What quercetin does in your body and how much to take
Updated · 8 studies cited · 5 products compared
Short answer
Quercetin is a plant compound found in foods like onions and apples. Its best-tested effect is a small drop in blood pressure. The drop is too small to replace your medicine. For colds, the studies disagree.
- What it helps
- A small drop in blood pressure. That is its best-tested effect.
- How much
- More than 500 mg a day in blood pressure studies. 1,000 mg a day in exercise studies.
- How long
- Studies give no clear answer. Plan on at least 8 weeks.
- How sure are we
- Some proof
- Skip it or ask first
- Ask your doctor first if you have kidney disease, a cancer that grows on the hormone estrogen, or take prescription medicine.
See details
The best-documented effect of quercetin in people is a small drop in blood pressure, about 3 mmHg, and it may only appear above 500 mg a day.12 Its effect on infections is uncertain, since two similar trials in endurance athletes disagreed.56
More than 500 mg a day in blood pressure trials;2 1,000 mg a day in exercise trials5
Ask first if you have kidney disease or an estrogen-dependent cancer, or take prescription medication.8
How does quercetin work in your body?
Lab and animal studies point to two things. Quercetin seems to calm a body chemical that tightens your blood vessels. It also seems to help the lining of those vessels work well. Both could let blood flow with less pressure. This has not been proven in people yet.
See details
Lab and animal studies suggest quercetin acts on angiotensin-converting enzyme and on the lining of blood vessels, both of which help set blood pressure.4 These pathways offer a plausible explanation for the trial results, but they have not been confirmed as the cause in people.
What does quercetin do, and how much does it help?
You get some quercetin from onions and apples. Supplements give far more than most food does.
Blood pressure
Helps a littleIt dropped by a small amount, mostly when people took more than 500 mg a day. You would likely not notice it, and it does not replace treatment.
How long: Studies give no clear time. Plan on at least 8 weeks.
See details
Some proof
Pooling 17 trials and 896 people, one analysis found systolic pressure fell by 3.09 mmHg and diastolic by 2.86 mmHg.1 Another, with 7 trials and 587 people, reached similar numbers and suggested that the effect may be limited to doses above 500 mg a day.2 A third found that diastolic pressure fell by 3.14 mmHg in people with high or borderline-high pressure.3 A change of this size is small for one person, and it doesn't replace treatment.
Trial length varied. Lipid changes appeared at 8 weeks or longer, so we would allow at least that long.
Colds after hard exercise
Not sure yetIn one study, cyclists who took it got far fewer colds after hard riding. In another, runners got no help. Neither tells us much about people who aren't athletes.
How long: Both studies started about 3 weeks before the exercise.
See details
Little proof
Forty trained cyclists took 1,000 mg a day or placebo around three days of hard riding. Over the next two weeks, 1 of 20 on quercetin got an upper respiratory infection, against 9 of 20 on placebo, although immune markers didn't differ.5 Ultramarathon runners on the same dose had no fewer illnesses than the placebo group.6 Neither study tells us much about non-athletes.
Both trials started about 3 weeks before the exercise.
Cholesterol and blood fats
No clear helpChanges showed up only in some small groups. We wouldn't buy it for this.
See details
Little proof
HDL cholesterol and triglycerides changed only in subgroups, in parallel-design trials lasting at least 8 weeks.1 We wouldn't buy quercetin for this.
Kidneys and other safety worries
Possible riskLab and animal studies raised two worries. It may make a hurt kidney worse, and it may feed cancers that grow on estrogen. It can also change the level of some drugs in your blood. These harms aren't proven, but they matter if any of this applies to you.
See details
Little proof
A safety review raised two concerns from lab and animal work: quercetin may worsen damage in an already injured kidney, and it might promote estrogen-dependent tumors. Human studies also show interactions that change drug levels.8 These are signals rather than established harms, but they matter if you fall into one of those groups.
How well does your body absorb quercetin?
Some forms soak in better than others. Special forms called phytosome are made to soak in better, so you can't compare them by the number on the label.
See details
Absorption differs among polyphenols. In a review of 97 bioavailability studies, quercetin glucosides, the form found in onions, were absorbed reasonably well compared with other flavonoids, but with their own kinetics.7 Phytosome products try to improve absorption by binding quercetin to phospholipids. The milligram figure on those labels can't be compared directly with plain quercetin.
Do you need bromelain with quercetin?
We see no good reason to pay more for it. Many products add it, saying it helps quercetin soak in. The studies here did not test that.
See details
Many products add bromelain on the theory that it improves absorption. The trials cited here don't test that combination, so they give no reason to pay more for it.
Best quercetin supplements by study dose and cost a day
Plain 500 mg quercetin comes first because it is easiest to compare with the studies.
