Does warfarin make you tired


Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 9/5/2018

Coumadin (warfarin) is a blood anticoagulant that inhibits the function of Vitamin K dependent coagulation used to inhibit the coagulation of blood to reduce or prevent the chance of developing heart attacks (myocardial infarctions), strokes, and venous and other blood clots (deep venous thromboses, pulmonary emboli and thrombi produced with atrial fibrillation). Coumadin is also used to treat these conditions if they develop. Coumadin is available as a generic. Common side effects of Coumadin include

  • easy bruising and bleeding,
  • nausea,
  • vomiting,
  • stomach pain,
  • bloating,
  • gas, or
  • altered sense of taste.

Coumadin has a wide range of tablets: 2, 2.5, 3, 4, 5, 6, 7.5 and 10 mg tablets are available. An injectable form of the drug (5 mg) is also available. The dose of Coumadin is determined in each individual by administering a trial dose and ten measuring the patient’s INR (International Normalized Ratio), a lab test that is standardized by the WHO (world Health Organization) and recognized worldwide. Therapeutic ranges for this test are between 2.0 to 3.0 when a patient is taking Coumadin. INR levels below 2 may allow easier blood clotting to occur while levels above 3 may cause excessive tendency for the patient to bleed. Coumadin may interact with other medications to prevent blood clots, antibiotics, antifungals, sulfa drugs, medicines to treat tuberculosis, antidepressants, herbal (botanical) products (including coenzyme Q10, cranberry, echinacea, garlic, ginkgo biloba, ginseng, goldenseal, or St. John’s wort), secobarbital, barbiturates, seizure medications, and other drugs. Tell your doctor all medications and supplements you use. Pregnant women should not be given Coumadin; lactating women may need to be closely monitored and their breastfed infants should have their INR checked, according to some investigators. Although Coumadin has been used in pediatric patients to prevent clot formations, children under 18 have not been well studied with this drug and some investigators suggest achieving stable INR levels seems more difficult in the pediatric population.

Our Coumadin Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Warfarin (brand names Coumadin and Jantoven) is a prescription medication used to prevent harmful blood clots from forming or growing larger. Beneficial blood clots prevent or stop bleeding, but harmful blood clots can cause a heart attack, stroke, deep vein thrombosis or pulmonary embolism. Because warfarin interferes with the formation of blood clots, it is called an anticoagulant (PDF). Many people refer to anticoagulants as *blood thinners; however, warfarin does not thin the blood but instead causes the blood to take longer to form a clot.

How Does Warfarin Work?

The formation of a clot in the body is a complex process that involves multiple substances called clotting factors. Warfarin decreases the body’s ability to form blood clots by blocking the formation of vitamin K–dependent clotting factors. Vitamin K is needed to make clotting factors and prevent bleeding. Therefore, by giving a medication that blocks the clotting factors, your body can stop harmful clots from forming and prevent clots from getting larger.

Monitoring and Dosing Tips

The goal of warfarin therapy is to decrease the clotting tendency of blood, not to prevent clotting completely. Therefore, the effect of warfarin must be monitored carefully with blood testing. On the basis of the results of the blood test, your daily dose of warfarin will be adjusted to keep your clotting time within a target range. The blood test used to measure the time it takes for blood to clot is referred to as a prothrombin time test, or protime (PT). The PT is reported as the International Normalized Ratio (INR).

The INR is a standardized way of expressing the PT value. The INR ensures that PT results obtained by different laboratories can be compared. It is important to monitor the INR (at least once a month and sometimes as often as twice weekly) to make sure that the level of warfarin remains in the effective range. If the INR is too low, blood clots will not be prevented, but if the INR is too high, there is an increased risk of bleeding. This is why those who take warfarin must have their blood tested so frequently.

Unlike most medications that are administered as a fixed dose, warfarin dosing is adjusted according to the INR blood test results; therefore, the dose usually changes over time. Coumadin/ warfarin pills come in different colors, and each color corresponds to a different dose (see graphic below).

