Quercetin: dosage, bioavailability, and why the form matters more than the milligrams
· by VEXTA Team
The real limiting factor
Quercetin is a flavonoid abundant in food — capers, red onion, apple, tea. The problem with supplementation has never been supplying enough: it is getting it absorbed.
Quercetin aglycone, the most common and cheapest form, is poorly absorbed orally. That is precisely why formulation research is so active — phytosomes, complexation, lipid pairings — and why human trials use those rather than the raw form.
The direct consequence: 1,000 mg of a poorly absorbed form can deliver less than 200 mg of a form engineered for absorption. The figure on the label measures what went into the capsule, not what gets into you.
What human trials actually use
The most developed human trial on quercetin in an allergic context (Yamada 2022, PMID 35776034) used 200 mg of Quercetin Phytosome® daily for four weeks in 66 people. The authors explicitly state they used a food-grade bioavailable formulation.
That is first-order information when choosing a product: the 200 mg figure only means something attached to that form. Applying the number to standard quercetin is copying a protocol while deleting half of it.
The rest of the anti-allergic literature — thirteen studies synthesised by Lv 2025 (DOI 10.3389/fphar.2025.1673712) — is in animal models, where absorption questions arise differently.
How to read a label
In order:
- Form first. Standard aglycone, phytosome, lipid complex, piperine pairing? That is the first line to look for, before the dose.
- Dose second, interpreted in light of the form.
- Source. Most market quercetin comes from Sophora japonica extract.
- Purity, where published.
A product leading with a large number but not stating its form is avoiding the only question that matters.
Timing and duration
Flavonoids are better absorbed with a meal, particularly one containing fat. No trial compares morning with evening dosing.
The evaluation window consistent with the published trial is four weeks. For a seasonal allergy, that means evaluating during exposure — an off-season test tells you nothing.
Finally, the caveat that applies to every supplement: if you are on medication, the question is one of interactions, and it belongs with a doctor or pharmacist.