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? When sunlit hours get shorter, you could have trouble getting enough vitamin D without supplements. Consequently, it is critical 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.
Prednisone Increases Vitamin D Needs:
Q. I wish you would warn people that prednisone lowers vitamin D levels. Following a kidney transplant, I need prednisone to prevent rejection. I need to take a lot more vitamin D to maintain a healthy blood level.
A. Use of corticosteroids like prednisone dramatically reduces vitamin D levels (International Journal of Environmental Research and Public Health, Jan. 2022). As a result, people on long-term prednisone should monitor their vitamin D levels on a regular basis.
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.
You can learn more about vitamin D dosing in our eGuide to Vitamin D and Optimal Health.