The short answer
Feverfew may affect clotting, so it deserves caution during warfarin treatment. The inspected evidence does not establish a clinical bleeding rate for the exact combination. Laboratory platelet studies and a bleeding case without warfarin support a concern, but they are not a direct warfarin-feverfew interaction trial.
What this answer covers
Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures.
- Supplement or preparation
- Feverfew
- Medication ingredient
- warfarin
What does the evidence show?
A primary laboratory experiment found that feverfew extracts inhibited platelet aggregation and secretion. A later case described prolonged vaginal bleeding and abnormal coagulation tests during high-dose feverfew use, with improvement after stopping it and receiving treatment. The patient was not taking warfarin, and several treatments changed during recovery. These observations cannot quantify an added warfarin risk, but they explain the precaution. NCCIH also notes that feverfew may slow clotting.
Which forms and conditions matter?
Leaves, flower preparations, extracts and standardized products vary in constituent content. A cell experiment involving extract cannot be converted directly into a human capsule dose. The case's high exposure cannot establish a safe lower dose or prove equivalent risk from another preparation. The exact botanical species should be checked rather than relying on the common word feverfew.
What should I discuss with my care team?
Ask the anticoagulation clinician or pharmacist to assess feverfew before co-use, especially if there is a bleeding history or a planned procedure. Provide the product label and all other medicines. The evidence does not establish that taking it at a different time from warfarin prevents possible platelet effects. Do not change anticoagulant treatment or create a tapering plan from this article.
How certain is the answer?
Targeted review found indirect mechanism and supplement-only clinical evidence, not an inspected controlled study of the exact pair. Absence of a direct trial does not prove safety. This finding therefore describes a possible additive risk with very low certainty rather than presenting an established bleeding increase as if it had been measured in warfarin users.
Evidence and practical considerations
Side effects & toxicity
Feverfew may affect clotting, so it deserves caution during warfarin treatment. The inspected evidence does not establish a clinical bleeding rate for the exact combination. Laboratory platelet studies and a bleeding case without warfarin support a concern, but they are not a direct warfarin-feverfew interaction trial.
- Exact scope
- Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures. with Oral warfarin, including warfarin sodium tablets with the warfarin active moiety.
- Medication form and route
- oral warfarin
- Timing or duration
- Study-specific durations are described in each source exposure; no universally safe exposure duration has been established.
What remains uncertain
- Targeted review found indirect mechanism and supplement-only clinical evidence, not an inspected controlled study of the exact pair. Absence of a direct trial does not prove safety. This finding therefore describes a possible additive risk with very low certainty rather than presenting an established bleeding increase as if it had been measured in warfarin users.
Factors that may matter: Exact supplement preparation and other ingredients; Starting, stopping or changing supplement intake; Baseline anticoagulation control and clinician-supervised monitoring.
Read the supporting source summaries
Source 1: current U.S. regulatory prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral warfarin sodium tablets.
The label advises closer INR monitoring when botanicals are started or stopped, identifies variable botanical composition and lists selected potential interactions. Vitamin K intake should remain consistent.
How this applies: Oral warfarin sodium has warfarin as its active moiety. Label-level botanical and vitamin K monitoring advice applies; it is not proof of this exact supplement effect. Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures.
Regulatory precautions do not quantify the incidence for every exact preparation or prove an interaction for an unlisted ingredient. Warfarin sodium is bridged to the warfarin active moiety only for the oral product.
Source 2: laboratory platelet study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Blood platelets and polymorphonuclear leukocytes studied experimentally.
The extracts inhibited platelet aggregation and release of serotonin in response to several stimuli.
How this applies: Feverfew platelet experiments without warfarin. Supports biological plausibility rather than a measured clinical interaction. Exact package scope: Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures.
In-vitro exposure, not oral feverfew plus warfarin in patients. Does not quantify bleeding risk or translate into a safe dose.
Source 3: peer-reviewed human case report
europepmc.org · Source check Sep 10, 2026
Population: One 36-year-old woman; warfarin was not among her reported medicines.
Vaginal bleeding and prolonged coagulation tests were reported. Recovery followed feverfew withdrawal together with other treatment.
How this applies: General warfarin monitoring guidance applies to this pair; the exact-pair conclusion relies on the source-specific evidence and limitations below. Exact package scope: Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures.
No warfarin exposure, one uncontrolled case, concurrent treatment and uncertain causal attribution. This is a supplement safety signal, not direct evidence for a warfarin pair.
Source 4: government clinical reference
nccih.nih.gov · Source check Sep 10, 2026
Population: People taking feverfew products.
The reference states that feverfew may slow blood clotting and gives a surgery-related precaution.
How this applies: General warfarin monitoring guidance applies to this pair; the exact-pair conclusion relies on the source-specific evidence and limitations below. Exact package scope: Oral Tanacetum parthenium with oral warfarin. American feverfew, Parthenium integrifolium, is a different plant; topical use and isolated parthenolide are separate exposures.
Not a direct warfarin interaction study; it does not establish the frequency or size of a combined-use risk.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Original evidence and contradictory findings assessed for this exact pair. Article drafted and existing statements adjudicated. Clinical sign-off has not been recorded. | |
| Research summary published |
Article revision: 5f3aea5919aba1b4
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.