The Study
A case report of renal oxalosis and secondary hyperoxaluria due to chronic high vitamin C consumption
This story is about one person who took a lot of vitamin C pills and then their kidneys got worse. It doesn't prove the pills caused the problem—maybe something else did. It just shows one example of what *might* happen.
Analysis score
Maximum 30 for a case report.
Where the score came from
This story is about a man with weak kidneys who took a lot of vitamin C pills every day, and his kidneys got worse because the vitamin turned into a harmful substance called oxalate.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 530 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — even though vitamin C is healthy in small amounts, taking too much (over 1 g/day) when your kidneys are already weak can cause lasting damage.
- 2He took 2–3 grams of vitamin C daily; his urine had 45 mg of oxalate (normal is up to 40 mg); kidney biopsy showed crystals; after stopping vitamin C, his kidney function improved.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical Nephrology. Case Studies
Year
2025
Authors
I. Neofytou, Georgios Lioulios, Emmanouil Almaliotis, Dimitra-Vasilia Daikidou, Aikaterini Mplatsa, Elias Minasidis
Related Content
Claims (6)
In people with chronic kidney disease, taking high-dose vitamin C supplements (1 gram or more daily) results in increased oxalate in the urine and calcium oxalate crystals forming in the kidneys, which leads to worsening kidney function.
In people with chronic kidney disease, taking high doses of vitamin C (2–3 grams or more per day) leads to increased oxalate in the urine and the formation of calcium oxalate crystals in the kidneys.
Taking high doses of vitamin C (1 gram or more per day) can lead to kidney damage in people with chronic kidney disease by increasing oxalate buildup, and this risk is often missed because doctors do not routinely ask about vitamin C supplement use.
When kidney damage from excessive vitamin C intake is detected early and vitamin C is stopped, kidney function can improve with dietary changes and medication.
In people with chronic kidney disease, taking high doses of vitamin C (1 gram or more per day) leads to higher levels of oxalate in the kidneys, which can cause oxalate deposits and kidney damage.
When the body breaks down too much vitamin C, it produces oxalate that forms crystals in the kidneys and damages kidney tissue.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.