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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Does vitamin D affect my medication or does my medication affect my vitamin D?

The vitamin D supplement business has grown from sales of 75 million dollars in 2006 to 550 million in 2010. More and more, the question arises: does vitamin D affect my medication or does my medication affect my vitamin D? The 25-hydroxylase (CYP3A4) which converts vitamin D to 25(OH)D, is also an enzyme that metabolizes many drugs. Test tube studies indicate that as many of half of all therapeutic drugs are metabolized by CYP3A4, suggesting that vitamin D may have widespread effects on many drugs.

Recently Dr Kim Robien and colleagues of the University of Minnesota conducted a thorough review of the world’s literature. They identified 1225 reports to select 109 unique reports that met their quality hurdles to report on the subject.

Robien K, Oppeneer SJ, Kelly JA, Hamilton-Reeves JM. Drug-Vitamin D Interactions: A Systematic Review of the Literature. Nutr Clin Pract. 2013 Jan 10.

On drugs that affect vitamin D, they found the following:

  • The bile acid sequestrates Celestipo (trade names Colestid, Cholestabyl) and cholestyramine (Questran, Questran Light, Cholybar) could theoretically reduce vitamin D levels by interfering with intestinal absorption, but no study confirms that they do so.
  • Orlistat (Xenical) decreases vitamin D levels by binding the pancreatic enzymes involved in absorbing fats and vitamin D is a fat-soluble vitamin.
  • Statins increase vitamin D levels substantially.
  • The TB drugs, rifampin and isoniazid, may decrease vitamin D levels and the authors, noting vitamin D may help treat TB, recommend that those on such drugs get their vitamin D levels checked.
  • Hydroxychloroquine (Plaquenil) is used to treat malaria and lupus. It may reduce vitamin D levels.
  • Antiepileptic drugs, such as phenobarbital, phenytoin, primadone, carbamazepine, oxcarbazepine, and felbumate, may lower vitamin D levels. Forty-six studies addressed this question but the authors were unable to find any good study of this effect.
  • Steroids may lower vitamin D levels, but the authors were not convinced by the data. Certainly, patients on steroids have low 25(OH)D levels and osteoporosis but the authors could not say that was due to the direct effect of steroids on vitamin D levels.
  • Immunosuppressants, like cyclosporine (Sandimmune) and tacrolimus (Prograf, Advagraf, Protopic) do not appear to alter vitamin D status.
  • Chemotherapy agents used in cancer treatment do not appear to affect vitamin D levels, but the authors recommend that anyone on chemotherapy get their level checked.
  • Highly active antiretroviral agents (HAART) may lower levels.

On the other hand, they found the following on vitamin D’s effect on specific drugs:

  • Thiazides diuretics [such as Dyazide, chlorothiazide, hydrochlorothiazide (Microzide), Indapamide and metolazone (Zaroxolyn)], which are used to treat hypertension, probably do not affect serum calcium levels on those taking vitamin D. Only three case reports suggest thiazides and vitamin D may raise serum calcium and those case reports all had another possible cause of the hypercalcemia.

The authors conclude that little is actually known about vitamin D‘s interactions with drugs and caution is in order. They conclude,

“The area of drug–vitamin D interactions is a clear example of a situation where lack of evidence does not equate to ‘no harm.’ The available research to date has primarily focused on drugs that are commonly associated with osteoporosis (suggesting a potential effect on vitamin D metabolism) or where case reports of adverse outcomes have been reported in the medical literature. Given the increasing prevalence of vitamin D supplementation in the general population, continued evaluation of potential drug–vitamin D interactions is warranted.”

Furthermore, they recommend:

“Until further research is available, healthcare professionals should be aware of the potential for drug–vitamin D interactions, assess their clients’ use of dietary supplements, and monitor serum 25(OH)D concentrations where indicated with the ultimate goal of achieving adequate serum 25(OH)D concentrations while optimizing drug efficacy and minimizing drug toxicity.”

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

6 Responses to Does vitamin D affect my medication or does my medication affect my vitamin D?

  1. D-fiant says:

    I have difficulty with the comment above that Chemo drugs don’t affect Vit D.

    My son is getting chemo and while supplimenting at about 5,000iu/day he went from about 120 (Aust) (48 USA) to 55 (Aust) (22 USA).

