Drug & supplement interaction

Quercetin + Verapamil

Verapamil brand names: Isoptin SR, Verelan, Isoptin, Calan SR, Verelan SR, and others.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Verapamil falls into 4 drug categories that Quercetin can interact with; the most serious is rated moderate. Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions4
EvidenceB
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Quercetin and Verapamil

These two interact in 4 distinct ways. Each one is explained separately below.

Why Are There 4 Interactions?

Quercetin interacts with whole categories of medication. Verapamil falls into 4 of those categories, so it can interact with Quercetin in 4 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 4

Why this applies to Verapamil

Verapamil falls under ANTIHYPERTENSIVE DRUGS — the group Quercetin interacts with.

Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Quercetin can modestly decrease blood pressure in people with mild hypertension. Theoretically, it might have additive blood pressure lowering effects when used with antihypertensive drugs.
Severity Moderate Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: verapamil already lowers your blood pressure by relaxing blood vessels and easing the workload on your heart. Quercetin, in concentrated supplement doses, has been shown in some smaller studies to nudge blood pressure down a bit on its own. Stack the two together and those effects can add up, so your pressure could dip lower than intended.

If that happens, you might feel dizzy, lightheaded, unusually tired, or a bit faint, especially when standing up quickly. This is mostly a concern with high-dose supplements, not the small amounts of quercetin you'd get from foods like apples or onions. The evidence here is fairly modest, so don't panic. Just check with your pharmacist or doctor before starting a quercetin supplement, and they may want to keep an eye on your blood pressure.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-11.
  2. Larson A, Witman MA, Guo Y, et al. Acute, quercetin-induced reductions in blood pressure in hypertensive individuals are not secondary to lower plasma angiotensin-converting enzyme activity or endothelin-1: nitric oxide. Nutr Res. 2012;32(8):557-64. PubMed
Moderate

P-GLYCOPROTEIN SUBSTRATES

2 of 4

Verapamil also falls under P-GLYCOPROTEIN SUBSTRATES.

Theoretically, concomitant use might alter the effects and adverse effects of P-glycoprotein substrates.

There is preliminary evidence that quercetin inhibits the gastrointestinal P-glycoprotein efflux pump, which might increase the bioavailability and serum levels of drugs transported by the pump. A small study in healthy volunteers reported that pretreatment with quercetin increased bioavailability and plasma levels after a single dose of cyclosporine (Neoral, Sandimmune). Also, two small studies have shown that quercetin might decrease the absorption of talinolol, a substrate transported by the gastrointestinal P-glycoprotein efflux pump. However, in another small study, several days of quercetin treatment did not significantly affect the pharmacokinetics of saquinavir (Invirase). The reason for these discrepancies is not entirely clear. Until more is known, use quercetin cautiously in combination with P-glycoprotein substrates.
Severity Moderate Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: verapamil is carried around your body partly by a little cellular pump called P-glycoprotein. Quercetin, in higher supplement doses, may block that pump. If that happens, more verapamil could get absorbed and linger in your bloodstream. Verapamil is already active as-is (it's not a prodrug), so higher levels mean a stronger effect.

In plain terms, you might see more of verapamil's usual effects: lower blood pressure, dizziness, a slower or more sluggish heartbeat, tiredness, or constipation. To be fair, the evidence here is mostly theoretical and based on small studies, so it's a could happen, not a will happen. Food amounts of quercetin almost certainly don't matter. Before starting a concentrated supplement, just run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. DiCenzo R, Frerichs V, Larppanichpoonphol P, et al. Effect of quercetin on the plasma and intracellular concentrations of saquinavir in healthy adults. Pharmacotherapy 2006;26:1255-61. PubMed
  2. Choi JS, Choi BC, Choi KE. Effect of quercetin on the pharmacokinetics of oral cyclosporine. Am J Health Syst Pharm 2004;61:2406-9. PubMed
  3. Choi JS, Jo BW, Kim YC. Enhanced paclitaxel bioavailability after oral administration of paclitaxel or prodrug to rats pretreated with quercetin. Eur J Pharm Biopharm 2004;57:313-8. PubMed
  4. Wang SY, Duan KM, Li Y, et al. Effect of quercetin on P-glycoprotein transport ability in Chinese healthy subjects. Eur J Clin Nutr 2013;67(4):390-4. PubMed
  5. Nguyen MA, Staubach P, Wolffram S, Langguth P. Effect of single-dose and short-term administration of quercetin on the pharmacokinetics of talinolol in humans - Implications for the evaluation of transporter-mediated flavonoid-drug interactions. Eur J Pha PubMed
  6. Zhao Q, Wei J, Zhang H. Effects of quercetin on the pharmacokinetics of losartan and its metabolite EXP3174 in rats. Xenobiotica 2019;49(5):563-8. PubMed
  7. Bhutani P, Rajanna PK, Paul AT. Impact of quercetin on pharmacokinetics of quetiapine: insights from in-vivo studies in wistar rats. Xenobiotica. 2020:1-7.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

