.  This is serious.  There are people walking around with blood pressure and kidney problems.  There are women struggling with bad menstrual symptoms and infertility.  And it might all have been preventable.

  7. Chris,

    Great article.  I have greatly benefited frm taking Vitamin D supplements . I was beginning to think that more is better as long as you keep your level below 100ng/mL. I have pushed my level to approx 90mg/mL and am concerned. I have reduced my dosage of Vit D3 to bring my level down. Probably what has happened is I reduced grain comsumption greatly and no wheat consumption at all and this has caused my increased levels.  Basically I don’t need as much! Fortunately I don’t supplement large doses of Calcium, about 300mg a day.
    Is the half life of supplemented Vit D3 about 3 to 4 weeks? 
    Is the half life of Vit D3 produced from UVB rays about 6 to 8 weeks? 

  8. I have been trying to unravel all the things that have been going on in my body for about 11yrs now. And you have hit the nail on the head with all the problems I have had.
    The doctors tell me you have this wrong and that, but never have they tried to teach me how to deal with it or to put it all together. Thank you so much for taking the time and effort to
    put this out there so I can see how it all lines up!

    Now I will print this and take it and a few other pages you have here and give them to my new doctor. Who at least seems to want to help me!

  9. Chris, I hope you and your wife enjoy your vacation. I just came back from a week at the beach. Hopefully, my D came up from the 42 last month. I suppose the question when sunning is – where do we draw the line between risking sun cancer and maintaining D levels? I unintentionally burned a few times on my trip. Hopefully, the D was worth it. I will say that I had lots more energy last week. I, personally, always feel better after getting out in the sun. I have been detoxifying my gut and I’ve remained GF for the past six months. Hopefully, that will help with D absorption. My real problem now is not Hashimoto’s, as the antibody attacks have all stopped, but my adrenals are still in poor shape. My doc is treating the adrenals with natural supplements, so it takes longer than the HC route.
    Thanks again for a great article and for drawing the connection between adrenals and vitamin D as well. This article is definitely a keeper.
    🙂 Tamra

    • Hi everyone,

      As Kim said, and as the article outlined, sunlight is sufficient for healthy people under 40, but may not be for those over 40 with inflammation and other conditions.

      Qualia, I’m not sure where you got those numbers. Here’s a figure from a study looking at young healthy people in Hawaii with more than 15 hours a week of sun exposure. Their levels don’t rise above 80 ng/mL. In that same study (the one Kim is referring to), some of those people who spent that long in the sun were vitamin D deficient.

    • Tamra, you mentioned, you detoxify your gut; how do you do it? I’m gaining wisdom from this blog since I began researching the web for gluten influences on thyroid. I stopped eating wheat, felt better for a while, but every time I eat something, I feel slightly to very tired or sleepy (I usually do not overeat) and it makes me think it is my weak gut. Any thoughts on how to strengthen it? Also, can swollen feet and face be a sign of vit D overdose/sensitivity/intolerance? I stopped taking D, and swelling/water retention is gone. thanks for your input

      • Oh my
        I had to cut off all my rings a couple of months ago. I had been taking vit d and K2 daily for 5 months. I have had problems with it before at 4000 iu a day. So, I was only taking 1000 so it was gradual and I didn’t realise the swollen fingers and feet were that. I also was having bad anxiety and very sore red gritty dry eyes. These things have gone since I had to stop supplementing nearly 3 weeks ago for tests which got held up. I tested extremely low in D last year so I was hoping the lower dose wouldn’t effect me badly. I am at a loss what to do to get up my levels. I breathe better when I am on D but cannot tolerate the other effects.

  10. You can’t depend on the sun to get optimal Vit. D levels since the majority of those suffering from thyroid conditions do NOT convert UV light efficiently into Vit. D. I recall a study done in Hawaii of people who spent at least 11 hours per week in the sun with no sunscreen. Of those tested, over half were still Vit. D deficient.  However, I think the jury is still out on the best way to supplement this w/o causing toxicity. There’s a lot of conflicting views.

  11. why try to find and define “a new” optimal D level in complicated ways when we just can measure the levels of healthy, young individuals around the globe that get plenty of sun each day (“beach guard” or farmer example)?
    just look what they have and aim for a similar level. and afaik that’s around 120-150nmol? what’s wrong with that?

  12. Thanks, Tyler.  I am concerned about the increasingly common recommendations being made to take up to 10,000 IU (or more) of vitamin D without any consideration of A & K2 status. The unintentional effect of this could be an increase in heart disease due to hypercalcemia.

    I’m especially concerned about that because many people who are supplementing with vitamin D are also taking calcium supplements.  That combination could be very dangerous.

    Jenny Ruhl, author of Diabetes Update, wrote a good article on this recently.  She started having issues when she boosted her 25D level from 39 to the upper 50s.  She did some research and found out that calcium levels in the normal upper range have been associated with increased risk of heart disease.


    • You say that higher D levels are associated with more cardiovascular disease — perhaps this is not because high D causes CVD — but rather most people with high D levels are consuming foods that are naturally high in Vitamin D — like organ meats and fortified Dairy products — and diets high in animal foods have been shown to increase the risk for CVD…perhaps that explains the association?

