Heart/Weight/Inflammation

Quercetin

Plant flavonoid from onions and apples that may modestly support blood pressure, glucose, and inflammation markers in adults.

Quercetin

Plant flavonoid from onions and apples that may modestly support blood pressure, glucose, and inflammation markers in adults.

score

evidence

Caution

risk

Proven Benefits

01Lowers systolic blood pressure

02Improves fasting glucose

03Lowers hs-CRP modestly

04May lower LDL cholesterol

05May improve endothelial function

Chemical Forms

Recommended

Quercetin phytosome
Isoquercetin
Enzymatically modified isoquercitrin (EMIQ)

Avoid

Plain quercetin aglycone powder (poor solubility, variable absorption)

Expert Note

Isoquercetin and EMIQ generally dissolve better and produce higher, more consistent plasma levels than plain quercetin aglycone. Phytosome forms can also improve absorption by pairing quercetin with phospholipids. Basic bulk quercetin powder is often the cheapest but the least predictable.

Protocol

Amount

500-1000 mg

Frequency

Once daily or split into 2 doses

When

With meals; consistency matters more than timing, and enhanced-absorption forms may work at lower doses.

Condition-Based Dosing

Standard quercetin products

500-1000 mg daily for 8-12 weeks— Most human cardiometabolic studies use this range.

Enhanced-absorption forms such as phytosome or isoquercetin

Use the labeled clinically studied dose, often lower than plain quercetin— Do not assume milligram-for-milligram equivalence with basic quercetin powder.

Safety & Limits

Upper Safe Limit

1000 mg/day (common studied adult dose; no official UL established)

Cycling

Safe for continuous use

Contraindications

Pregnancy or breastfeeding — insufficient supplemental safety data

Kidney disease — avoid high-dose use without clinician oversight

Iron deficiency or low ferritin — can reduce non-heme iron absorption

Cyclosporine, digoxin, tacrolimus, or other narrow-therapeutic-index drugs — quercetin may alter drug transport or metabolism

Synergies

Vitamin C

Vitamin C may help recycle oxidized quercetin and is commonly paired with it, though evidence that the combo clearly outperforms quercetin alone is limited.

Avoid Combining With

✕Iron supplements or iron-rich meals (separate by 2+ hours — quercetin can reduce non-heme iron absorption)

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