What happens when you take warfarin with dong quai?
Warfarin is a vitamin K antagonist that prevents the liver from producing functional clotting factors II, VII, IX, and X. The international normalised ratio (INR) is the test clinicians use to keep the effect inside a safe window, typically 2.0-3.0 for atrial fibrillation and most clot-prevention indications.
Dong quai is the root of Angelica sinensis, a plant in the parsley family widely used in traditional Chinese medicine for menopausal symptoms, menstrual cramps, and as a general 'blood tonic'. Chemically it is loaded with coumarin derivatives, including ferulic acid and osthole. Coumarin compounds are structurally related to warfarin itself, which is one reason the interaction concern is so direct. In addition, dong quai constituents inhibit platelet aggregation in laboratory studies, adding a second mechanism of bleeding risk.
The most-cited case in the medical literature is Page & Lawrence (Pharmacotherapy, 1999). A 46-year-old woman with atrial fibrillation had been stable on warfarin for years. She added dong quai 565 mg once or twice daily for menopausal symptoms. Within four weeks her INR rose from a stable target to 4.9, a level at which spontaneous bleeding risk climbs sharply. INR returned to normal about one month after she stopped the dong quai. Animal pharmacokinetic studies have since shown that dong quai significantly prolongs prothrombin time without changing warfarin blood concentration, consistent with a pharmacodynamic (additive) interaction in addition to any pharmacokinetic effect.
Why is this important?
Dong quai is one of the few herbs where the interaction signal is mechanistically obvious. Its active constituents include coumarins, the same chemical family as the drug. Stacked on top of warfarin's effect on the coagulation cascade, plus its antiplatelet effect, the combination has more than one way to increase bleeding.
The Page & Lawrence case is also instructive because the patient had been stable on warfarin for years. The herb was the only change. INR doubled within a month and recovered only after the herb was discontinued. That pattern, of a previously rock-solid INR suddenly drifting up, is the classic clinical fingerprint of a new herbal interaction.
Dong quai is commonly marketed for women going through menopause and for menstrual or fertility concerns. Patients who are simultaneously on warfarin for atrial fibrillation, valve replacement, or prior venous thromboembolism are exactly the demographic most likely to encounter both. The risk is higher in older adults and in anyone also taking aspirin, NSAIDs, or other antiplatelet agents.
What should you do?
The straightforward recommendation, supported by both the case literature and standard anticoagulation guidance, is to avoid dong quai while on warfarin. The benefit for menopausal symptoms is modest, alternative options exist, and the bleeding signal is consistent.
If you are already taking dong quai and warfarin together, do not just stop one without telling the clinician who manages your anticoagulation. Stopping the herb can swing the INR the other way. Ask for an INR check within 1-2 weeks of any change and again 2-4 weeks after a new dose is steady.
Stop the herb and contact your anticoagulation clinic the same day if you notice any bleeding warning sign: a nosebleed lasting more than 10 minutes, bleeding gums when brushing, pink or red urine, black or tarry stools, coffee-ground vomiting, large new bruises, severe headache, sudden weakness or numbness, or any change in vision. Bleeding inside the brain or gut is the worst-case scenario and time matters.
Before any elective surgery, dental procedure, or biopsy, tell the team about every supplement you take, including dong quai, and follow their instructions about when to stop.
Which specific products are affected?
The interaction concern covers dong quai in all common forms: capsules of dried Angelica sinensis root, standardised dong quai extracts, liquid tinctures, and the traditional decoctions used in Chinese herbal medicine. Many menopause-support blends sold over the counter list dong quai alongside black cohosh, red clover, or soy isoflavones. Check the supplement facts panel and the herbal ingredient list. Multi-herb 'women's tonic' and 'blood tonic' formulas often contain dong quai even when it is not in the product name.
Dong quai is sometimes used in cooking in Chinese cuisine, typically simmered in soups. Culinary amounts are much smaller than supplement doses, but no formal safety threshold has been established. To be safe, the simplest approach for a warfarin patient is to avoid both supplemental and culinary preparations of dong quai.
The bottom line
Dong quai contains coumarin-family compounds and has antiplatelet activity. The published case report shows it can roughly double the INR within four weeks in a previously stable warfarin patient. Avoid dong quai while on warfarin. If you have been taking it, tell your anticoagulation team before changing anything, schedule INR checks, and treat any unusual bleeding as urgent.