    • I am taking at about 10,000 units of D3 every day. I take 1200MG of calcium, 100MCG of K2 for every 1000 units D3 and around 800 -1200MG magnesium and a table spoon of cod liver oil. My D was test at the end of last Sept at 25ng/ml. I have not been tested since but wil be soon. Some of the muscle ache and weakness is gone and I had been taking adrenal supplements which helped. I ran out of the adrenal supplements and felt so much better I did not buy more. Within one week my muscles started aching again in my legs, my heart feels like it’s pounding, anxiety, feeling of shortness of breath. I started taking the adrena supps again two days ago. I can eat like crazy and not gain any weight. When I first started feeling bad I had been a little overweight and then the weight just rolled off. Does my supplement combination sound correct to you as far as the amount of each one to each other? I tried to find how much to take of all together and found different answers. I also read that adrenal exhaustion is frequent with low D. What do you think and thanks for the help. Judy

  13. This is a great article. I like how you don’t follow suit of most others and just recommend high undefined levels of D without covering the roles of other factors and co-factors. Just the other day Dr Davis covered a post on a patient with D deficiency and getting their levels to 60/70 ng/ml on 10,000 IU a day without explaining any co-factor roles of K2 and A. I possibly see some issues of everyone jumping on the D bandwagon regardless of healthy diet practices or analyzing their situation and need in depth.

  14. Alisa: for healthy people under the age of 40, sunlight and fatty fish are best.  For people over 40 and/or those with autoimmune disorders, inflammation, obesity and gut problems, a combination of sunlight, fatty fish and supplementation is probably best.

  15. Good article, Chris. I just got Dr. Kharzzian’s book on thyroid disorders and he goes into a lot of detail about this and all the other issues that cause/effect thyroid, etc. It’s actually pretty complicated but he is right in assesing thyroid problems as auto-immune in nature. The problem for most people is that they’re not getting the correct blood tests to determine what’s wrong.

    I always look forward to your writings and hope you have a great vacation!

  16. Oh wow, this (as usual) is a much more complicated medical issue than we like to hope for.

    I haven’t seen any studies pertaining to this, and am curious on your opinion. Do you think naturally obtaining Vit D via the sun is optimal, or do you think supplements are just as good? I have always thought the natural process of obtaining vits and minerals is best (via food, sun, etc.) just from a logical standpoint, but does it really matter?

    • I live in the desert and also have hypothyroidism. I had a vitamin d3 level of 16, which constitutes a severe deficiency. As I said I live in the desert, I do not normally wear sunscreen and I was tested at the height of summer. It is therefore reasonable to assume that sun exposure is not enough for e, and I have been told by my endo to take 5000IU’s every day, I have yet to be tested again. My mom has has hashimoto’s, and she indicated that in the past that her vitamin d levels have also been low. I can only assume there is a direct connection between thyroid disorders and vitamin d that can not be corrected by sunlight. I was told that my body it not converting it to it’s useable form. I think that intestinal issues relating to vitamin d3 absorption may be associated with the difficulty some thyroid patients experience with gluten. Therefore, perhaps correcting intestinal issues coupled with adequate sunlight may reduce the need for supplementation of vitamin d. But that is just a theory.


        The most vitamin D is produced on the trunk of the body, not the face.

      • New research has shown that direct sunlight is the best source but the vitamin D is produced on the skin. Your body needs 48 hours to fully absorb that vitamin D on the surface of your skin. So if you shower after sun exposure, you effectively wipe away the vitamin d on your skin. Also, if you get sun filtered through a window, most windows block UVB rays, which is the rays that produce vitamin D and let in UVA rays only. Because of our man made life style we have to compensate for so many factors that normally wouldn’t have to worry about in a natural life style closer to nature….making life more and more complicated.

        • Khalil,

          So if Vitamin D takes 48 hours to be absorbed, and presumably everyone should get a daily dose of sun for Vitamin D production, then when are we supposed to shower? I am NOT going on Naked and Afraid just to try out a more natural lifestyle.

  17. I’m aware of Holick’s opinion.  Unfortunately, there are studies that demonstrate decreasing bone density as levels increase above 45 ng/mL.  I do suspect that this is probably more a problem with K2 & A deficiency than it is too much D, but the point is that this is controversial stuff.  I personally wouldn’t be comfortable recommending levels above 80-90 ng/mL for any significant length of time.

  18. According to Michael Holick

    Vitamin D intoxication doesn’t happen until around 300 ng/ml, and that even at 10,000 IU a day, this will not cause vitamin d intoxication.  The kidney’s apparently do a good job at regulating *activated* vitamin d 1,25(OH)2 in the blood.
    Personally, I’ve been doing 4000 IU a day, every day for a year.  When I tested a year ago  (Canary Club)  I was at 19ng/ml.. I’ll be testing later this month to see the results!

    • Everyone is different and in my case Vitamin D ‘intoxication’ happens at much lower levels.

      I got the symptoms of Vitamin D toxicity at only 109ng. Somewhat later I found out I had a very low blood manganese level, which appears to be exacerbated by Vitamin D. At 10,000 IU/day, even 50mg manganese a day is not sufficient to normalize my blood manganese level. I’ve since dropped back to 5,000 IU/day to see if that helps improve the situation.

      • Hi Chris,

        Do you have some sort of reference regarding manganese and vitamin D interactions?
        Thanks in advance.