Herb & supplement monograph

Red Clover Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Red Clover interacts with medications. The heart of this page is the interaction list — every drug Red Clover is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Red Clover is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Red Clover Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Red Clover drug interaction appears low for most people. None of the listed interactions are rated major, and the great majority are minor with little or no evidence of a real effect in people.

Interactions deserving the most attention

The concerns we weigh most heavily involve hormone-related medicines. Because red clover contains plant compounds that can act like weak estrogen, it may interfere with estrogen therapy, and it could work against tamoxifen, so we suggest people on tamoxifen avoid it until more is known. There is also one report of a person on methotrexate who developed toxicity symptoms after starting red clover, which resolved once it was stopped.

What the rest of the list means

The long list of interacting medications looks alarming, but most entries are theoretical, based on lab findings that red clover might affect enzymes the body uses to clear certain drugs. When these predictions were tested in small human studies, red clover did not change how those medications were handled, and studies also have not confirmed the blood-thinning effect once suspected from its coumarin content.

Check your medications against Red Clover

Based on HelloPharmacist’s Red Clover interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Red Clover

869 medications have a known interaction with Red Clover, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Red Clover using our pharmacist-reviewed interaction data.

AI summaries are generated from our Red Clover interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Red Clover combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Red Clover affects

Every type of medication (drug category) Red Clover is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 9 drug categories Red Clover interacts with

EstrogensMethotrexate (trexall, Others)Tamoxifen (nolvadex)Anticoagulant/antiplatelet DrugsCaffeineCytochrome P450 1a2 (cyp1a2) SubstratesCytochrome P450 2c19 (cyp2c19) SubstratesCytochrome P450 2c9 (cyp2c9) SubstratesCytochrome P450 3a4 (cyp3a4) Substrates

Estrogens

Theoretically, concomitant use of large amounts of red clover might interfere with estrogen therapy.
Red clover contains phytoestrogens which might have estrogenic activity in some people. Theoretically, red clover might compete for estrogen receptors and interfere with estrogen-containing drug therapy.

Likelihood Probable Evidence D

Methotrexate (Trexall, Others)

Theoretically, red clover might increase the risk of methotrexate toxicity.
In a case report, a 52-year-old female receiving weekly methotrexate injections for psoriasis developed symptoms of methotrexate toxicity, including severe vomiting and epigastric pain, after three days of taking red clover 430 mg daily. Toxicity resolved after red clover was discontinued. However, no liver function tests or methotrexate levels were reported.

Likelihood Possible Evidence D

Tamoxifen (Nolvadex)

Theoretically, the phytoestrogens in red clover might interfere with tamoxifen.
In vitro and animal research suggests that genistein, a constituent of red clover, might antagonize the antitumor effects of tamoxifen. However, there is some evidence from an animal study that red clover does not reduce the efficacy of tamoxifen. Until more is known, tell patients taking tamoxifen to avoid red clover.

Likelihood Possible Evidence D

Anticoagulant/Antiplatelet Drugs

Although some laboratory research suggests that red clover may have anticoagulant and antiplatelet activity, clinical research has not shown this effect.
In vitro research suggests that genistein in red clover has antiplatelet effects, and historically, red clover was thought to have anticoagulant effects due to its coumarin content. However, some experts state that this is unlikely as most natural coumarins have not been shown to have anticoagulant effects, and their content in red clover is low. Additionally, some clinical research in postmenopausal patients found no effect on coagulation or prothrombin time with the use of red clover flowering tops 378 mg daily for 12 months or red clover isoflavone (Rimostil) 50 mg daily for 2 years.

Likelihood Unlikely Evidence B

Caffeine

Theoretically, soy might reduce the clearance of caffeine; however, a small clinical study found no effect.
Red clover contains genistein. Taking genistein 1 gram daily for 14 days seems to inhibit caffeine clearance and metabolism in healthy females. However, this effect does not seem to occur with the lower amounts of genistein found in red clover. A clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of caffeine.

Likelihood Unlikely Evidence D

Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, red clover might increase levels of drugs metabolized by CYP1A2; however, a small clinical study found no effect.
In vitro evidence shows that red clover inhibits CYP1A2. However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of caffeine, a CYP1A2 probe substrate.

Likelihood Unlikely Evidence D

Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, red clover might increase the levels and clinical effects of drugs metabolized by CYP2C19.
In vitro evidence suggests that red clover weakly inhibits CYP2C19. This interaction has not been reported in humans.

Likelihood Unlikely Evidence D

Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, red clover might increase levels of drugs metabolized by CYP2C9; however, a small clinical study found no effect.
In vitro evidence suggests that red clover might inhibit CYP2C9. However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of tolbutamide, a CYP2C9 probe substrate.

Likelihood Unlikely Evidence D

Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, red clover might increase levels of drugs metabolized by CYP3A4; however, a small clinical study found no effect.
In vitro evidence shows that red clover might inhibit CYP3A4 isoenzymes. However, a clinical study in healthy postmenopausal individuals shows that taking red clover capsules standardized to contain 60 mg isoflavones twice daily for 14 days does not affect the pharmacokinetics of alprazolam, a CYP3A4 probe substrate.

Likelihood Unlikely Evidence B

Monograph

Red Clover: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Red clover is a plant rich in isoflavones (plant compounds with weak estrogen-like activity) that is most often used for menopause symptoms like hot flashes. The evidence is mixed and generally weak, with some studies showing modest benefit and others showing none. Because of its hormone-like effects, it's not for everyone—talk with your pharmacist or doctor before trying it, especially if you have a hormone-sensitive condition.

Scientific name: Trifolium pratense
Family: Fabaceae
Part used: Flowering tops (blossoms) and aerial parts
Common forms: Capsules, tablets, standardized extracts, tinctures, teas, and topical preparations

People commonly use it for

Menopause symptoms (hot flashes)
High cholesterol
Bone health/osteoporosis
Skin and hair concerns
Women's health

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally well tolerated short-term in healthy adults, but its estrogen-like activity calls for caution in certain people.

PregnancyLikely Safe

When used orally in amounts commonly found in foods.

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in amounts commonly found in foods.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Red clover (Trifolium pratense) is a perennial flowering plant in the legume family. It is native to Europe and Asia but now grows widely across North America and other parts of the world, often in fields and meadows. Its pinkish-purple flower heads are the part most often used in supplements.

Red clover has a long history in traditional medicine. Today it is best known as a source of isoflavones—plant compounds (including genistein and daidzein) that can act somewhat like the hormone estrogen in the body. Because of this, it is most commonly marketed for women's health, especially menopause symptoms. It comes in capsules, tablets, teas, tinctures, and standardized extracts.

How it works

Red clover's main active compounds are isoflavones, a type of phytoestrogen ("plant estrogen"). These include genistein, daidzein, formononetin, and biochanin A. Phytoestrogens have a chemical shape similar to estrogen and can attach weakly to estrogen receptors in the body.

Because of this, isoflavones may produce mild estrogen-like effects, which is the proposed reason they might ease menopause symptoms or influence bone and heart health. The effects are generally much weaker than the body's own estrogen.

It's important to know that much of what we understand about how red clover works comes from laboratory and animal research. How strongly these effects apply to people taking supplements is still uncertain.

Effectiveness

Does Red Clover work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 8 uses evaluated

8 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Red Clover, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 8 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Androgenic alopecia