Herbs and Blood Thinners: Warfarin, Anticoagulants and Bleeding Risk
Which herbs have been linked to bleeding or changed warfarin effects, what NCCIH, MedlinePlus, the NHS and a systematic review say, and who to call: your anticoagulation clinic or pharmacist.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Bleeding that will not stop, vomiting or coughing up blood, or a sudden bad headache with confusion or slurred speech needs urgent help. In the US call 911. The NHS lists these among the signs of serious bleeding on warfarin. [1][2] If you take a blood thinner and notice unexplained bruising, nosebleeds, or blood in your urine or stool, contact your prescriber or anticoagulation clinic promptly. [1] Do not stop a blood thinner on your own.
Whether a combination is dangerous for you depends on your medicine, your blood tests and your health. Your anticoagulation clinic, prescriber or pharmacist is the right contact. This page cannot tell you what is safe for you.
What the sources found
| Herb or product | What the source found | Source type and strength |
|---|---|---|
| Ginkgo (Ginkgo biloba L.) [6] | May increase bleeding in people taking anticoagulants such as warfarin. [4] MedlinePlus lists it among herbal products that may interact with warfarin. [7] | NCCIH and MedlinePlus statements; a documented caution |
| Garlic supplements (Allium sativum L.) [8] | May increase the risk of bleeding. NCCIH says this is especially important before surgery or with anticoagulants or aspirin. [3] | NCCIH statement; a documented caution |
| St. John's wort | NCCIH lists warfarin among medicines it can weaken. [5] The NHS says not to take it with warfarin. [1] A systematic review also lists it among products with an increased bleeding risk, so sources describe the direction differently. [9] | NCCIH and NHS statements plus a review; the sources describe the direction differently |
| Chamomile | NCCIH says interactions with warfarin and some liver-processed drugs have been reported. [10] | Reported; details not given on that page |
| Echinacea, ginseng, goldenseal | Listed by MedlinePlus among herbal products that may interact with warfarin. [7] | Listing only; the reason is not given |
| Green tea, ginger, cranberry, Chinese wolfberry | Named in a systematic review as increasing bleeding risk when used with warfarin. [9] The NHS separately says to avoid cranberry juice and cranberry products on warfarin. [1] | Systematic review; many reports are case reports |
A systematic review that searched 5 databases up to the end of 2019 found 149 articles on 78 herbs, foods or supplements reported to interact with warfarin. [9] Twenty herbs and supplements were reported to cause bleeding, from minor events such as purpura and gum bleeding to major events such as intracranial bleeding that led to death. [9] Its authors say most food, herbs and supplements can be taken safely in moderation, but that patients should keep asking their healthcare professionals when starting anything new. [9]
Newer anticoagulants and aspirin
Proper evidence not found, in the sources we read, for herb interactions with the newer anticoagulants (those that are not warfarin). We read NCCIH single-herb pages, MedlinePlus, the NHS warfarin page and PubMed reviews. NCCIH names aspirin as a bleeding-related medicine for garlic. [3] Ask a pharmacist about your specific medicine. The page on supplements and blood thinners in our safety section covers more.Food and vitamin K
Warfarin is also affected by diet. MedlinePlus advises eating consistent amounts of vitamin K-containing foods from week to week. [7] The NHS says foods high in vitamin K can still be eaten, but to talk to your warfarin clinic, and to talk to your doctor before big diet changes. [1] The NHS also says not to take vitamin K supplements on warfarin. [1] Herbs and herbal teas are part of this picture, so tell your clinic about them.Surgery and dental work
NCCIH says certain dietary supplements may increase the risk of bleeding or affect response to anesthesia, and to tell your providers well ahead of an operation. [11] The NHS says warfarin patients should show their anticoagulant alert card to their doctor or dentist before any medical or dental procedure. [1] See herbs before and after surgery.Pregnancy and other situations
NCCIH says ginkgo may be unsafe in pregnancy and might cause early labor or extra bleeding during delivery if used near that time. [4] Warfarin itself is not usually used in pregnancy, per the NHS. [1] Ask your prescriber about both.What you can do
- Make a written list of every medicine, herb, tea and supplement and bring it to your anticoagulation clinic or pharmacist. MedlinePlus advises carrying such a list. [7] Our medicine and supplement worksheet can help.
- Ask before starting or stopping any herb, not after.
- Read the product label for the herb's scientific name and any added ingredients. See reading an herbal supplement label.
- Read the single-herb guides: ginkgo, garlic and St. John's wort.
Limits
Most of what we found is case reports and expert reviews, not controlled trials of each herb with each blood thinner. A herb in the table is not proven to cause bleeding in every user, and a herb missing from the table is not proven safe.Frequently asked questions
Which herbs should I avoid on warfarin?
We cannot give you a personal list. NHS advice is not to take St. John's wort or vitamin K supplements on warfarin. [1] MedlinePlus lists coenzyme Q10, echinacea, garlic, ginkgo, ginseng, goldenseal and St. John's wort as products that may interact. [7] Ask your anticoagulation clinic about each one.
Does garlic thin the blood?
NCCIH says taking garlic supplements may increase the risk of bleeding. [3]
Can I drink chamomile tea with warfarin?
NCCIH says interactions between chamomile and warfarin have been reported. [10] A systematic review also names chamomile tea. [9] Ask your clinic before drinking it regularly.
Should I tell my dentist about herbs?
Yes. The NHS tells people on warfarin to show their anticoagulant alert card to their doctor or dentist before procedures. [1] Tell them about herbs too.
Is aspirin a "blood thinner" for this purpose?
NCCIH mentions aspirin alongside anticoagulants when it warns about garlic and bleeding. [3] MedlinePlus also lists aspirin among nonprescription products that may interact with warfarin. [7]
References
- NHS (UK), Warfarin, page last reviewed 24 February 2026. Read 2026-10-23.
- Poison Control (National Capital Poison Center, US), poison.org. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), Garlic, last updated February 2025. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), Ginkgo, last updated February 2025. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), St. John's Wort, last updated May 2025. Read 2026-10-23.
- GBIF Secretariat, GBIF Backbone Taxonomy match for Ginkgo biloba: accepted name Ginkgo biloba L.. Read 2026-10-23.
- MedlinePlus, Warfarin, drug information page. Read 2026-10-23.
- GBIF Secretariat, GBIF Backbone Taxonomy match for Allium sativum: accepted name Allium sativum L.. Read 2026-10-23.
- Tan CSS, Lee SWH. Warfarin and food, herbal or dietary supplement interactions: a systematic review. British Journal of Clinical Pharmacology 2021; PubMed abstract. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), Chamomile, last updated November 2024. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH, US), Using Dietary Supplements Wisely, last updated January 2019. Read 2026-10-23.