Doctor warns that overuse of vitamin C supplements can drive the risk of kidney stones: ‘Can raise urinary uric acid…’

Casually taking vitamin C supplements to supercharge your immunity? Dr Sood highlights the risk factors of vitamin C supplement overuse.

Popping vitamin C tablets every time you feel run-down might seem harmless - even healthy - but overdoing it can actually backfire. While vitamin C is vital for immunity and repair, excessive supplementation can disrupt your body’s balance and lead to complications such as kidney stones. Many people overlook how differently the body handles synthetic versus food-based vitamin C, assuming “more” means “better.”

Dr Kunal Sood, an anesthesiologist and interventional pain medicine physician, is highlighting the risks of overuse and why moderation and the right source matter far more than megadoses. In an Instagram video posted on October 26, the physician explains how the body processes vitamin C and highlights that excessive supplementation can increase the risk of kidney stones.

Excess vitamin C can backfire

Dr Sood highlights that while vitamin C is essential for immune function, megadoses cannot “supercharge” your immunity and raises the risk of kidney stones. He explains how vitamin C is absorbed by the body - “Vitamin C (ascorbic acid) breaks down into oxalate, which increases urinary oxalate levels. When this combines with calcium in the urine, calcium oxalate crystals can form - the most common type of kidney stone.”

The risk is higher in men, people with a history of kidney stones and those with impaired kidney function.

What research suggests

Dr Sood points out that studies indicate an increased risk of kidney stones only with excessive use of artificial vitamin C supplements, whereas natural, food-based sources pose no such risk. He states, “In a cohort of over 1,97,000 adults followed for more than a decade, men who took more than or equal to 700 to 800 mg of supplemental vitamin C per day had a higher kidney stone risk, with the strongest signal above 1,000 mg per day. Food-based vitamin C showed no such risk. Metabolic studies found one to two grams of vitamin C per day raised urinary oxalate by 20 to 60 percent, promoting stone formation even in healthy individuals.”

Immune support versus overuse

The physician states, “The NIH notes that vitamin C supports normal immune function, but evidence for illness prevention is limited. High-dose supplements can also raise urinary uric acid and oxalate without proven added benefit.”

He recommends aiming for 75 to 90 mg of vitamin C per day from foods like citrus fruits, berries, pepper, and cruciferous vegetables - these support immunity without increasing the risk of stones. He also cautions against using long-term doses of 1,000 mg or more per day, unless specifically instructed by your doctor. As for high risk individuals, he advises, “For those with a history of stones, kidney disease, or high-dose use, consider a 24-hour urine check and emphasise hydration, normal calcium intake, and sodium moderation.”

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. It is based on user-generated content from social media. HT.com has not independently verified the claims and does not endorse them.