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Warfarin: Taking Your Medicine Safely

Warfarin: Taking Your Medicine Safely


Warfarin is a medicine that helps prevent blood clots. Coumadin is the common brand name for warfarin. Because it prevents clots, it also helps prevent heart attacks, strokes, and other problems caused by blood clots.

It's important to know how to take warfarin safely.

How do you take warfarin safely?

Warfarin causes you to bleed more quickly when you're injured. So be sure to avoid doing things that increase your chances of bleeding. These are the four main steps you need to take:

  1. Get regular blood tests.
  2. Prevent falls and injuries.
  3. Be careful with other medicines.
  4. Eat a similar amount of vitamin K every day.

1. Get regular blood tests.

Regular blood tests will help your doctor make sure you are taking the right amount of warfarin.

Things like an infection or a small change in your diet can change the way warfarin works. So can other medicines that you are taking. That's why regular testing is so important. The tests tell your doctor whether your dose needs to be changed.

Don't change your dose or stop taking warfarin unless your doctor tells you to.

2. Prevent falls and injuries.

Make these changes in your life to prevent falls:

  • Wear slippers or shoes that have nonskid soles.
  • Use a cane or walker if you need one.
  • Put things within easy reach so that you don't need to reach over your head for them.
  • Keep a cordless phone and a flashlight with new batteries by your bed.

Make these changes in your home to prevent falls:

  • Remove raised doorway thresholds, throw rugs, and clutter.
  • Rearrange furniture and electrical cords to keep them out of walking paths.
  • Keep stairways, porches, and outside walkways well lit. Use night-lights in hallways and bathrooms.
  • Install sturdy handrails on stairways. Install grab handles and nonskid mats inside and outside your shower or tub and near the toilet.
  • Add extra light switches if needed or use remote switches, such as sound-activated switches, on lights by doors and near your bed. Then you will not have to get up quickly to turn on the light or walk across the room in the dark.
  • Repair loose carpet or raised areas in the floor that may cause you to trip.
  • Use shower chairs and bath benches.
  • Use nonskid floor wax. Wipe up spills right away, especially on ceramic tile floors.
  • If you live in an area that gets snow and ice in the winter, have a family member or friend sprinkle salt or sand on slippery steps and sidewalks.

Make these changes to prevent injuries:

  • Enjoy activities that have a lower risk of injury, like swimming and walking. Try to avoid activities or sports that put you at risk of injury. But if you take part in activities that put you at risk of falling or injury, be as safe as possible and wear protective equipment like helmets.
  • Be extra careful when you work with sharp tools or power tools, such as saws.
  • Use an electric razor, not a razor blade.
  • Use waxed dental floss and a toothbrush with soft bristles.
  • When you work outside, wear clothing that protects you, such as gloves, shoes, and long sleeves.

3. Be careful with other medicines.

Taking other medicines along with warfarin can cause a bad reaction. For example, some medicines can change the way warfarin works so you bleed too easily. Or warfarin can change the way the other medicine works.

Talk to your doctor before you start or stop taking any prescription medicines, over-the-counter medicines, vitamins, or herbal products. If other doctors prescribe something for you, be sure they know that you take warfarin. Here are some examples of medicines that you need to be careful of:

  • Over-the-counter medicines
  • Vitamins and herbal products
    • Garlic pills
    • Green tea leaves. (Green tea leaves contain vitamin K before they are steeped in water, but a small serving of the hot tea itself does not.)
    • Ginkgo biloba
    • Multivitamins
  • Prescription medicines
    • Many medicines affect warfarin or are affected by warfarin.
    • Make sure your doctor knows everything you are taking.

Follow these safety tips for taking medicines:

  • Take your medicine at the same time each day. Most people take their warfarin in the evening.
  • Don't start or stop taking any medicines, vitamins, or natural remedies unless you first talk to your doctor.
  • If you take several medicines, use a daily medicine planner to keep track of them. It's a list of every medicine and vitamin you take, along with when and how often you take each one.
  • Make sure that every doctor and dentist you see knows that you are taking warfarin.

What to do if you miss a dose of your warfarin

If you miss a dose of warfarin, the best thing to do is call your doctor. He or she can tell you exactly what to do so you don't take too much or too little. That way you'll stay as safe as possible.

