Can too much Vitamin C and D be a bad thing?

Can too much Vitamin C and D be a bad thing?

We are in the midst of a global pandemic from COVID-19. Apart from social distancing and masks, many people are looking into how they can reduce their chances of getting the disease and if they do get the disease how they can reduce the symptoms and severity.

There has been much interest in the use of supplements to try and meet this demand. A good friend and colleague of mine Dr Mantu Gupta has written about 2 supplements in common use to reduce the severity of COVID-19. I have summarized the report below.

Vitamin C
There have been a number of studies to suggest that Vitamin C at doses over 200mg/day reduces the severity of the common cold. Furthermore, some studies suggested that high doses of vitamin C in critically ill patients from infections may improve outcomes. Of course, this has not been proven in COVID-19 but there are ongoing studies. In the mean time many people are taking what is called a ‘megadose’ of vitamin C where more than 1000 mg/day is consumed. Unfortunately, excess Vitamin C is converted to oxalate in the urine. This oxalate is the primary component of most of the kidney stones that we encounter. This can lead to increased risk of forming kidney stones especially in people who have had kidney stones before.
I suggest that if someone wants to take Vitamin C, then limit it to not more that 500mg/day. You would potentially have the benefits while minimizing the risk of kidney stones.

Vitamin D
Vitamin D has been shown to reduce the risk of acute respiratory infections. In COVID-19 patients, those with lower vitamin D levels were more likely to have higher viral loads and more likely to die from the virus. Unfortunately, once again too much of a good thing may be bad for us. Many studies have shown that high levels of Vitamin D supplementation has been associated with increased calcium in the urine. Calcium once again is the main component of many kidney stones. This is especially so if patients take doses of more the 4000IU/day. I suggest that if you are taking vitamin D supplements, do keep it in the 2000IU/day range so that you can reap some of the benefits of Vitamin D while minimizing your risk of stones.

In a nutshell, Vitamin C and D may have protective effects on COVID-19 but should be taken in moderation to reduce your chances of forming stones. More importantly, they should be taken with adequate fluids to reduce your risk of stone formation.


Khusid JA, Atallah WM, Kyprianou N, Gupta M. What Stone-formers Should Know About Vitamin C and D Supplementation in the COVID-19 Era. Eur Urol Open Sci. 2020;21:9-11. doi:10.1016/j.euros.2020.07.006