Category: Herbs & Ingredients
Chamomile carries a bleeding-risk caution alongside warfarin and other blood thinners, but the human evidence behind it is thin: a small number of case reports, not a clinical trial. Here is what that caution is actually built on, and what it means if you take an anticoagulant.
Category: Herbs and Ingredients | Reading time: ~12 min | Level: Beginner
Chamomile tea has such a mild, bedtime reputation that the warning attached to it on warfarin can feel out of proportion, a flower in a teacup somehow filed next to a prescription blood thinner. It is a fair reaction to have, and it deserves a fair answer rather than a blanket "avoid it" or a shrug. The honest answer sits in the middle: there is a real biological reason for the caution, and there is very little clinical evidence actually behind it, and both of those things can be true at once.
This article sets out exactly what is known, where it comes from, and how thin or solid each piece of it actually is, so that anyone on warfarin or another blood thinner can make an informed choice rather than reacting to a warning label without knowing what stands behind it.
Chamomile, botanically Matricaria chamomilla, contains a mix of volatile oils, flavonoids and hydroxycoumarins, plant compounds chemically related to the coumarin family that also gives warfarin its name and its blood thinning mechanism [2]. That shared chemistry is the reason a bleeding-risk caution exists at all: a coumarin-containing plant, combined with a coumarin-derivative drug, is a plausible additive-effect concern on paper.
What that concern is not, at least so far, is a demonstrated effect confirmed by a clinical trial. The evidence that exists sits almost entirely at the level of published case reports, individual patient accounts written up because something notable happened, not controlled studies designed to measure whether chamomile changes bleeding risk in a group of people on warfarin.
The clearest piece of evidence is a single case report published in the Canadian Medical Association Journal in 2006. It describes a 70 year old woman on long term warfarin who was admitted with multiple internal haemorrhages after using chamomile tea and a chamomile skin lotion together [1]. The authors themselves noted, at the time, that no prior case like it had been documented. It remains, decades later, the most cited example behind this caution.
A separate review article on herb-warfarin interactions lists Matricaria chamomilla among the herbs associated with reported severe bleeding events in patients taking warfarin [5], which shows the concern has been noted more than once, though it is drawing on the same thin pool of case-level evidence rather than adding independent trial data.
NCCIH's own summary is careful and appropriately hedged: "Interactions between chamomile and some drugs metabolized by the liver and warfarin (a blood thinner) have been reported" [2]. Note the word "reported," not "demonstrated" or "confirmed in trials." That distinction matters and this article is keeping it deliberately.
The European Medicines Agency's herbal monograph on chamomile, which reviews chamomile's registered uses and safety data for a European regulatory audience, does not list warfarin in its interactions section at all [3]. It does flag a different, unrelated interaction: in patients who had undergone a kidney transplant and were taking high oral doses of chamomile for roughly two months, interactions based on effects on the CYP450 liver enzyme system were reported [3]. That is a different population, a different mechanism, and not a warfarin bleeding signal specifically, but it is a useful data point on its own: oral chamomile, taken in high, sustained doses, is not proven to be interaction free even setting the coumarin question aside.
Taken together, the evidence for a chamomile and warfarin bleeding interaction is best described honestly as theoretical to anecdotal: a real, biologically plausible mechanism, backed by a small number of case reports rather than trial data, noted by some reviewers and not listed as a formal interaction by at least one major regulator. That is not nothing, and it is not proof either.
| Scenario | What the literature suggests | What to do | |---|---|---| | Occasional chamomile tea, no anticoagulant medication | No documented bleeding concern in this group | No specific precaution needed | | Regular chamomile tea or supplement use, on warfarin | A documented case report of serious bleeding in this exact combination; theoretical coumarin-based additive risk | Mention your chamomile use to the prescriber managing your warfarin, especially if your INR has been unstable | | Chamomile used topically (creams, lotions, compresses), on warfarin | The main case report involved combined oral and topical use; the EU monograph lists no interactions for topical use alone | Lower concern than oral use, but disclose extensive or prolonged topical use to your prescriber if you are on warfarin | | Chamomile alongside aspirin, clopidogrel or a direct oral anticoagulant (not warfarin) | No comparable published case series exists for these specific drugs; the same coumarin-based plausibility applies in principle | Mention chamomile use to your prescriber as routine disclosure, even though the specific published evidence is thinner here | | Any anticoagulant medication, upcoming surgery | Standard pre-operative practice flags herbs with plausible bleeding associations, chamomile among them | Disclose chamomile use to your surgical team during pre-operative assessment, alongside all other supplements |
If you are not on a blood thinner, none of this changes anything about an occasional cup of chamomile tea. The caution in this article is specifically for people taking warfarin or another anticoagulant.
If you are on warfarin and you drink chamomile tea regularly, or use a chamomile supplement, the sensible step is simple disclosure: tell the prescriber or clinic that manages your warfarin. This is not because the evidence proves a dangerous interaction. It is because the evidence is thin enough that nobody can rule one out either, and mentioning it costs you nothing while giving your prescriber useful context if your INR ever comes back unexpectedly high.
Before any surgery, mention chamomile alongside every other supplement you take, the same way you would disclose any herb with a plausible bleeding association. Surgical teams are used to this conversation and would rather hear about it than not.
If you notice unusual bruising, bleeding gums, blood in urine or stool, or any other bleeding sign while regularly using chamomile alongside an anticoagulant, treat it as a reason to contact your prescriber promptly rather than waiting for your next scheduled blood test.
The chamomile and warfarin caution is real in the sense that it has a plausible chemical basis and at least one well documented case behind it, but it is not established in the sense of proven, quantified risk from clinical trials. The honest position is caution by prudence: disclose regular chamomile use to your anticoagulant prescriber, mention it before surgery, and do not treat a single historic case report as a guarantee that it will happen to you, or as proof that it cannot.
