Possible warfarin side effects and signs of a blood clot

What are side effects of warfarin?

Side effects are not common but can happen. The most common are bruising or minor bleeding. Expect to bruise easier while on warfarin. To lower your chance of bleeding, your INR should be in the range set for you. Tell your provider right away if you have any side effects listed below. You may need to change your dose.

Signs of bleeding or a high INR are:

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

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 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

Call your provider if you have:

  • Fever and chills for more than 2 days
  • A stomachache or diarrhea for more than 2 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.

Last reviewed: 
December 2021

Interested in using our health content?