People who are interested in keeping their immune system functioning well–and who isn’t, these days–know that vitamin D is critical. But how can you make sure that your level of the sunshine vitamin is high enough, especially as fall is shortening sunlit hours in the northern hemisphere? One place to start is to find out whether your medicines suppress your vitamin D without you realizing it.

Do Medicines Suppress Your Vitamin D?

Q. I recently read that it is important to maintain adequate levels of vitamin D to help prevent severe infection from the coronavirus. This might be a good time for people to check with their doctors to find out if any of their medications might be suppressing vitamin D levels.

I take prednisone to prevent organ transplant rejection. My doctor has recommended high doses of vitamin D to maintain my levels between 40 and 50 ng/mL.

Evidence from Iran:

A. Thank you for this recommendation. There is evidence to suggest that when vitamin D levels are “sufficient” that people are better able to recover from COVID-19 (PLOS ONE, Sept. 25, 2020). In this study from Tehran, the mortality rate of hospitalized COVID-19 patients differed based on vitamin D levels. To be precise, 9.7 percent of COVID-19 patients with 25-hydroxy vitamin D levels over 30 ng/mL died.  However, when levels were below 30 ng/mL, the mortality rate was 20 percent. The investigators defined 30 ng/mL as adequate.

Evidence from Israel:

Israeli research suggests that adequate vitamin D levels may even reduce the risk of catching the coronavirus (medRxiv, Sept. 7, 2020). This study really relies on the strength in numbers, since it includes the health records of 4.6 million people. As a result, it bolsters the argument that vitamin D is essential for optimal immune function.

Which Medicines Suppress Your Vitamin D Levels?

First, corticosteroids such as prednisone or dexamethasone can indeed lead to lower levels of vitamin D in the body (Journal of Clinical Endocrinology and Metabolism, Dec. 2011). In addition, anti-epileptic drugs such as phenytoin or carbamazepine, medicines used against breast cancer such as taxol and tamoxifen and HIV agents like ritonavir and saquinavir also reduce circulating vitamin D (Dermatoendocrinology, April 1, 2012). Even herbs such as St. John’s wort (Hypericum perforatum) and Kava kava (Piper methysticum), like these medicines, suppress your vitamin D levels. Moreover, the blood pressure pills spironolactone and nifedipine can also have this effect. Finally, antimicrobials including clotrimazole and rifampicin lower vitamin D. 

Learn More:

You can learn more about vitamin D dosing in our eGuide to Vitamin D and Optimal Health

Related People's Pharmacy Health Guide

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