NutriStack
Glyburide and Quercetin, a caution.
Quercetin inhibits CYP2C9 in human studies. Glyburide is metabolized by CYP2C9 (and CYP3A4) and is the longest-acting US sulfonylurea with the highest hypoglycemia risk in its class. Concentrated quercetin supplements can raise glyburide exposure and prolong its hypoglycemic effect, particularly in older adults and patients with renal impairment.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Quercetin inhibits CYP2C9 in human studies. Glyburide is metabolized by CYP2C9 (and CYP3A4) and is the longest-acting US sulfonylurea with the highest hypoglycemia risk in its class. Concentrated quercetin supplements can raise glyburide exposure and prolong its hypoglycemic effect, particularly in older adults and patients with renal impairment.
Mechanism. Quercetin inhibits CYP2C9 (and to a lesser extent CYP3A4), the primary enzymes metabolizing glyburide. Inhibition raises plasma drug concentrations. Glyburide's active metabolites accumulate in renal impairment, further prolonging the hypoglycemic window.
Recommendation. Avoid concentrated quercetin supplements (>500 mg/day) on glyburide unless your prescriber agrees. Dietary quercetin from foods is generally fine. If you take a supplement, monitor fasting and bedtime glucose for the first 4 weeks and discuss whether glyburide should be reduced.
Sources (2)
- Bedada SK, Neerati P. Evaluation of the effect of quercetin treatment on CYP2C9 enzyme activity of diclofenac in healthy human volunteers. Phytother Res. 2018;32(2):305-311. PMID 29168292
- Si D, Wang Y, Zhou YH, et al. Mechanism of CYP2C9 inhibition by flavones and flavonols. Drug Metab Dispos. 2009;37(3):629-634. PMID 19074529
Stack Score
How this pair moves the number.
Effect on the composite score
If both Glyburide and Quercetin are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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