Anyone managing warfarin or another anticoagulant already has a relationship built around monitoring and small adjustments. Chamomile use is exactly the kind of detail worth adding to that ongoing conversation rather than deciding alone, particularly since the evidence is too thin for a firm yes or no answer from a website or a supplement label.
Chamomile earns its place in the Remedy Library for its evidence on sleep quality, which is moderate but genuine across more than one meta-analysis, and it is presented there with its cautions attached, including this one, rather than tucked away. The Chamomile Sleep Tea is a structure and function product: chamomile is associated with supporting relaxation and sleep quality, not a treatment for any diagnosed condition, and it is not positioned as compatible or incompatible with anticoagulant medication without your prescriber's input.
Remy, the PlantRx assistant, can surface published cautions like this one, including how thin or solid the underlying evidence actually is, and point you back to your prescriber for anything that touches a medication they manage.
Pregnant, breastfeeding, or on medication? Check with a healthcare professional first.
Chamomile carries a formal contraindication for anyone with hypersensitivity to it or to other plants in the daisy family, Asteraceae, which includes ragweed, chrysanthemums and marigolds, since cross reactivity and, rarely, severe allergic reactions including anaphylaxis have been documented [2][3]. On the liver, chamomile has a genuinely clean record: LiverTox rates it at the lowest likelihood score on its hepatotoxicity scale, describing it as an unlikely cause of clinically apparent liver injury despite widescale use [4]. Chamomile tea preparations are considered established as safe in pregnancy and lactation by the EU monograph, though extract and tincture preparations are not recommended in pregnancy due to insufficient safety data [3].
1. Segal R, Pilote L (2006). Warfarin interaction with Matricaria chamomilla. Canadian Medical Association Journal, 174(9):1281 to 1282. PMID 16636327. Case report, single patient on long term warfarin with multiple internal haemorrhages after combined oral and topical chamomile use. 2. National Center for Complementary and Integrative Health (NCCIH). Chamomile. Government evidence and safety review. nccih.nih.gov/health/chamomile. 3. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). European Union herbal monograph on Matricaria recutita L., flos. EMA/HMPC/55843/2011, adopted 7 July 2015. Regulatory herbal monograph. 4. National Institute of Diabetes and Digestive and Kidney Diseases, LiverTox. Chamomile (NBK548163). Government safety monograph, likelihood score E. 5. Milić N, Milošević N, Goločorbin Kon S, et al. (2014). Warfarin Interactions with Medicinal Herbs. Natural Product Communications 9(8). PMID 25233607. Review article, lists Matricaria chamomilla among herbs with reported bleeding events on warfarin.
There is no clinical trial showing chamomile tea causes bleeding problems on warfarin, but there is a published case report of a serious bleeding event in a warfarin patient who used chamomile tea and a chamomile lotion together. Given how easy it is to avoid, mentioning your chamomile habit to the prescriber who manages your warfarin is a sensible, low cost precaution rather than an overreaction.
Chamomile contains coumarin type compounds, the same broad chemical family that gives warfarin its name and its blood thinning action. That shared chemistry is the biological reason a bleeding-risk caution exists, even though the human evidence for a real world effect at typical tea or supplement doses is limited to case reports rather than trials.
Honestly, thin. The main published evidence is a single detailed case report describing a warfarin patient with multiple internal haemorrhages after using chamomile products, plus a review article that lists chamomile among herbs associated with reported bleeding events on warfarin. That is case-report and review level evidence, not trial evidence, and it should be described that way rather than overstated.
Not by name. The EU herbal monograph on chamomile does not list warfarin in its interactions section. It does note a separate interaction, based on effects on a liver enzyme system, reported in kidney transplant patients taking high oral doses of chamomile for about two months, which is a different population and a different mechanism, but it does illustrate that oral chamomile is not interaction free at high, prolonged doses.
Yes, and this is worth stating plainly since it is not true of every botanical with an interaction caution. The US LiverTox database rates chamomile at its lowest hepatotoxicity likelihood score, describing it as an unlikely cause of clinically apparent liver injury despite widescale use.
This is worth raising with your surgical team as part of routine pre-operative medication and supplement disclosure, the same as any herbal product with a theoretical bleeding association. Surgical teams commonly ask patients to pause certain herbs before procedures out of caution, and chamomile's coumarin content is a reasonable enough basis for that same conversation, even with limited trial evidence behind it.
The published case reports and reviews focus specifically on warfarin, and there is not a comparable documented case series for aspirin, clopidogrel or the newer direct oral anticoagulants. The same coumarin based biological plausibility applies broadly to anything that affects clotting, so the same prudent disclose-to-your-prescriber approach makes sense even where the specific published case evidence is thinner still.
No. One case report describing a bleeding event does not mean chamomile tea is established as dangerous on warfarin, and the evidence here sits at the level of caution by prudence rather than a proven, quantified risk. The sensible move is simply to mention your chamomile habit at your next warfarin review so it is on record and your prescriber can factor it in if your INR ever needs explaining.
Because a plausible chemical mechanism, chamomile's coumarin content, lines up with a real, if rare, documented event, and blood thinner interactions carry a high enough cost if wrong that regulators and clinicians tend to flag plausible risks even before trial evidence catches up. That is a reasonable, precautionary basis for a caution. It is not the same as proof, and this article says so rather than dressing the case report up as settled science.
The clearest case report actually involved both chamomile tea and a chamomile skin lotion used together, so it is difficult to separate the contribution of each from that single case. The EU monograph lists no interactions for chamomile used topically as a general matter. Given the uncertainty, treating any concentrated, repeated topical chamomile use with the same mild caution as oral use is the more careful reading, without overstating it as an established risk on its own.