Ashwagandha can increase bleeding risk. One of its active compounds, withaferin A, has documented anticoagulant and antiplatelet effects, meaning it interferes with your body’s ability to form blood clots. The University of Iowa Health Care explicitly lists ashwagandha among supplements that “may put you at a higher risk of bleeding.” For most healthy people taking standard doses, this effect is unlikely to cause noticeable problems, but it becomes significant if you’re on blood-thinning medications, have a bleeding disorder, or are preparing for surgery.
How Ashwagandha Affects Blood Clotting
The bleeding risk comes from withaferin A, one of the key bioactive compounds in the ashwagandha plant. Lab research published in the journal Thrombosis Research found that withaferin A works through several overlapping mechanisms. It slows down fibrin polymerization, which is the process your body uses to build the mesh-like structure of a blood clot. It also inhibits platelet aggregation, meaning your platelets are less likely to clump together at a wound site. And it interferes with thrombin, the enzyme that sits at the center of the clotting process and triggers much of the cascade that stops bleeding.
In animal models, withaferin A prolonged both in vivo and ex vivo bleeding time. It also shifted the balance between two opposing signals in blood vessel cells: it reduced the molecule that blocks clot breakdown (PAI-1) while leaving the molecule that promotes clot breakdown (t-PA) relatively intact. The net result is that existing clots dissolve more easily and new clots form more slowly. These are the same basic mechanisms that prescription blood thinners target, though ashwagandha’s effects are less potent and less predictable than a controlled pharmaceutical dose.
Gastrointestinal Side Effects
Ashwagandha can also irritate the digestive tract, especially at higher doses. Reported symptoms include nausea, vomiting, diarrhea, and abdominal cramps. Researchers attribute this to direct irritation of the intestinal lining. While this is different from internal bleeding, mucosal irritation in the stomach or intestines can theoretically worsen existing conditions like gastritis or ulcers, where the lining is already compromised.
If you notice dark or tarry stools, vomiting that looks like coffee grounds, or unusual stomach pain while taking ashwagandha, those are signs of possible gastrointestinal bleeding that warrant medical attention. These symptoms are rare with ashwagandha alone but become more plausible if you’re also taking NSAIDs like ibuprofen or aspirin, which carry their own risks to the stomach lining.
Who Faces the Highest Risk
The bleeding concern matters most for specific groups:
- People on anticoagulant or antiplatelet medications. If you take warfarin, heparin, aspirin, or similar drugs, ashwagandha’s clot-inhibiting effects can stack on top of your medication. This combination can push bleeding risk higher than either one alone, and because ashwagandha’s potency varies between products, the added risk is hard to predict.
- People with bleeding disorders. Conditions like hemophilia or von Willebrand disease already impair clot formation. Adding a supplement that further slows clotting can make spontaneous bleeding episodes more frequent or harder to control.
- People approaching surgery. Any procedure that involves cutting tissue relies on your body’s clotting system to prevent excessive blood loss. Even minor dental work can become complicated if clotting is impaired.
For healthy adults not in any of these categories, the anticoagulant effect of ashwagandha at typical supplement doses (300 to 600 mg of root extract daily) is unlikely to cause spontaneous bleeding. The risk is real but contextual. It depends heavily on what else is in your system and whether your clotting ability is already reduced for another reason.
Stopping Ashwagandha Before Surgery
Both the American Society of Anesthesiologists and the American Association of Nurse Anesthetists recommend stopping herbal medications one to two weeks before elective surgical procedures. This guidance applies broadly to herbs that affect clotting, and ashwagandha falls squarely in that category. The timeline gives your body enough time to clear the active compounds and restore normal clotting function.
If you’re scheduled for any procedure, including dental surgery, mention your ashwagandha use to your surgical team even if they don’t ask. Many preoperative questionnaires focus on prescription medications and miss supplements entirely. Withaferin A’s effects on clotting are well-documented enough that your anesthesiologist will want to account for it.
Other Supplements With Similar Effects
Ashwagandha is far from the only supplement that increases bleeding risk. Turmeric, ginkgo biloba, fish oil, garlic supplements, ginger, feverfew, ginseng, and vitamin E all have anticoagulant or antiplatelet properties. If you’re combining ashwagandha with any of these, the effects can compound. A person taking fish oil, turmeric, and ashwagandha together is layering three different sources of clotting interference, which creates a cumulative risk that none of those supplements would carry individually.
The practical takeaway: ashwagandha does have real, measurable effects on blood clotting. For most people, those effects stay below the threshold of clinical concern. But if you have any reason to worry about bleeding, whether from medications, a known disorder, or an upcoming procedure, it’s a supplement that deserves careful consideration rather than casual use.