What happens when you take warfarin with dong quai?
Warfarin is a vitamin K antagonist: it stops the liver from making fully functional clotting factors II, VII, IX, and X. Clinicians track its effect with the international normalised ratio (INR) and aim to keep it inside a target window for your condition. Dong quai is the root of Angelica sinensis, a plant in the parsley family used in traditional Chinese medicine for menopausal symptoms, menstrual cramps, and as a general 'blood tonic'. Putting the two together can push the INR higher than intended, increasing bleeding risk.
- Coumarin overlap. Dong quai root contains coumarin-family compounds, including ferulic acid and osthole. These are in the same chemical family as warfarin itself, so the herb can add more anticoagulant-type activity on top of the drug already at work.
- Antiplatelet effect. Dong quai constituents inhibit platelet aggregation in laboratory studies. That is a second possible bleeding mechanism, layered on top of warfarin's effect on the clotting cascade.
- A pharmacodynamic interaction. Animal studies show dong quai can prolong prothrombin time without changing the measured warfarin blood concentration. That suggests the effect adds up at the clotting cascade rather than simply raising drug levels, which makes it harder to predict from the warfarin dose alone.
Why is this important?
Dong quai is one of the few herbs where the bleeding signal is mechanistically plausible: its constituents are coumarins, the same chemical family as the drug, and it also affects platelets. Stacked on warfarin, the combination has more than one way to nudge bleeding risk up.
The published case is instructive because the patient had been stable on warfarin for years and the herb was the only change. Her INR drifted well above target and recovered only after she stopped the dong quai. A previously rock-solid INR drifting upward after a new herb is added is the classic clinical fingerprint of a herbal interaction.
Dong quai is marketed mainly to women for menopausal symptoms, menstrual concerns, and fertility — the same population often on warfarin for atrial fibrillation, a heart-valve replacement, or a prior blood clot. Risk is higher in older adults and in anyone also taking aspirin, NSAIDs, or other antiplatelet agents. It is worth being clear about the strength of evidence: this rests on a single human case report plus supportive animal data, not large trials, so the concern is real but not heavily documented.
What should you do?
The practical recommendation, supported by the case literature and standard anticoagulation guidance, is to avoid dong quai while on warfarin. The benefit for menopausal symptoms is modest, alternatives exist, and the bleeding signal is consistent in direction.
Before any change: If you are already taking dong quai and warfarin together, do not simply stop one on your own — tell the clinician who manages your anticoagulation first. Stopping the herb can swing the INR the other way, and they will want to plan an INR check around it.
Every day while the two overlap: Watch for bleeding warning signs and keep your supplement list current for every clinician and dentist you see. Be extra cautious if you also take aspirin, NSAIDs, or other antiplatelet drugs.
After any change (starting or stopping the herb, or a warfarin dose adjustment): Ask your anticoagulation clinic for an INR check soon after the change, and again once your dose has been steady for a few weeks, to confirm you are back in target range.
Stop the herb and contact your anticoagulation clinic the same day if you notice any bleeding warning sign: a nosebleed that will not stop, bleeding gums when brushing, pink or red urine, black or tarry stools, coffee-ground vomiting, large new bruises, a severe headache, sudden weakness or numbness, or any change in vision. Bleeding into the brain or gut is the worst case 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 on when to stop.
Which specific products are affected?
The 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.
Just as important are blends where dong quai is not on the front label. Many menopause-support formulas combine it with black cohosh, red clover, or soy isoflavones; multi-herb 'women's tonic' and 'blood tonic' formulas frequently include it too. Check the supplement facts panel and the full herbal ingredient list, not just the product name.
Dong quai is also simmered into soups in Chinese cooking. Culinary amounts are smaller than supplement servings, and no formal safety threshold has been established. The simplest approach for a warfarin patient is to avoid both supplemental and culinary dong quai.
The science behind it
The central reference is a single human case report: Page & Lawrence, Potentiation of warfarin by dong quai (Pharmacotherapy, 1999; PMID 10417036). A woman who had been stable on warfarin for years added dong quai for menopausal symptoms; within weeks her INR rose well above her target range, and it returned to normal after she stopped the herb. Because it is a single case, it strongly suggests a real effect but cannot establish how often or how severely it occurs.
Supporting mechanistic and animal data are summarised in a review of warfarin–Chinese-herb interactions (PMC4325561), which documents dong quai's coumarin content and animal pharmacodynamic findings — prolonged prothrombin time without a change in warfarin blood levels. That is the extent of the direct evidence: one human case plus animal/laboratory support. There are no large clinical trials of this combination.
Frequently Asked Questions
Can I take dong quai if my INR is well controlled?
Even a stable INR can drift after a new herb is added — that is exactly what the case report describes. The safest course on warfarin is to avoid dong quai rather than rely on a currently good INR.
I already took some dong quai. What should I do?
Do not panic and do not abruptly stop everything on your own. Tell the clinician who manages your warfarin, ask whether you need an INR check, and watch for any unusual bleeding. Report bleeding warning signs the same day.
Is the cooking amount in soup a problem?
Culinary amounts are smaller than supplement servings, but no safe threshold has been set for warfarin patients. To keep things simple, it is reasonable to avoid dong quai in food as well while on warfarin.
How strong is the evidence for this interaction?
It rests on one published human case report plus supportive animal and laboratory data. The direction of effect is plausible and consistent, but it has not been studied in large trials, so the exact risk is not well quantified.
Are other 'women's health' herbs a concern too?
Dong quai is the specific concern here, but it often appears in menopause and 'blood tonic' blends alongside other herbs. Always check the full ingredient list and discuss any new supplement with your pharmacist before adding it to warfarin.
Will stopping dong quai fix my INR?
In the reported case the INR returned to normal after the herb was stopped. But because stopping can move the INR the other way, do it in coordination with your anticoagulation clinic and with an INR check, not on your own.
Key takeaways
- Dong quai contains coumarin-family compounds and has antiplatelet activity, giving it more than one plausible way to amplify warfarin's effect.
- A published case report shows a previously stable patient's INR rising above target after adding dong quai and recovering after stopping it — but this is a single case plus animal data, not large trials.
- If you take warfarin, avoid dong quai, including hidden dong quai in menopause and 'blood tonic' blends.
- If you have been taking both, do not stop either abruptly — tell your anticoagulation clinic and arrange an INR check around any change.
- Treat any unusual bleeding as urgent, and review every supplement with your doctor or pharmacist.