Kidney stones occur when waste materials accumulate in the kidneys and form lumps, causing severe pain and difficulty in urinating.

One factor that may increase the risk of kidney stones, particularly calcium oxalate stones, is high doses of vitamin C. When consumed in large amounts, vitamin C is partially broken down into oxalate, which can combine with calcium to form crystals, potentially leading to kidney stones.

Dietary sources of vitamin C, such as fruits and vegetables, are generally safe and may even help prevent kidney stones. However, concerns arise with vitamin C supplements.

“Vitamin C or ascorbic acid is an essential nutrient, with the daily requirement being 75 mg for women and 90 mg for men, which increases to 120 mg during pregnancy. Though the upper limit of supplementation has been set at 2000 mg per day, the link between high doses of vitamin C and kidney stones has attracted attention,” said Dr B Vijay Kiran, senior consultant nephrologist at the Siliguri-based Asian Institute of Nephrology and Urology.

Vitamin C from food sources is generally safe and unlikely to contribute to this risk. However, taking vitamin C supplements, such as ascorbic acid tablets, may increase your risk of developing kidney stones.

Dr. Kiran cited a meta-analysis that showed men taking high doses of vitamin C (250-1499 mg daily) had an increased risk of developing kidney stones, especially at doses around 1000 mg.

Interestingly, doses between 500–1000 mg and above 1500 mg daily did not appear to pose a similar risk, although the reasons for this are still unclear.

Despite the potential benefits, large doses of vitamin C, especially through intravenous administration, pose risks that may outweigh their benefits.

To reduce the risk of kidney stones, the National Institutes of Health (NIH) recommends that adults consume no more than 2,000 mg of vitamin C per day from supplements. Staying within this limit can protect your kidneys and reduce your chances of forming stones.