What happens when you take warfarin with danshen?
Warfarin is a blood thinner used to prevent clots in conditions such as atrial fibrillation, after a mechanical heart-valve replacement, and after a deep-vein clot or pulmonary embolism. It works by slowing the liver's production of several clotting factors. Its effect is tracked with a blood test called the INR, which is kept inside a carefully controlled window so the blood is thin enough to prevent clots but not so thin that it bleeds.
Danshen is the dried root of Salvia miltiorrhiza, one of the most widely used herbs in traditional Chinese medicine for heart and circulation problems. The interaction with warfarin happens in two ways at once:
- It raises warfarin levels. Pharmacokinetic studies show danshen slows the body's clearance of warfarin and lets more of it accumulate. More warfarin in the blood means a stronger blood-thinning effect.
- It thins the blood on its own. Compounds in danshen inhibit platelet aggregation and have antithrombotic activity in laboratory models. This effect stacks on top of warfarin rather than overlapping with it.
- The two effects combine. Because danshen both increases warfarin's level and adds its own anticoagulant action, the overall blood-thinning effect can climb quickly and unpredictably. A controlled clinical trial found that co-administration significantly prolonged clotting times compared with warfarin alone.
In published case reports, the consequences have been severe: patients who added danshen to warfarin developed dangerously high INRs and serious bleeds, including bleeding into the chest cavity (haemothorax), within roughly two weeks of starting the herb.
Why is this important?
This is one of the highest-confidence, highest-severity herb-warfarin interactions in the medical literature. A few features set it apart from milder interactions.
The mechanism is multi-layered. Danshen pushes warfarin levels up and also adds its own antiplatelet and antithrombotic action. When both arms of an interaction work together, the magnitude is usually larger and the effect can appear faster.
The reported harms are real bleeds, not just lab numbers. Case reports describe bleeding into the chest cavity, gastrointestinal bleeding, and other major bleeds. A severely over-thinned blood state carries a steep risk of spontaneous, serious bleeding, and danshen has demonstrably driven patients there.
The people most likely to combine them are the most vulnerable. Danshen is usually reached for precisely because someone has heart disease. The classic scenario is a person with atrial fibrillation or a mechanical valve who picks up a "natural" heart-support product. That is the worst possible overlap, because the reason they are on warfarin already means they can afford neither a clot nor a major bleed.
What should you do?
Before starting or changing anything: Do not start a danshen product while you are on warfarin. If you are considering any traditional Chinese medicine heart formula, review the full ingredient list with your doctor or pharmacist first, because danshen is often one of several herbs in a blend.
If you have already started danshen: Contact your anticoagulation clinic now and arrange an INR check as soon as possible, ideally the same day. Do not stop your warfarin on your own. Over-thinned blood needs to be managed with clinical guidance, sometimes with specific reversal treatment, and stopping warfarin yourself can swing your INR the wrong way.
Every day, while any change settles: Watch for warning signs of bleeding and treat them as urgent: chest pain or sudden shortness of breath (which can signal bleeding into the chest), severe headache, new weakness or vision change, vomiting blood or coffee-ground material, black tarry stools, pink or red urine, a nosebleed that will not stop, or large unexplained bruises. Any of these warrant immediate medical attention.
After any change, and before procedures: If you and your clinician decide to stop danshen, expect your INR to be monitored more closely for a while, because removing the herb can also move your INR. Before any planned procedure, including dental work, tell the whole team you have been using danshen so they can coordinate stopping it safely, typically a week or two in advance.
Which specific products are affected?
The warning covers danshen in every form, including dried Salvia miltiorrhiza root, decoctions (boiled water extracts), capsules of powdered root, standardised tanshinone extracts, salvianolic acid extracts, and sublingual or dissolvable danshen tablets.
It also covers traditional Chinese medicine cardiovascular formulas that include danshen as a component. Branded examples include Compound Danshen Dripping Pills (Fufang Danshen Diwan) and danshen tablets. Many multi-herb heart blends list danshen alongside notoginseng (san qi), borneol, or other herbs, so check the full herbal ingredient panel.
Danshen is not used in cooking, so there is no everyday culinary amount to compare against, as there is with garlic, ginger, or turmeric. Any deliberate intake of danshen, whether as a single herb or inside a blend, is the concern.
The science behind it
The evidence here is unusually consistent for an herb-warfarin interaction, drawing on case reports, a controlled trial, and mechanistic studies.
- Chan TYK. Interaction between warfarin and danshen (Salvia miltiorrhiza). Ann Pharmacother. 2001;35(4):501-504. A review summarising case reports of gross over-anticoagulation in patients who added danshen to warfarin, including a man who developed bleeding into the chest cavity with a very high INR about two weeks after starting daily danshen. PMID 11302416.
- Chua YT, Ang XL, Zhong XM, Khoo KS. Interaction between warfarin and Chinese herbal medicines. Singapore Med J. 2015;56(1):11-18. A review pooling the danshen case reports, a controlled clinical trial showing prolonged clotting times during co-administration, and pharmacokinetic studies showing reduced warfarin clearance. Available at https://pmc.ncbi.nlm.nih.gov/articles/PMC4325561/.
Frequently Asked Questions
Is it ever safe to take danshen with warfarin?
There is no established safe way to combine them. The interaction is strong, well-documented, and has caused serious bleeds. The safest approach is to avoid danshen entirely while on warfarin.
I took one dose of danshen by accident. What now?
Contact your anticoagulation clinic or pharmacist and tell them what you took and when. They can advise whether you need an earlier INR check and what bleeding signs to watch for. Do not change your warfarin yourself.
What are the most urgent warning signs?
Chest pain or sudden breathlessness can signal bleeding into the chest and need emergency assessment. Other red flags include a severe headache, new weakness or vision change, vomiting blood, black tarry stools, or blood in the urine.
Can I just lower my warfarin dose to make room for danshen?
No. The interaction is large and unpredictable, and trying to balance warfarin against the herb is far riskier than simply avoiding danshen. Any dose decisions should be made only by your anticoagulation clinic.
Does this apply to TCM heart formulas that contain danshen?
Yes. Danshen is frequently one ingredient in a multi-herb cardiovascular blend, so check the full ingredient list. If danshen is present, the same warning applies.
What if I stop danshen after taking it for a while?
Stopping the herb can also shift your INR, this time in the direction of less blood thinning. Tell your clinic so they can monitor you while things settle.
Key takeaways
- Danshen interacts with warfarin through two mechanisms at once: it raises warfarin levels and independently thins the blood.
- Published cases include severe over-anticoagulation and major bleeds, including bleeding into the chest cavity.
- Avoid danshen entirely while on warfarin; do not try to dose-adjust around it.
- If you have already started danshen, contact your anticoagulation clinic for an urgent INR check and do not stop warfarin on your own.
- Treat any sign of bleeding, especially chest pain or sudden breathlessness, as a medical emergency.