    He increased his intake to 10,000 / day in a period of about 6 weeks. (Early December 2012 in QLD Australia – hot summer to mid January 2013) Of which half of the time he was out of hospital he got a lot of sun. In the other 3 weeks he had a B cycle lymphoma hyper CVAD chemo treatment.

    In this 6 week period he only went from 55 Aust (22 USA) to 61 Aust (24.4 USA) I suggest that the increase was restrained by chemo.

    I also add this reference and an extract.


    A big story, an EXTRACT for your convenience = “Conclusion: Chemotherapy is associated with a significant increase in the risk of severe vitamin D deficiency. Patients with colorectal cancer, especially those receiving chemotherapy, should be considered for aggressive vitamin D replacement strategies.”

    There are a number of case studies where VitD improved Radiation treatment.




  2. Rita and Misty says:


    I’ve attached one of my favorite journal articles on Vitamin D and cancer treatment. It is from the Journal of Cancer, 2010; 1:101-107:

    Vitamin D in combination cancer treatment

    Yingyu Ma, Donald L. Trump and Candace S. Johnson


    Taken from the article:

    “Numerous epidemiological and preclinical studies support a role of vitamin D compounds in cancer prevention and treatment in colorectal, breast, prostate,

    ovarian, bladder, lung and skin cancers and leukemia (1, 5, 6). Low levels of plasma 25(OH)D3 are associated with higher cancer incidence and mortality in men in colorectal, breast, lung and prostate cancers (7-10). The broad spectrum anti-tumor effects of calcitriol and analogs are mostly based on inhibition of cancer cell proliferation and invasiveness, induction of differentiation and apoptosis, and promotion of


    The article goes on to speak to how Calcitriol has been studied in various combination treatments and shown to have synergistic or additive antitumor activities….

    I am so sorry to hear about your son’s ill health, and you both will be in my thoughts.

    Kindest regards,

    Rita Celone Umile

  3. D-fiant says:

    Further to my post above I should have added this link:


    “Vitamin D3 and vitamin D3 analogues as an adjunct to cancer chemo-therapy and radiotherapy”

    This says that Vit D also works with Chemo to kill cancer.

    But as shown in my first post – it appears that the chemo process depletes Vit D – thus the importance of replacing lost Vit D when getting chemo.

  4. Rita and Misty says:

    @D-fiant, I encourage you to take a few minutes and read the link I attached for you….it speaks to exactly what you are discussing…I think it will point you in further directions.

    Sending good thoughts your way,


  5. Brian McLean says:

    I find it a sad testimony by the medical community, that despite all its pharmacological “research” it remains essentially in ignorance about the interaction between their drugs and Vitamin D. The only explanation I can imagine for this situation is the mindset that cavalierly dismisses the significance of “vitamins” beyond the notion that “if you don’t have a deficiency disease, then all is well.” They ought to feel shame, but I reckon they do not.

  6. Rita and Misty says:


    I certainly feel your pain, as I am constantly banging up against the “brick wall” of the main stream medical community when it comes to Vitamin D, as well as other nutritional supplements.

    But, I do realize that these physicians were taught in medical school to dismiss nutritional, and to be extremely cautious of Vitamin D….

    Yes, research now indicates Vitamin D (as well as other supplements) holds MUCH promise for treatment and prevention of so many of our modern day diseases….

    However, it has been my experience that the RESEARCHER and the GP rarely talk….so there is no consensus…and yes, the PATIENT suffers….


    Rather than place negative labels on physicians, whom I choose to believe are basically good people, trying their best to help save lives, I think we in the Vitamin D Community might take a more assertive (and perhaps unique) tact: TALK to your PHYSICIAN as if s/he were your friend…discuss the journal articles and studies that support Vitamin D…attempt to educate him/her…BUT, if your efforts and pleas go UNMET…then SEARCH OUT a more receptive doctor….INTERVIEW for your new doctor…be choosy…be selective…after all, it is YOUR LIFE. And, if you must part from your current physician, be certain to POLITELY inform him/her as to the reasons behind your decision.

    The BEST doctors I’ve ever had the pleasure of working with on my health, were doctors who appreciated me and accepted me on equal ground.

    It is ALL about the LEARNING…and we learn from each other!

    Best regards,

    Rita Celone Umile