3 of 4

Verapamil also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, concomitant use might alter the effects and adverse effects of CYP3A4 substrates.
A small clinical study in healthy volunteers shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of a single dose of cyclosporine (Neoral, Sandimmune), a substrate of CYP3A4. Animal research also shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar) and quetiapine (Seroquel), substrates of CYP3A4. Other laboratory research also shows that quercetin inhibits CYP3A4. However, one clinical study shows that quercetin can increase the metabolism of midazolam, a substrate of CYP3A4, and decrease serum concentrations of midazolam by about 24% in some healthy individuals, suggesting possible induction of CYP3A4.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: your body relies on a liver enzyme called CYP3A4 to break down verapamil. Quercetin may interfere with that enzyme, and the lab and animal data point in two different directions. In most studies quercetin slows this enzyme, which could let more verapamil build up. If that happens, you might notice things like dizziness, unusually low blood pressure, a slower heart rate, fatigue, or constipation. A bit of research even hints quercetin could speed the enzyme up in some people, which would do the opposite and weaken the drug.

The honest truth is this is mostly theoretical and based on weak evidence. Food amounts of quercetin are unlikely to cause trouble, but high-dose supplements are worth running by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Obach RS. Inhibition of human cytochrome P450 enzymes by constituents of St. John's wort, an herbal preparation used in the treatment of depression. J Pharmacol Exp Ther 2000;294:88-95. DOI
  2. DiCenzo R, Frerichs V, Larppanichpoonphol P, et al. Effect of quercetin on the plasma and intracellular concentrations of saquinavir in healthy adults. Pharmacotherapy 2006;26:1255-61. PubMed
  3. Choi JS, Choi BC, Choi KE. Effect of quercetin on the pharmacokinetics of oral cyclosporine. Am J Health Syst Pharm 2004;61:2406-9. PubMed
  4. Choi JS, Jo BW, Kim YC. Enhanced paclitaxel bioavailability after oral administration of paclitaxel or prodrug to rats pretreated with quercetin. Eur J Pharm Biopharm 2004;57:313-8. PubMed
  5. Duan KM, Wang SY, Ouyang W, Mao YM, Yang LJ. Effect of quercetin on CYP3A activity in Chinese healthy participants. J Clin Pharmacol 2012;52(6):940-6. PubMed
  6. Zhao Q, Wei J, Zhang H. Effects of quercetin on the pharmacokinetics of losartan and its metabolite EXP3174 in rats. Xenobiotica 2019;49(5):563-8. PubMed
  7. Bhutani P, Rajanna PK, Paul AT. Impact of quercetin on pharmacokinetics of quetiapine: insights from in-vivo studies in wistar rats. Xenobiotica. 2020:1-7.
Moderate

CYTOCHROME P450 2C8 (CYP2C8) SUBSTRATES

4 of 4

Verapamil also falls under CYTOCHROME P450 2C8 (CYP2C8) SUBSTRATES.

Theoretically, concomitant use might increase the levels and adverse effects of CYP2C8 substrates.

In vitro research shows that quercetin inhibits CYP2C8. Inhibition of paclitaxel (Taxol) metabolism via CYP2C8 has been reported in vitro. However, a small study in humans found no effect of quercetin on rosiglitazone (Avandia), which is also a CYP2C8 substrate.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: in a test tube, quercetin can slow down a liver enzyme called CYP2C8, which is one of the pathways that helps clear verapamil from your body. Verapamil is an active drug, not a prodrug, so if that pathway slows, the theory is that more verapamil could hang around than usual. With a heart medication like this, that could mean a bit too much of its normal effects, things like lightheadedness, low blood pressure, a slower heartbeat, swollen ankles, or constipation.

