Isoquercetin

PhytochemicalFlavonoidBest with a meal

What is it

Isoquercetin (quercetin-3-O-glucoside) is a flavonoid glycoside found in onions, apples, and other plants. It is the glucoside form of quercetin and is generally more bioavailable than free quercetin aglycone.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Quercetin bioavailability enhancement

Good Evidence

Pharmacokinetic studies consistently show higher and faster plasma quercetin levels from isoquercetin compared to equal doses of quercetin aglycone.

Prevention of cancer-associated thrombosis (research stage)

Limited Evidence

A high-dose isoquercetin trial in cancer patients showed reduced markers of clotting risk. Larger trials are ongoing.

How it works

Isoquercetin is rapidly absorbed in the small intestine via the SGLT1 glucose transporter, then hydrolyzed to quercetin in the body. This makes peak plasma quercetin levels higher and faster than with quercetin aglycone supplementation. Quercetin metabolites have antioxidant and anti-inflammatory effects in laboratory studies. Clinical research has explored uses in cardiovascular health, allergies, exercise recovery, and prevention of cancer-associated thrombosis.

Dosage

Common doses in clinical trials range from 250-500 mg twice daily. Enzymatically modified isoquercitrin (EMIQ) is also bioavailable and used in similar doses.

When and how to take it

Often taken twice daily with meals to maintain steady plasma quercetin levels. Around exercise for recovery-related uses.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Isoquercetin (quercetin-3-glucoside)

Used in cardiovascular and antioxidant supplements.

Higher bioavailability than quercetin aglycone

EMIQ (enzymatically modified isoquercitrin)

Used in some allergy and bioavailability products.

Modified to further enhance solubility

Safety

Generally well-tolerated. High-dose intravenous use has been studied in oncology trials with acceptable safety. Oral doses up to 1000 mg/day have been used in trials with minimal adverse effects.

Who should be cautious

Limited safety data in pregnancy and breastfeeding for concentrated extracts. People on multiple prescription medications should review interactions.

Interactions

May modestly inhibit several CYP enzymes. Quercetin and its glycosides may increase plasma levels of some medications metabolized by CYP3A4. Discuss with your clinician if you take prescription drugs.

Food sources

Onions, apples, capers

Amount
varies
%DV
—

Frequently asked questions

Is isoquercetin better than quercetin?⌄

It is more bioavailable per milligram, so lower doses can produce similar plasma levels.

Does it have side effects?⌄

Generally well-tolerated. Like all polyphenol supplements, possible mild GI upset.

References

Isoquercetin on Wikidata — Wikidata link

Isoquercetin (ChEBI:68352) — ChEBI link

Isoquercetin (PubChem CID 5280804) — PubChem link

Isoquercetin on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Isoquercetin (PubMed search) — PubMed link

Track Isoquercetin with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.