Quercetin and Levofloxacin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Levofloxacin
Quercetin
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced fluoroquinolone effectiveness
Interaction Deep Dive
In vitro, quercetin competitively inhibits binding to DNA gyrase by quinolone antibiotics1. Though the effect in humans is unknown, caution is advised if quercetin is taken with fluoroquinolones.
Why it happens (mechanism)
Competitive inhibition of binding to DNA gyrase by quinolone antibiotics
Literature reports
1 report — tap to read
a) In vitro, quercetin exhibited competition with 3(H) norfloxacin for binding to DNA gyrase, though at much higher concentrations than quinolone antibiotics tested. The IC50 of quercetin was 7.80 micromoles (mcmol) compared with the IC50 of traditional quinolones: levofloxacin 2.9 mcmol; ciprofloxacin 3 mcmol; ofloxacin 3.55 mcmol; norfloxacin 3.8 mcmol 1.
Common questions
Can I take Quercetin and Levofloxacin together?
Reduced fluoroquinolone effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Quercetin and Levofloxacin interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Quercetin or Levofloxacin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Hilliard JJ, Krause HM, Bernstein JA, et al: A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase. Adv Exp Med Biol 1995; 390:59-69. PubMed
Keep reading about Levofloxacin
Keep reading about Quercetin
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