That said, this is theoretical and based only on lab work. In a real human study, quercetin didn't change a similar drug. Food amounts of quercetin are very unlikely to matter, but before starting a high-dose supplement, run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Kim KA, Park PW, Kim HK, et al. Effect of quercetin on the pharmacokinetics of rosiglitazone, a CYP2C8 substrate, in healthy subjects. J Clin Pharmacol 2005;45:941-6. PubMed
  2. Choi JS, Jo BW, Kim YC. Enhanced paclitaxel bioavailability after oral administration of paclitaxel or prodrug to rats pretreated with quercetin. Eur J Pharm Biopharm 2004;57:313-8. PubMed
  3. Vaclavikova R, Horsky S, Simek P, Gut I. Paclitaxel metabolism in rat and human liver microsomes is inhibited by phenolic antioxidants. Naunyn Schmiedebergs Arch Pharmacol 2003;368:200-9. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Quercetin Also Interacts With Other Medications

Quercetin has 1,168 moderate known drug interactions in our database — the Verapamil one above is among them. If you take anything else, check it against the full list below.

Moderate 1,168 No known interaction 1,662 (incl. Verapamil)
Taking anything else?

Check Another of Your Medications Against Quercetin

Covers the 2,830 medications we’ve checked against Quercetin. Pick one to open its full report.

From our Q&A

Questions About Quercetin or Verapamil

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Quercetin or Verapamil, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Verapamil

This page covers Quercetin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Verapamil page lists 295 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Beer (major) and Coleus (major).

By severity: 10 major · 245 moderate · 40 minor.

From our pharmacist’s overview on the Verapamil page

“This is one of the longer interaction lists we publish, and with verapamil (Calan, Verelan) it warrants genuine care, starting with the ten major-rated entries. Verapamil lowers blood pressure and slows the heart, so most of the 295 ingredients on file either push that effect further than intended or change how much of the drug reaches…”

Reviewed by 2 · Jul 18, 2026

Open the Verapamil interaction page

One more smart check

Taking Quercetin as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,589 real supplement products containing Quercetin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Quercetin. Your product may carry other ingredients that interact with Verapamil too, on top of Quercetin — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Quercetin and Verapamil Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Quercetin
Top 5%

#48 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Verapamil
Top half

#731 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Quercetin

What is Quercetin?

Quercetin
  • Seasonal allergies
  • Antioxidant support
  • Heart and blood pressure health
  • Anti-inflammatory support
  • Immune support
  • Exercise recovery

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early research is interesting for allergies, blood pressure, and inflammation, strong human evidence is limited for most uses. It is generally well tolerated in food amounts, but talk to your pharmacist or doctor before taking high-dose supplements.

Read the full Quercetin monograph & all interactions
Medication

About Verapamil

What Is Verapamil Used For?

Brand names: Isoptin SR, Verelan, Isoptin, Calan SR, Verelan SR, Calan, Covera HS, Verap, Veramil

Verapamil tablets and film-coated tablets are used to treat angina — including vasospastic (Prinzmetal's) angina, unstable angina, and chronic stable angina — as well as certain abnormal heart rhythms (arrhythmias) and high blood pressure (essential hypertension). For arrhythmias, regular-release tablets are used alongside digoxin to control heart rate in atrial flutter or atrial fibrillation, and to help prevent episodes of paroxysmal supraventricular tachycardia (SVT), a type of rapid heartbeat.

Extended-release and sustained-release oral forms (tablets and capsules) are indicated specifically for high blood pressure. Verapamil hydrochloride injection is used in hospital settings for rapid conversion of SVT to normal rhythm and for temporary control of fast heart rates in atrial flutter or atrial fibrillation.

See full Verapamil drug information
Keep checking

Other Drugs & Quercetin

Browse every other medication we’ve checked against Quercetin — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
1,168Moderate
0Minor
1,661No known interaction
1,168 Moderate 1,661 No interaction
Moderate

1,168 interactions

Showing 60 of 1,168 moderate interactions — see all 1,168 on the Quercetin page.

No interaction 1,661 drugs checked — show the list

We also checked Quercetin against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,661 medications checked with no known interaction — see the full Quercetin list.

See the full Quercetin interactions page
See every supplement checked against Verapamil, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Quercetin monograph › Uses, safety, and every drug interaction in one place Verapamil supplement interactions › Every supplement checked against Verapamil, ranked by severity Verapamil drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Quercetin and Verapamil Together: Common Questions

Can you take Quercetin with Verapamil?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 4 interactions listed for Quercetin and Verapamil?
Verapamil belongs to more than one drug category, and Quercetin interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Quercetin and Verapamil interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Verapamil and Quercetin?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.