Is Vitamin C (High Dose ≥1000mg/day) Safe with Furosemide?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Avoid vitamin C supplementation above 500mg/day in patients with CKD or those on diuretics with reduced kidney perfusion. If supplementation is necessary, ensure adequate hydration and monitor urine oxalate and renal function.
Why this interaction occurs
High-dose vitamin C (ascorbic acid) is metabolized to oxalate, which is renally excreted. Furosemide reduces renal blood flow and urinary volume in some patients, increasing oxalate concentration in the renal tubules. In CKD patients, reduced oxalate clearance combined with high dietary oxalate load can precipitate calcium oxalate crystal deposition and acute or progressive oxalate nephropathy.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 274,011 reports mentioning Furosemide. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Furosemide + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Vitamin C (High Dose ≥1000mg/day) interactions → · All Furosemide interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.