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Quercetin

Quercetin

Best for

Catch fewer colds and infections

Likely strong benefit · 250 mg/day for 12 weeks · 1 study , n=120

40 papers · 8 claims · 108 outcomes scored · 5 positive

Evidence summary

Evidence summary

Likely strong benefit

Quercetin shows a likely strong benefit for fewer colds and infections in athletes, alongside a modest blood-pressure drop in hypertensive adults.

  • Across 1 study (n=120), quercetin reduced upper respiratory tract illness in athletes.3
  • Quercetin also lowered blood pressure in hypertensive adults, giving a second human benefit signal.2
  • Most positive findings come from athletes and hypertensive adults, not general healthy users.

Outcomes

What quercetin actually does, by outcome

Each row is one outcome with effect size, evidence base, the dose that worked in trials, and time to first effect. Magnitude tiers come from native-unit MCID where available, Cohen's d otherwise.

Catch fewer colds and infections Likely strong benefit

Your immune barriers intercept more viruses before they take hold.

1 RCT n=120 250 mg 12 wk #3/17
35054459
Improve insulin sensitivity Large effect, needs confirmation

Your cells respond to insulin again so your pancreas works less hard.

2 RCTs n=106 1000 mg 1–12 wk
29105398·35571883
Steady your blood sugar levels Large effect, needs confirmation

Keeps fasting glucose and your three-month average in a healthier range.

2 RCTs n=82 400–1000 mg 10–12 wk
21487493·29105398
Flatten post-meal blood sugar spikes Promising early signal

Blunts the glucose surge after eating so energy stays level.

1 RCT n=24 1000 mg 1 wk
35571883
Lower your blood pressure Proven modest benefit

Brings down both systolic and diastolic, especially when baseline runs high.

6 meta-analyses n=759 100–1000 mg 6–10 wk #2/79
19402938·21487493·24049596·24829713 +2 more
Lower bad and total cholesterol Not enough research

Cuts the cholesterol that builds into artery plaque over time.

2 RCTs n=— 150–400 mg 6–10 wk
19402938·21487493
Lower triglycerides Not enough research

Reduces the blood fats that rise after meals and drive heart risk.

1 RCT n=— 400 mg 10 wk
21487493
Raise good cholesterol levels May have slight negative effect

Boosts the cholesterol that pulls fat out of artery walls.

2 RCTs n=278 150–400 mg 6–10 wk
19402938·21487493

Forms & standardisation

Most of the human data uses plain quercetin capsules or tablets, so that is the form with the cleanest trial match.13 On a label, look for the actual quercetin amount in milligrams, not just a vague "bioflavonoid" blend. Fancy delivery systems exist, but the best evidence still tracks with the simple ingredient.

Risk profile

Adverse events and known drug interactions

Safety events

treatment-related_carcinogenic_lesions (kidney, urinary bladder, intestine) in male rats severe
anaphylaxis severe
pneumonia severe
gastroenteritis severe
urinary_tract_infection severe
pro-oxidant effects in glutathione-depleted states; metabolic interactions affecting estrogen metabolism moderate
No serious adverse events reported in included RCTs; minor side-effects (headache, nausea, tingling) noted in other long-term reports mild
gastro-oesophageal reflux disease mild

Drug interactions

Tacrolimus major increases concentration
Carbamazepine major increases concentration
Antidepressants major increases concentration
Antipsychotics major increases concentration
Selexipag major increases concentration
Diclofenac major increases concentration
Warfarin major increases concentration
Quetiapine major increases concentration
Tucatinib major increases concentration
Cyclosporine moderate increases concentration

Co-studied with

Supplements that share evidence with quercetin

Vitaminc 14 shared outcomes · d=0.99
Niacin 14 shared outcomes · d=0.99
Greentea 2 shared outcomes · d=2.80

Frequently asked

Common questions

Does quercetin lower blood pressure?

Yes, the human data shows a small drop, mostly after 6–10 weeks of daily use, and the effect shows up more when your baseline pressure already runs high.12

How much quercetin do people study?

For blood pressure, the useful trials cluster around 500 mg/day, while the cold-season study used 250 mg/day for 12 weeks.13

Is quercetin worth it for colds?

If colds are your main target, quercetin has one encouraging human study, but the evidence is still much thinner than it is for blood pressure.3

When should you take quercetin?

Take it every day and keep the schedule steady for weeks. Quercetin acts like a long-game supplement, not a same-day fix.13

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Sources

  1. 1. Quercetin reduces blood pressure in hypertensive subjects
  2. 2. Effect of quercetin on blood pressure: a systematic review and meta-analysis of randomized controlled trials
  3. 3. Quercetin supplementation and upper respiratory tract illness in athletes

Generated May 15, 2026

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