Can vitamin C supplements lead to kidney stones?

Kidney stones occur when waste products build up and form clumps in the kidneys, leading to severe pain and difficulty in urination.
One factor that can 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 a daily requirement of 75 mg for women and 90 mg for men, increasing to 120 mg during pregnancy. While the upper limit for supplementation is set at 2000 mg per day, the relationship between high doses of vitamin C and kidney stones has garnered attention,” said Dr B. Vijay Kiran, Senior Consultant Nephrologist, Asian Institute of Nephrology and Urology, Siliguri.

Dietary sources of vitamin C, such as fruits and vegetables, are generally safe and may even help prevent kidney stones. (Photo: Getty Images)

The vitamin C you get from food sources is generally safe and unlikely to contribute to this risk. However, taking vitamin C supplements, like ascorbic acid tablets, could increase the likelihood of developing kidney stones.
Dr Kiran quoted a meta-analysis which indicated that men taking high doses of vitamin C (250-1499 mg daily) showed an increased risk of developing kidney stones, particularly with doses around 1000 mg.
Interestingly, doses between 500-1000 mg and those exceeding 1500 mg per day didn’t show the same risk, though the reasons for this are still unclear.
Despite potential benefits, megadoses 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 should limit their vitamin C intake from supplements to no more than 2,000 mg per day. Staying within this range can help protect your kidneys and lower the chances of stone formation.