Cost a day is for about 1,000 mg a day, the amount from the exercise studies.
| Product | Cost a day | Lasts |
|---|---|---|
| California Gold Nutrition, Quercetin, 500 mg, 180 Veggie Capsules2 capsules a day (label says 1) | $0.40Lowest | 90 days |
| NOW Foods, Quercetin, 500 mg, 100 Veg Capsules2 capsules a day | $0.42 | 50 days |
| NOW Foods, Quercetin with Bromelain, 120 Veg Capsules3 capsules a day, which gives 1,200 mg (label says 2) | $0.58 | 40 days |
| Natural Factors, Quercetin, 500 mg, 60 Vegetarian Capsules2 capsules a day (label says 1) | $0.67 | 30 days |
| California Gold Nutrition, Quercetin Phytosome, Quercefit, 250 mg, 60 Veggie Capsules1 capsule a day, as the label says · Different form, hard to compare | $0.33 | 60 days |
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1
Natural Factors, Quercetin, 500 mg, 60 Vegetarian Capsules
1 capsule: 500 mg quercetin
Plain quercetin with lots of reviews. Two capsules give the 1,000 mg from the exercise studies.
View on iHerb$0.67 a day
2 capsules a day (label says 1)
$20.16 on iHerb for 30 days -
2
California Gold Nutrition, Quercetin, 500 mg, 180 Veggie Capsules
1 capsule: 500 mg quercetin
Plain quercetin, and the label clearly says how much.
View on iHerb$0.40 a day Lowest cost here
2 capsules a day (label says 1)
$36.10 on iHerb for 90 days -
3
NOW Foods, Quercetin, 500 mg, 100 Veg Capsules
2 capsules: 1,000 mg quercetin
Two capsules give the 1,000 mg from the exercise studies.
View on iHerb$0.42 a day
2 capsules a day
$21.20 on iHerb for 50 days -
4
NOW Foods, Quercetin with Bromelain, 120 Veg Capsules
2 capsules: 800 mg quercetin + 165 mg bromelain
Close on quercetin, but the added bromelain was not in these studies.
View on iHerb$0.58 a day
3 capsules a day, which gives 1,200 mg (label says 2)
$23.34 on iHerb for 40 days -
5
California Gold Nutrition, Quercetin Phytosome, Quercefit, 250 mg, 60 Veggie Capsules
1 capsule: 250 mg quercetin phytosome
A special form. You can't compare it by the number on the label.
View on iHerb$0.33 a day
1 capsule a day, as the label says
$19.78 on iHerb for 60 days
Amounts and US prices come from each product's iHerb page on November 6, 2026. Prices change often and differ by country, so check the current price on iHerb. Shipping and tax are not included. How we rank products
Common questions
How much quercetin should I take?
Blood pressure studies worked better above 500 mg a day. Exercise studies used 1,000 mg. Ask your doctor if you take other medicine.
How long does quercetin take to lower blood pressure?
Studies give no clear answer. Plan on at least 8 weeks.
See details
Reviews don't give a clear time course. Some lipid changes appeared only at 8 weeks or more,1 which gives a rough idea of how long you'd need to take it.
Is quercetin safe?
Short studies raised few alarms. But a safety review flagged kidney harm, some cancers, and problems with other drugs.
See details
Short-term trials have not raised many alarms, but a safety review flagged kidney damage, estrogen-dependent cancers, and drug interactions.8
Does quercetin help with allergies?
We didn't find strong studies in people, so we haven't rated it.
See details
We didn't find strong human trials on this while preparing this page, so we haven't graded it.
Who should not take quercetin?
- Kidney disease: it may make a hurt kidney worse.
- A cancer that grows on estrogen: a possible risk has been raised, mostly from lab work.
- Prescription drugs: it can change how your body takes in some drugs.
- Pregnant or breastfeeding: we don't know if these amounts are safe.
Studies we used
See all 8 studies
- Meta-analysis or review
17 trials, 896 people. Blood pressure fell by 3.09/2.86 mmHg; lipid changes only in some subgroups.
Effect of quercetin supplementation on plasma lipid profiles, blood pressure, and glucose levels: a systematic review and meta-analysis. Nutr Rev, 2020. PubMed 31940027
- Meta-analysis or review
7 trials, 587 people. Blood pressure fell, possibly limited to doses above 500 mg a day.
Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Am Heart Assoc, 2016. PubMed 27405810
- Meta-analysis or review
10 trials, 841 people. Systolic pressure fell by 2.38 mmHg overall.
The Effects of Quercetin Supplementation on Blood Pressure - Meta-Analysis. Curr Probl Cardiol, 2022. PubMed 35948195
- Guideline or expert review
Review of quercetin's cardiovascular mechanisms, including ACE activity and endothelial function.
Therapeutic potential of quercetin as a cardiovascular agent. Eur J Med Chem, 2018. PubMed 29966915
- Clinical trial
40 cyclists, 1,000 mg a day. Infection in 1 of 20 versus 9 of 20 on placebo.
Quercetin reduces illness but not immune perturbations after intensive exercise. Med Sci Sports Exerc, 2007. PubMed 17805089
- Clinical trial
63 ultramarathon runners, 1,000 mg a day. No effect on illness rates.
Post-160-km race illness rates and decreases in granulocyte respiratory burst and salivary IgA output are not countered by quercetin ingestion. Int J Sports Med, 2008. PubMed 18213545
- Meta-analysis or review
97 bioavailability studies. Compares absorption across polyphenols.
Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. Am J Clin Nutr, 2005. PubMed 15640486
- Guideline or expert review
Safety review. Flags kidney damage, estrogen-dependent cancer, and drug interactions.
Safety Aspects of the Use of Quercetin as a Dietary Supplement. Mol Nutr Food Res, 2018. PubMed 29127724