When you take fish oil, a dietary supplement rich in omega-3 fatty acids, commonly used to support heart and brain health. Also known as omega-3 supplements, it’s one of the most popular natural products sold worldwide. But if you’re on blood thinners or have a bleeding disorder, fish oil can increase your risk of uncontrolled bleeding—even at standard doses.
That’s because omega-3 fatty acids, the active compounds in fish oil, reduce blood clotting by making platelets less sticky. This is why doctors sometimes recommend it for heart health—it helps prevent clots that cause heart attacks and strokes. But when combined with warfarin, a common blood thinner prescribed to manage abnormal clotting. Also known as Coumadin, it’s a drug that requires careful monitoring through regular INR tests, fish oil can push your blood too far in the thinning direction. Studies show that high-dose fish oil (over 3 grams daily) can raise INR levels, increasing the chance of nosebleeds, bruising, or worse—internal bleeding.
If you’re taking fish oil and also use aspirin, clopidogrel, or any other antiplatelet drug, your bleeding risk doubles. People with liver disease, hemophilia, or recent surgery are especially vulnerable. Even if you’re healthy, taking more than 2 grams of fish oil daily without medical advice isn’t harmless. One patient in a 2022 case report developed a brain hemorrhage after combining 4 grams of fish oil with low-dose aspirin. He had no history of bleeding—until he started the supplement.
Here’s the thing: fish oil isn’t dangerous for everyone. For most people taking 1 gram or less per day, the benefits outweigh the risks. But if you’re on anticoagulants, your doctor should know about every supplement you take—not just prescriptions. Many patients don’t tell their doctors about fish oil because they think it’s "just a natural remedy." But natural doesn’t mean safe when it interacts with medicine.
You don’t need to quit fish oil if you’re on blood thinners—but you do need to be smart. Get your INR checked regularly. Stick to low doses. Avoid combining it with other blood thinners unless your doctor says it’s okay. And if you notice unusual bruising, bleeding gums, or blood in your stool, stop taking it and call your provider right away.
The posts below cover real cases, dosage guidelines, and safer alternatives—so you can make a decision based on facts, not marketing claims.
Fish oil and aspirin both affect blood clotting, but combining them at standard doses doesn't significantly raise bleeding risk. Learn what the science really says and when to be cautious.
