NutriDex

The Supplement Research Compendium
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Quercetin

Plant flavonoid with a modest, dose-dependent blood-pressure effect.

Moderate evidence ⏳Longevity🛡️Gut & Immune

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
8 verified / 8
Classification
Longevity
❝
What the evidence says. Graded moderate: meta-analyses of RCTs consistently show a small systolic-BP drop (~3 mmHg, mostly at ≥500 mg/day), but effects on inflammation, blood sugar and lipids are largely null or confined to subgroups, and the headline immune claim failed in the largest trial. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)

What is Quercetin?

Quercetin is a longevity supplement used for modestly lower blood pressure. NutriDex grades the human evidence as Moderate. Quercetin is a flavonoid found in onions, apples, tea and capers, sold as an antioxidant, anti-inflammatory and immune supplement. The most reproducible human finding is blood pressure: pooled RCTs report a systolic reduction of about 1.9–3.0 mmHg, seen mainly at doses ≥500 mg/day. A small crossover trial found 500 mg/day lowered plasma uric acid by ~26 µmol/L in pre-hyperuricaemic men. Effects on C-reactive protein are inconsistent—null overall but significant in people with established disease or at high doses. Meta-analyses generally find no effect on lipids, and only subgroup (≥500 mg, ≥8 weeks) effects on fasting glucose. The popular cold/immune claim is weak: a 1,002-person community trial found no reduction in respiratory infections, with benefit limited to smaller exercise-stressed groups. Most trials are short (4–12 weeks) and bioavailability is poor, so real-world benefits are likely small.

Purported Benefits

✓Modestly lower blood pressure
✓Lower CRP in inflamed/diseased groups
✓Lower uric acid
✓Antioxidant flavonoid support

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Lower systolic blood pressureMeta-analyses show ~1.9-3 mmHg SBP drop, mainly at >=500 mg/day; small effect, no DBP change. Moderate ↑ benefit · small 2
Lower C-reactive proteinOne meta-analysis found -0.33 mg/L; another null overall, benefit only in diseased/high-dose subgroups. Mixed ↔ mixed · small 2
Lower uric acidSingle small crossover RCT (n=22) cut plasma urate ~26 umol/L in pre-hyperuricaemic men. Preliminary ↑ benefit · moderate 1
Blood lipids (LDL/HDL/TG)Meta-analyses find no effect on LDL, HDL or triglycerides. Moderate — no effect · negligible 2
Prevent respiratory infectionsLarge RCT (n=1002) found no reduction in URI rate/severity/duration overall. Moderate — no effect · negligible 1
Fasting glucose / insulin resistanceNo overall effect on FPG or HOMA-IR; FPG fell only at >=500 mg/day for >=8 wk. Mixed ↔ mixed · small 2

Dosing & Compounds

Typical Dose
500–1000 mg/day of quercetin (often as aglycone or phytosome/isoquercetin for absorption); the BP and uric-acid signals appear at ≥500 mg/day.
Active Compounds
Quercetin aglyconeQuercetin glycosides (e.g. isoquercetin, rutin)

Safety & Cautions

Oral quercetin is generally well tolerated up to ~1000 mg/day for several weeks; reported effects are mild (headache, tingling, GI upset), and high-dose or IV use has been linked to kidney toxicity. As a CYP3A4/CYP2C9 and P-glycoprotein inhibitor it can raise levels of drugs with narrow therapeutic windows—warfarin and other anticoagulants, cyclosporine and some statins—and may add to the glucose- and BP-lowering effects of antidiabetic and antihypertensive medication. Long-term safety data are lacking; avoid high doses in pregnancy, breastfeeding, and kidney disease, and separate from medications if you take CYP3A4 substrates. Educational only — always check with your doctor or pharmacist before combining Quercetin with any medicine.

Quercetin drug interactions

Known or theoretical interactions between Quercetin and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Quercetin with any medicine.

Caution
Antiplatelet drugs (aspirin, clopidogrel)
High-dose quercetin can inhibit platelets and enhance aspirin's antiplatelet effect, raising bleeding risk.
Quercetin and its metabolites inhibit platelet aggregation and act more-than-additively with aspirin. Quercetin metabolites + aspirin antiplatelet effects (PMC)
Caution
Blood thinners (warfarin, DOACs)
High-dose quercetin may interfere with warfarin and add antiplatelet effects; monitor INR and bleeding.
Quercetin metabolites displace warfarin from serum albumin and inhibit platelet aggregation. Quercetin–warfarin interaction (PubMed)
Monitor
CYP3A4 drugs (e.g. cyclosporine, statins, CCBs)
May alter blood levels of CYP3A4/P-gp drugs such as cyclosporine; monitor levels and effects.
Quercetin can inhibit CYP3A4 and modulate P-glycoprotein, changing the metabolism and transport of these drugs. NIH PMC — Cyclosporine & Herbal Supplement Interactions · PubMed — Effect of quercetin on oral cyclosporine pharmacokinetics

