Warfarin Side Effects

For the Consumer

Applies to warfarin: oral tablet

As well as its needed effects, warfarin may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking warfarin, check with your doctor immediately:

Less common:

• Abdominal or stomach pain with cramping
• bleeding gums
• blood in the urine
• bloody stools
• blurred vision
• burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
• chest pain or discomfort
• confusion
• coughing up blood
• difficulty with breathing or swallowing
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• excessive bruising
• headache
• increased menstrual flow or vaginal bleeding
• nosebleeds
• paralysis
• peeling of the skin
• prolonged bleeding from cuts
• red or black, tarry stools
• red or dark brown urine
• sweating
• unexplained swelling
• unusual tiredness or weakness

Rare

• Arm, back, or jaw pain
• blue-green to black skin discoloration
• blue or purple toes
• change in consciousness
• chest tightness or heaviness
• chills
• clay-colored stools
• diarrhea
• dizziness
• fainting or loss of consciousness
• fast or irregular breathing
• fast or irregular heartbeat
• fever
• itching or skin rash
• light-colored stools
• loss of appetite
• nausea and vomiting
• pain in the toes
• pain, redness, or sloughing of the skin
• pale skin
• purplish red, net-like, blotchy spots on the skin
• skin blisters
• small red or purple spots on the skin
• stomach pain
• swelling of the eyes or eyelids
• tightness in the chest
• troubled breathing with exertion
• unpleasant breath odor
• unusual bleeding or bruising
• upper right abdominal or stomach pain
• vomiting of blood
• yellow eyes and skin

Minor Side Effects

Some warfarin side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:

• Joint pain
• muscle pain

Rare

• Bloated
• change in taste, or bad, unusual, or unpleasant (after) taste
• cold intolerance
• excess air or gas in the stomach or intestines
• full feeling
• general feeling of discomfort or illness
• hair loss or thinning of the hair
• hives or welts
• lack or loss of strength
• pain
• passing gas
• red, sore, or itching skin
• sores, welting, or blisters
• unusual drowsiness, dullness, or feeling of sluggishness

For Healthcare Professionals

Applies to warfarin: compounding powder, intravenous powder for injection, oral tablet

General

The most common adverse reactions were fatal and nonfatal hemorrhage from any tissue or organ.^[Ref]

Cardiovascular

Frequency not reported: Hemorrhage, purple toes syndrome, infarction, systemic cholesterol microembolization, vasculitis, systemic atheroemboli^[Ref]

Nervous system

Frequency not reported: Cerebral hemorrhage, cerebral subdural hematoma, lethargy, headache, dizziness, taste perversion, paresthesia^[Ref]

Gastrointestinal

Frequency not reported: Gastrointestinal hemorrhage, rectal hemorrhage, hematemesis, pancreatitis, diarrhea, nausea, vomiting, melena, abdominal pain, cramping, flatulence, bloating^[Ref]

Dermatologic

Frequency not reported: Rash, alopecia, purpura, erythematous swollen skin patches, ecchymosis, skin necrosis, dermatitis, bullous eruptions, urticaria, pruritus^[Ref]

Musculoskeletal

Frequency not reported: Tissue necrosis, chills^[Ref]

Metabolic

Frequency not reported: Calciphylaxis, edema^[Ref]

Respiratory

Frequency not reported: Hemothorax, epistaxis, tracheal or tracheobronchial calcification^[Ref]

Genitourinary

Frequency not reported: Hematuria^[Ref]

Hematologic

Frequency not reported: Unexplained decrease in hematocrit, hemoglobin decreased^[Ref]

Hepatic

Frequency not reported: Jaundice, hepatic dysfunction, hepatitis, cholestatic hepatic injury, liver enzymes elevated^[Ref]

Immunologic

Frequency not reported: Hypersensitivity, allergic reactions, anaphylactic reactions^[Ref]

Other

Frequency not reported: Fever, fatigue, malaise, asthenia, pain, cold intolerance, feeling cold^[Ref]

It is possible that some side effects of warfarin may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.