Research
Quercetin for Bladder Health: Evidence, Interactions and Cautions
Quercetin is an ingredient used in bladder supplements marketed to women. Below is what it has actually been studied for, how strong that evidence is, the drug interactions and cautions on record, and the primary source our grade rests on — all drawn from the HerWellReport ingredient dataset.
Also sold as: Quercetin dihydrate; quercetin glycosides
What the evidence says about Quercetin
A 2025 Frontiers in Pharmacology review of phytochemicals for interstitial cystitis found the quercetin evidence is entirely preclinical, from rodent and cell models of cyclophosphamide-induced cystitis, and cited no human trials. Neither the 2022 AUA interstitial cystitis and bladder pain syndrome guideline nor the EAU chronic pelvic pain guideline makes any statement about quercetin. Where it does appear in human bladder studies it is one of six ingredients in products such as CystoProtek, so nothing can be attributed to quercetin itself. Its poor water solubility and heavy first-pass metabolism mean oral bioavailability is low.
The grade "early" means: early — Pilot or preliminary human data only; not enough to rely on. Grades are explained in full on our methodology page.
Read the primary source this grade rests on (opens in a new tab).
Quercetin drug interactions
- CYP3A4 and CYP2C19 substrates (quercetin inhibits both enzymes in vitro
- clinical relevance unclear)
- warfarin (a case report of raised INR that normalised on stopping)
- tamoxifen and losartan (increased exposure in preclinical models)
Who should be careful with Quercetin
- Most of the interaction signal is in vitro, animal or single case reports rather than human trials, so treat it cautiously if you take a drug with a narrow therapeutic index
- no adverse effects on kidney or liver function were seen in the trials reviewed, and up to 2000 mg a day was tolerated in a COPD safety study
Read more on HerWellReport
This entry is generated from row "Quercetin" of the HerWellReport ingredient dataset (v2.1, updated 2026-09-23). The dataset is free to reuse under CC BY 4.0 — how to cite it. Ingredient evidence is not evidence for any finished product, and nothing here is medical advice.