Read this booklet to learn:
what warfarin is and why you are taking it
what blood tests you need to use warfarin safely
how other medicines and diet can affect warfarin
what problems (side effects) you should watch for
Information for patients taking warfarin
Please visit the UHN Patient Education website for more health information: www.uhnpatienteducation.ca 2017 University Health Network. All rights reserved. This information is to be used for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis or treatment. Please consult your health care provider for advice about a specific medical condition. A single copy of these materials may be reprinted for non-commercial personal use only.
Author: Joyce Chan, Pharmacist; revised by Amita Woods and Sandra NgRevised: 06/2017Form: D-5600
What is warfarin?Warfarin is an anticoagulant. An anticoagulant is a medicine to help prevent blood clots from forming or to prevent blood clots from getting bigger. Warfarin is also known as Coumadin or other names such as Mylan-Warfarin, Apo-Warfarin, Taro-Warfarin and Teva-Warfarin.
An anticoagulant is sometimes called a blood thinner, but this doesnt mean it thins your blood. Warfarin makes your blood less likely to form clots that are not normal.
Warfarin pills come in different doses (amount of medicine in each pill). Each dose is a different colour pill. Make sure you know what your warfarin pill looks like and what your current dose is.
Why am I taking warfarin?Usually, your blood clots only after an injury, like a cut. You are taking warfarin because an abnormal blood clot has formed in your body or you have a higher chance of forming blood clots. You are taking warfarin because you have:
atrial fibrillation (irregular heartbeat)
tissue heart valve replacement
artificial heart valve replacement
heart valve repair
deep venous thrombosis (clot in your leg)
pulmonary embolism (clot in your lung)
Taking warfarin regularly helps stop an abnormal clot from getting bigger or helps prevent blood clots from forming. This decreases your chance of having a heart attack or stroke.
How long will I have to take warfarin?Many people must take warfarin for the rest of their lives. Others only need it for a short time. Dont stop taking warfarin without talking with your doctor or other health care provider.
What does warfarin do in my body?Warfarin decreases the amount of clotting factors in your blood. This means that warfarin makes your blood less likely to form clots that are not normal.
What blood tests do I need while I am taking warfarin?There is a blood test that will help your health care provider make sure you are taking the right dose (amount). The blood test is called the International Normalized Ratio (INR). The INR shows whether the amount of warfarin you are taking is too little or too much.
In your case, your INR result should be between:
______ to ______
If your INR is not within this range, your warfarin dose may need to be changed.
Taking too much warfarin increases your risk of serious bleeding. Taking too little warfarin increases your risk of an abnormal blood clot causing a heart attack or stroke.
How often do I need to have the INR blood test?You will have an INR blood test almost every day during your hospital stay. Before you go home, we will tell you how much warfarin to take until you meet with the health care provider (such as your family doctor) who will prescribe or monitor your warfarin over time.
When you first go home on warfarin, you may need a blood test every 3 or 4 days. To help you remember when you next blood test is, mark it in a calendar. You can also use the calendar to record your INR results. Once your health care provider knows the right dose for you to take, you wont have to have blood tests as often.
Once you are taking the same dose for several weeks, you will be scheduled for regular INR tests. This may be once every month or more, depending on your situation.
Who will review my INR results and call me about what to do next?The health care provider who will prescribe or monitor your warfarin will contact you. They will let you know if there should be any changes to the dose of warfarin you are taking. They will also tell you when you need to go for your next blood test.
Can I take other medicines while I am on warfarin?Many medicines can change how warfarin works in your body. This includes:
over-the-counter medicines you can buy at a pharmacy without a prescriptionfor example, acetaminophen (Tylenol), ibuprofen (Advil) or naproxen (Aleve)
Always tell your health care provider about changes to any medicines including vitamins, supplements, herbals, or over-the-counter medicines. Your health care provider may need to change the dose of warfarin you take or have you do more INR tests.
Tell all your health care providers, including your dentist, you are taking warfarin. This will help them reduce your risk of bleeding.
What other things will affect the way warfarin works in my body?Things such as illness (for example, the flu or a cold), diet or alcohol can affect the way warfarin works in your body. Always tell your health care provider about any changes to your health, activities and habits.
Forgetting to take your warfarin, especially a day or two before your scheduled INR test can also affect the results.
How should I take warfarin ?You can take warfarin with or without food.
Take warfarin once a day. Try taking warfarin at the same time each day.
In the hospital, we give you warfarin at 6:00 p.m. each day. Its better to take it late in the day, since you usually have your blood tests in the morning. This way, any changes to your dose can start that day.
What if I miss a dose?If you miss a dose, take it as soon as you remember, if you remember on the same day. If you remember the next day, take your regular dose. Dont double the amount or take extra. Tell your health care provider the next time you contact them.
If you forget to take it 2 times in a row, call your health care provider right away. Whenever you are not sure what to do, contact your health care provider.
Do I need to avoid foods with vitamin K?No. You dont need to stop eating foods with vitamin K because many of these foods are healthy for you. Examples of foods high in vitamin K include leafy greens like:
spinach kale broccoli brussel sprouts asparagus
Cooking these foods doesnt change the amount of vitamin K in them.The amount of vitamin K in your body will affect your INR and warfarin dose. Changes in vitamin K levels can affect your INR, so try to eat about the same amount each day.
Talk to your health care provider before you make any major changes to your diet.
Is it safe to drink alcohol?Dont drink more than 1 alcoholic drink a day while you are on warfarin.
1 drink is equal to:
Drinking more than this amount can raise your INR and increase your chance of bleeding.
12 ounces (341 millilitres)
5 ounces (142 millilitres)
1 ounces (43 millilitres)
What problems should I watch for while taking warfarin?
Tell your doctor right away if you have:
bloody or black bowel movements
blood in your urine (pee)
any unusual bleeding or bleeding that doesnt stop, such as:
nose bleedscoughing up or vomiting bloodlots of bleeding when you brush your teethlots of bleeding from small cutsheavy menstrual bleeding
bruising or swelling for no reason
severe headaches that last a long time
swelling and pain in your abdomen (stomach area)
Tell your doctor right away if you have:
Severe back pain that lasts a long time without any reason
Chills and a fever more than 38 C (100 F) for more than 1 to 2 days
Swelling or redness in your feet and lower legs for more than 1 to 2 days, especially if its painful
Your eyes or skin become yellow
If you have any of these problems, you may need medical help right away and your dose of warfarin may change.
What else do I need to know?
Dont take warfarin if you are pregnant or planning to become pregnant.
Tell your doctor about any falls or injuries before taking warfarin and while you are taking warfarin.
Always check with your doctor or pharmacist before starting or making any changes to your medicines, vitamins or supplements.
This brochure is for your information only. It shouldnt replace talking with your pharmacist. Please talk to your pharmacist or other health care professional if you have any questions about this medicine.