Warfarin side effects Get emergency medical help if you have signs of an allergic reaction to warfarin : hives; difficult breathing; swelling of your face, lips, tongue, or throat. Warfarin increases your risk of bleeding, which can be severe or life-threatening. Learn about side effects, warnings, dosage, and more for warfarin oral tablet. Warfarin oral tablet is a prescription medication used to treat and prevent blood clots in the heart, lower body, and. Be careful not to take more than one medication that contains warfarin unless specifically directed by the doctor or health care provider who is monitoring your warfarin treatment. Dangerous Warfarin Side Effects Following is research for the main long term side effects of blood thinners causing bleeding strokes and hardening of the arteries. But the list of unwanted warfarin side effects is growing! Warfarin, a blood thinner that’s been around for decades, can trigger a range of side effects. Common ones include nausea, vomiting, diarrhea and abdominal pain. The most common side effect — bleeding — can be life-threatening. Rare side effects include stroke, gangrene and death. Some side effects of warfarin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome. Common side effects of warfarin include nausea, vomiting, stomach pain, gas, and bloating. Bleeding may also occur with Coumadin. Signs of bleeding include nose bleeds, bleeding gums, unusual or. “Blood thinners” or anticoagulants are the kind of medication used to prevent the blood clots. Warfarin (Lawarin, Waran, Coumadin, Jantoven, Marevan) is one of those drugs, affecting the clotting proteins and preventing blood clots. Warfarin side effects can also include interactions with some foods, prescription medicines and over-the-counter supplements. If your doctor prescribes warfarin for you, make sure you understand all the potential warfarin side effects and interactions it could have. Warfarin treatment can help prevent formation of future blood clots and help reduce the risk of embolism (migration of a thrombus to a spot where it blocks blood supply to a vital organ)..