High-Alert Medications

Warfarin (coumadin)

Safety Sheet

Warfarin (coumadin)

Extra care is needed because warfarin is a high-alert medicine.

High-alert medicines have been proven to be safe and effective. But these medicines can cause serious injury if a mistake happens while taking them. This means that it is very important for you to know about this medicine and take it exactly as directed.

Top 10 List of Safety Tips for Warfarin

When taking warfarin (blood thinner)

  • Take exactly as directed. Take your medicine at the same time each day. Do not take extra doses or skip any doses.

When the doctor changes your dose

  • Keep a record of telephone calls. When your doctor, nurse, or pharmacist calls to change your dose: write down the dose and any other instructions; read the dose and instructions back to him or her to make sure you understand them; and date the instructions so they won't be mixed up with older instructions.
  • Know your dose. Always tell your doctor the strength of warfarin tablets that you have on hand. Then ask him or her how much warfarin to take, and how many tablets in that strength to take to equal the dose. If you are running low on tablets, ask for a new prescription.
  • Keep instructions nearby. Keep the dated instructions near the medicine, and read them every time before taking your warfarin.
  • Restart your medicine. If your doctor told you to stop taking warfarin until your next blood test, call him or her if you don’t hear anything within 24 hours of the test to find out your new dose or when to restart your prior dose.

When the doctor changes your dose

  • Keep to your regular habits. Keep your eating habits and exercise regular. Know the foods high in vitamin K to avoid or eat consistently. Tell your doctor if there has been a recent change in your level of exercise, diet, or how often you smoke.
  • Take precautions. Because serious bleeding can occur, take precautions. Use an electric razor, avoid sharp objects, and keep away from fall risks (climbing ladders, for example).
  • Get regular blood tests. Keep all appointments for regular blood tests (called INR). Call your doctor for your test results if you are not contacted within 24 hours of the test.

When you should call your doctor

  • Signs of bleeding or clot. Call your doctor immediately if you experience any signs of bleeding or clot formation, which are listed on the other side of this paper.
  • New medicines. Do not start or stop any prescription or nonprescription medicines, herbals, or vitamins without telling your doctor. Common nonprescription medicines to avoid can be found in the Fast Facts table.

Signs of bleeding

  • Unusual pain, swelling, discomfort (may also be a sign of a clot)
  • Unusual or easy bruising
  • Pink or brown urine
  • Prolonged bleeding of gums or cuts
  • Persistent, frequent nosebleeds that don't stop within 7 minutes
  • Unusually heavy/long menstrual flow
  • Coughing up blood
  • Vomit that is bloody or looks like coffee grounds
  • Severe dizziness, weakness, headache, fainting, unusual or persistent tiredness
  • Bloody or black stools
  • Pain in joints or back

Signs of a clot

  • In the lung: chest pain, fast heart rate, coughing, shortness of breath, fever
  • In the arm or leg: sudden leg, arm, or back pain, swelling, redness, warmth, tenderness
  • In the brain: headache, vision changes, seizure, slurred speech, weakness on one side of body, dizziness
  • In the heart: chest pain, shortness of breath, sweating, nausea and vomiting
  • In the abdomen: abdominal pain, vomiting, diarrhea

Some foods high in vitamin K


  • Cranberries/cranberry juice

Avoid or eat in consistent amounts

  • Beef or pork liver
  • Green tea
  • Broccoli and Brussels sprouts
  • Chickpeas
  • Green leafy vegetables, such as spinach, kale, turnip greens, Swiss chard, cabbage
  • Parsley, basil, thyme
  • Many cooking oils
  • Click here for more foods high in vitamin K.

 Topics Fast Facts
Generic name
  • warfarin (pronounced WAR far in) (generic available)
Common brand names
  • Coumadin and Jantoven
Common uses
  • Prevent and treat blood clots in certain conditions that increase the risk of clots: surgery, heart attack, heart rhythm problem, heart valve replacement, immobility after an accident
  • Prevent transient ischemic attacks (mini strokes, brief episodes of low oxygen to the brain)
Usual dose
  • Up to 10 mg daily for adult patients; your dose may be based on a lab test that shows how sensitive you are to the medicine
  • Doses are periodically adjusted based on INR blood test results
What to do if you miss a dose
  • If it is still the same day, take the dose as soon as you remember it
  • If it is the next day, skip the missed dose and take your normal dose
  • Do not double the dose to catch up
  • Contact your doctor if you miss two or more doses in a row
Special instructions and precautions
  • Take exactly as prescribed, the same time each day
  • Avoid alcohol, keep eating habits and exercise regular
  • You will have a tendency to bleed easily, so use a soft toothbrush, waxed dental floss, electric razor; avoid sharp objects and fall risks, such as climbing a ladder
  • Do not start or stop any medicine, including nonprescription medicines, herbals, and vitamins, without letting your doctor or pharmacist know
Safety during pregnancy/breastfeeding
  • Do not take when pregnant, may cause fetal bleeding or abnormalities
  • May take while breastfeeding, but let the infant's doctor know for proper monitoring
Tell your doctor if you have:
  • Diseases: bleeding disorders, kidney disease, liver disease, thyroid disease, severe high blood pressure, diabetes
  • Conditions: surgery, history of falls or if you are at risk for falls, open wound
Storage and disposal
  • Store at room temperature, protect from light and moisture (do not store in bathroom)
  • Dispose of tablets securely in the trash; do not flush down the toilet
Side effects to report to your doctor immediately
  • Signs of bleeding or clot (see top of page), skin irritation, painful red-purple patches on skin (toe, breast, abdomen), unusual fever, unhealed wounds, yellowing eyes or skin
Other conditions to report to your doctor
  • Accidents or falls (even if you feel fine), new or stopped medicines (including antibiotics, nonprescription drugs, herbals, vitamins), changes in smoking/eating habits, infection
Nonprescription medicines/herbals/vitamins that should not be taken with warfarin
  • Aspirin (unless prescribed by your doctor), nonsteroidal anti-inflammatory drugs (ibuprofen [Advil, Motrin], naproxen [Aleve]), most herbals (particularly cranberry, fenugreek, garlic, ginkgo biloba, glucosamine, American ginseng, ginger, goldenseal, coenzyme Q10, St. John's wort, alfalfa, anise, bilberry), cimetidine (Tagamet), vitamins A or E
Prescription medicines that should not be taken with warfarin
  • Check with your doctor, as many prescription medicines interact with warfarin
  • Tell your doctor and pharmacist about all the medicines you take
Special tests your doctor may prescribe
  • You must have blood tests (called INR) checked regularly
  • Your doctor will determine the right INR level (usually between 2 and 3.5) for you

This information does not replace the need to follow your doctor's instructions and read the drug information leaflet provided with your prescription.

This project was supported by grant number R18HS017910 from the Agency for Healthcare Research and Quality. The content is solely the responsibility of the authors and does not represent the official views of the Agency for Healthcare Research and Quality.