Vitamin C and kidney stones have a genuinely awkward relationship, and it is easy to misread. The vitamin itself is not the villain — the dose and the source are. A widely cited analysis from the Health Professionals Follow-Up Study (HPFS) gives the clearest number, and it is worth reading carefully before you toss your supplements or, on the other side, assume you can ignore them.
Taylor and colleagues followed 45,619 men with no history of stones for 14 years. Men whose total vitamin C intake reached 1,000 mg or more per day had a multivariate relative risk of 1.41 for forming a stone, compared with men taking under 90 mg a day. That is a 41% higher risk, and the trend across intake levels was statistically significant. The association held for supplemental vitamin C specifically and appeared in men, not women, in the parallel Nurses' Health Study cohorts.
The mechanism is straightforward. The body converts part of an ascorbic acid dose into oxalate, which then leaves through the urine. Urinary oxalate is a core ingredient of calcium oxalate stones — the most common stone type. At the modest amounts in food, this conversion is negligible. At the gram-scale doses found in many supplements, the extra oxalate can tip the balance in someone who is already prone to stones.
Getting vitamin C from food means getting it alongside water, fiber, and low oxalate. Here are common sources and their lab-measured oxalate:
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Orange, fresh | 14 mg | 1 medium | Safe |
| Strawberries, fresh or frozen | 20 mg | 1/2 cup | Safe |
| Bell pepper, raw | 1 mg | 1/2 cup | Safe |
| Broccoli, raw | 6 mg | 1 cup sliced | Safe |
| Kiwi, fresh | 1 mg | 1 medium | Safe |
Every one of these lands in the Safe zone for oxalate while supplying meaningful vitamin C. The contrast with a 1,000 mg pill could not be sharper: the pill delivers a dose the food never would, and it does so without the fiber and water that blunt oxalate's effect.
If you have a history of calcium oxalate stones, the evidence points in one direction: get vitamin C from food, and keep any supplement well under the gram-a-day mark unless a doctor directs otherwise. If you are taking a supplement for a specific reason, mention the stone history to whoever prescribed it. The risk is real but concentrated in a narrow window — high doses in men — not in a glass of orange juice.
See how oxalate values are measured and verified on our data methodology page.