But here are some general rules:

  • If you remember it in the same day, take the missed dose. Then go back to your regular schedule.
  • If it is the next day or almost time to take the next dose, do not take the missed dose. Do not double the dose to make up for the missed one. At your next regularly scheduled time, take your normal dose.
  • If you miss your dose for 2 or more days, call your doctor.

4. Eat a similar amount of vitamin K every day.

Most people who take warfarin can eat normally. But make sure that you don't suddenly eat a lot more or a lot less food that is high in vitamin K than you usually do.

Vitamin K helps your blood to clot so wounds don't bleed too much. Warfarin makes blood clots form more slowly. Suddenly changing the amount of vitamin K you eat each day could keep warfarin from working well.

How to get a steady amount of vitamin K

  • Don't suddenly change the amount of vitamin K in your diet. Try to keep the amount you eat about the same from day to day. For example, if you don't regularly eat leafy greens, such as spinach, don't suddenly add them to your diet or eat a lot at once.
  • Learn which foods contain vitamin K.
  • If you are used to eating foods that are high in vitamin K, you don't need to change your diet. What is important is to try to keep the amount about the same from day to day.
  • If you take a multivitamin that contains vitamin K, be sure you take it every day.
  • Check with your doctor before you take any supplements or herbal products. Some of these may contain vitamin K.
  • Check with your doctor before you make big changes in what you eat, such as starting a diet to lose weight.

Foods with vitamin K

  • You might limit foods that are high in vitamin K to about 1 serving a day. These foods have about 250 to 500 micrograms (mcg) of vitamin K in each serving. They include:
    • Cooked leafy green vegetables. Examples are kale, spinach, turnip greens, collard greens, Swiss chard, and mustard greens. One serving is ½ cup.
  • You might limit foods that are medium-high in vitamin K to about 3 servings a day. These foods have about 50 to 150 mcg of vitamin K in each serving. These include:
    • Cooked brussels sprouts, broccoli, cabbage, and asparagus. One serving is ½ cup.
    • Raw leafy green vegetables. Examples are spinach, green leaf lettuce, romaine lettuce, and endive. One serving is 1 cup.

More safety tips

Follow these general rules when you take warfarin:

  • Wear a medical alert ID . These are bracelets, pendants, or charms that let others know you take warfarin. Ask your pharmacist for information about ordering one. Medical alert jewelry is also easy to find on the Internet.
  • Don't smoke. Smoking affects how the body uses medicine, and it increases the blood's clotting effects.
  • Limit alcohol. Alcohol can change how warfarin works. Limit alcohol to 2 drinks a day if you are a man, or 1 drink a day if you are a woman.
  • Tell your doctor if you are not able to eat for several days or if you have an upset stomach, diarrhea, or fever.
  • Before a surgery or procedure, tell your doctors that you take warfarin. Your doctor will tell you if you should stop taking it before your surgery. Make sure that you understand exactly what your doctor wants you to do. Your doctor will tell you when it is safe to start taking warfarin again.

Advice for women

If you are pregnant, do not take warfarin. Warfarin can cause miscarriage or birth defects. If you are taking warfarin, talk to your doctor about how you can prevent pregnancy.

If you think you might be pregnant, call your doctor. If you are pregnant, you will take heparin during your pregnancy.

If you plan on getting pregnant, talk with your doctor. You and your doctor will decide which medicine you will take—warfarin or heparin—while trying to get pregnant.

Know the signs of bleeding

Call 911 or other emergency services right away if you have:

  • A sudden, severe headache that is different from past headaches. (It may be a sign of bleeding in the brain.)

Call your doctor now or seek immediate medical care if you have:

  • Any other abnormal bleeding, such as:
    • Coughing up blood.
    • Vomiting blood or what looks like coffee grounds.
    • Stools that are black and look like tar or have streaks of blood.
    • A nosebleed that doesn't stop quickly.
    • Blood in your urine.
    • Vaginal bleeding that is different (heavier, more frequent, at a different time of the month) than what you are used to.
    • New bruises or blood spots under your skin without a known cause.

If you are injured, apply pressure to stop bleeding. Realize that it will take longer than you are used to for the bleeding to stop. If you can't get the bleeding to stop, call your doctor.


Current as of: September 7, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine

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