Vitamin C is one of the major nutrients we recommend to patients who have started to lose kidney function. As a supplement, it is protective in so many ways. (See this article for more information.) There is a misconception that you can’t take vitamin C if you are at risk of kidney stones. This myth arose out of an assumption that has largely been discredited by research. Vitamin C is one of the most studied nutrients and is backed by the highest volume of clinical trials. We have an overwhelming body of evidence that vitamin C is highly safe for general use and for those with kidney damage. Large-scale human trials conducted over 14+ years demonstrated that vitamin C does not increase kidney stones. In our extensive research, we have yet to see a study that shows vitamin C causes kidney stones. In fact, some studies suggest that vitamin C may actually decrease kidney stones. We would only err on the side of caution in using vitamin C if you have very high oxalates and compromised liver function. Even then, we would recommend vitamin C immediately after getting your liver function back up.