Possible warfarin side effects and signs of a blood clot

What are side effects of warfarin?

Side effects from warfarin are not common, but can happen. The most common side effect is bleeding. To lower your chance of bleeding, your INR should be in the range set for you. If you have any of the side effects listed below, tell your health-care provider right away. You may need to change your dose.

Signs of bleeding or a high INR:

  • Bleeding from cuts that do not stop
  • Nosebleeds that do not stop
  • Gums bleed when you brush your teeth
  • Coughing up blood
  • Vomit (throw-up) that looks like coffee grounds
  • Bruising for unknown reasons
  • Heavy periods or unexpected bleeding from the vagina
  • Bowel movements (poop) that looks black or have blood in them
  • Rust-colored or dark brown urine (pee)
  • Bleeding in the eye
  • Getting a sudden headache, dizziness, or weakness

Call your health-care provider if you get these signs:

  • Fever and chills for more than two days
  • A stomach ache or diarrhea for more than two days
  • Bad stomach aches, stomach pain, or belly swelling
  • Bad headache
  • Skin rash, hives, or itching

Very rare, but serious, side effects are skin necrosis (death of skin tissue) and purple toe syndrome.

What are signs of a blood clot?

You are taking warfarin to help protect you from having a blood clot or prevent you from getting another one. Call your health-care provider if you have:

  • Painful and constant swelling or redness in your feet, lower legs, or arms
  • Bad headache
  • Blurred vision
  • Dizziness
  • Trouble breathing
  • Chest pain
  • Feelings of severe weakness
  • Numbness or tingling of hands, feet, or face
  • Not being able to move
  • Sudden confusion
Last reviewed: 
August 2017

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