NutriStack
What is happening. Tenofovir disoproxil is eliminated renally and can cause nephrotoxicity, including a Fanconi-like proximal tubulopathy, in susceptible patients. Chronic high-dose vitamin C (typically several grams daily) increases urinary oxalate excretion and is an independent risk factor for kidney stones and can add oxidative/oxalate burden to the kidney. In a patient already at some risk of tenofovir-related renal injury, habitual megadose vitamin C is an avoidable additional renal stressor. Ordinary dietary or low supplemental doses of vitamin C are not a meaningful concern.
Mechanism. High-dose vitamin C is metabolized to oxalate, increasing urinary oxalate and stone risk; combined with TDF's potential for renal tubular injury this represents additive renal stress rather than a direct pharmacokinetic interaction.
Recommendation. Avoid chronic high-dose vitamin C (gram-level daily supplements) while on TDF, especially with any history of kidney stones, reduced eGFR, or signs of tubular dysfunction. Standard dietary intake and typical multivitamin amounts are fine. Maintain good hydration and keep up routine renal monitoring (creatinine, eGFR, urinalysis for proteinuria and glucosuria) during tenofovir therapy.