Key Studies

Systematic review Huang 2023 (umbrella review) ✓ Full text
Umbrella review of 5 meta-analyses: significant systolic-BP drop (WMD −1.9 mmHg) and lower insulin; no effect on diastolic BP, lipids, inflammation, FPG or HOMA-IR.
Meta-analysis Ou 2020 ✓ PubMed
Meta-analysis: no overall effect on CRP, IL-6 or TNF-α; CRP and IL-6 fell only in subgroups with diagnosed disease or high doses.
Meta-analysis Serban 2016 ✓ PubMed
Meta-analysis (7 trials, 9 arms, 587 patients): quercetin cut systolic BP by 3.04 mmHg (95% CI −5.75 to −0.33), effect greater at >500 mg/day.
Meta-analysis Mohammadi-Sartang 2017 ✓ PubMed
Meta-analysis (7 RCTs): quercetin lowered CRP by 0.33 mg/L (95% CI −0.50 to −0.15); effect strongest at ≥500 mg/day.
Meta-analysis Ostadmohammadi 2019 ✓ Full text
Meta-analysis in metabolic syndrome: no overall effect on FPG, HOMA-IR or HbA1c; FPG fell only with ≥500 mg/day for ≥8 weeks.
Meta-analysis Sahebkar 2017 ✓ PubMed
Meta-analysis (5 RCTs, 442 subjects): no significant effect on LDL, HDL or triglycerides; a small non-relevant rise in total cholesterol.
RCT Shi 2016 ✓ PubMed
Crossover RCT (22 pre-hyperuricaemic men): 500 mg/day for 4 weeks lowered plasma uric acid by 26.5 µmol/L (P=0.008), no change in BP or glucose.
RCT Heinz 2010 ✓ PubMed
RCT (N=1002, 500 & 1000 mg/day, 12 wk): no reduction in upper-respiratory-infection rate, severity or duration vs placebo overall.
8 sources cited · 8 verified Search all studies on PubMed ↗

Common questions about Quercetin

What is Quercetin used for?

Quercetin is most often taken for Modestly lower blood pressure, Lower CRP in inflamed/diseased groups, Lower uric acid, Antioxidant flavonoid support. Plant flavonoid with a modest, dose-dependent blood-pressure effect.

Does Quercetin work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Quercetin is a flavonoid found in onions, apples, tea and capers, sold as an antioxidant, anti-inflammatory and immune supplement. The most reproducible human finding is blood pressure: pooled RCTs report a systolic reduction of about 1.9–3.0 mmHg, seen mainly at doses ≥500 mg/day. A small crossover trial found 500 mg/day lowered plasma uric acid by ~26 µmol/L in pre-hyperuricaemic men. Effects on C-reactive protein are inconsistent—null overall but significant in people with established disease or at high doses. Meta-analyses generally find no effect on lipids, and only subgroup (≥500 mg, ≥8 weeks) effects on fasting glucose. The popular cold/immune claim is weak: a 1,002-person community trial found no reduction in respiratory infections, with benefit limited to smaller exercise-stressed groups. Most trials are short (4–12 weeks) and bioavailability is poor, so real-world benefits are likely small.

What is the typical dose of Quercetin?

500–1000 mg/day of quercetin (often as aglycone or phytosome/isoquercetin for absorption); the BP and uric-acid signals appear at ≥500 mg/day.

Is Quercetin safe? Any cautions or side effects?

Oral quercetin is generally well tolerated up to ~1000 mg/day for several weeks; reported effects are mild (headache, tingling, GI upset), and high-dose or IV use has been linked to kidney toxicity. As a CYP3A4/CYP2C9 and P-glycoprotein inhibitor it can raise levels of drugs with narrow therapeutic windows—warfarin and other anticoagulants, cyclosporine and some statins—and may add to the glucose- and BP-lowering effects of antidiabetic and antihypertensive medication. Long-term safety data are lacking; avoid high doses in pregnancy, breastfeeding, and kidney disease, and separate from medications if you take CYP3A4 substrates.

How many studies support Quercetin?

NutriDex cites 8 sources for Quercetin, graded "Moderate".

Does Quercetin interact with any medications?

Yes — known or theoretical interactions include: Antiplatelet drugs (aspirin, clopidogrel) (caution), Blood thinners (warfarin, DOACs) (caution), CYP3A4 drugs (some statins, CCBs, immunosuppressants) (monitor). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Quercetin with any medicine.

Cite this page
APA

Peh, D. (2026). Quercetin: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/quercetin

BibTeX
@misc{nutridex_quercetin,
  author       = {Peh, Daryl},
  title        = {Quercetin: Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/quercetin},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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