Difference Between Brand-Name and Generic Medications

Generic drugs are supposed to have the same dosage, therapeutic effects, route of administration, side effects, and strength as the original drug. The U.S. Food and Drug Administration requires that all generic drugs be as safe and effective as brand-name drugs.

Generic drugs are often less expensive than their brand-name counterparts, because the generic manufacturers have not incurred the expenses of developing and marketing a new drug. In the United States, trademark laws do not allow generic drugs to look exactly like the brand-name drug; however, the generic drug must have the same active ingredients. In the case of Coumadin (a brand-name product) and warfarin (a generic product), the manufacturers attempted to keep the colors consistent with the strength of the pills. The goal is to allow the patient to identify the color-coded dose and prevent mix-ups or errors. Therefore, if the color or dose of the dispensed tablet appears different from the pill taken previously, the patient should immediately notify the dispensing pharmacist or healthcare provider.

In 2006, the Food and Drug Administration issued a public health advisory to healthcare professionals and consumers that U.S. prescriptions filled abroad may give patients the wrong active ingredient for treating their health condition. Some FDA–approved products have the same brand names as drug products marketed outside the United States but contain completely different active ingredients. Therefore, patients who fill U.S. prescriptions abroad, either when traveling or online, need to maintain caution and vigilance. We advise U.S. residents against purchasing drugs at foreign Internet pharmacies. Foreign drugs may use identical or potentially confusing brand names for products with active ingredients that differ from U.S. drugs. Warfarin has many foreign brand names (Table 1). Patients who do fill prescriptions abroad should ensure the accuracy and quality of the medication dispensed.

Warfarin must be taken exactly as prescribed.

Never increase or decrease your dose unless instructed to do so by your healthcare provider. If a dose is missed or forgotten, call your healthcare provider for advice.

Foreign Brand Names for Warfarin

Country Foreign Brand Name for Warfarin
Australia Warfarin, Marevan
Canada Apo-Warfarin
Indonesia Simarc-2
Portugal Varfine
Spain Aldocumar
Thailand Befarin, Maforan, Fargem
Turkey Orfarin
Venezuela Anasmol, Cumar

Side Effects

The major complications associated with warfarin are clotting due to underdosing or bleeding due to excessive anticoagulation. The most serious bleeding is gastrointestinal or intracerebral. Excessive bleeding can occur in any area of the body, and patients taking warfarin should report any falls or accidents, as well as signs or symptoms of bleeding or unusual bruising, to their healthcare provider.

Signs of unusual bleeding include:

  • bleeding from the gums,
  • blood in the urine,
  • bloody or dark stool,
  • a nosebleed, or
  • vomiting blood.

An unusual headache or a headache that is more severe than usual may signal intracerebral bleeding.

When to Call Your Healthcare Provider

If you experience the following signs of bleeding, you should call 911 or your healthcare provider immediately:

  • Severe headache, confusion, weakness or numbness
  • Coughing up large amounts of bright red blood
  • Vomiting blood
  • Bleeding that will not stop
  • Bright red blood in stool
  • Fall or injury to the head
  • Headache that is severe or unusual

Some simple changes to decrease the risk of bleeding while taking warfarin include the following:

  • Use a soft-bristle toothbrush
  • Floss with waxed floss rather than unwaxed floss
  • Shave with an electric razor rather than a blade
  • Take care when using sharp objects, such as knives and scissors
  • Avoid activities that have a risk of falling or injury (e.g., contact sports)

Warfarin and Lifestyle

Changes in daily living can affect the INR. It is important to know common do’s and don’ts for warfarin therapy.


Warfarin is not recommended during pregnancy. A woman who becomes pregnant or plans to become pregnant while undergoing warfarin therapy should notify her healthcare provider immediately.

Surgery/Dental and Other Medical Procedures

It is important to tell all your healthcare providers that you are taking warfarin. If you are having surgery, dental work, or other medical procedures, you may need to stop taking warfarin.


Check with your healthcare provider if you expect to travel. While traveling, it is important to carry your medication with you at all times. Do not put medication into checked baggage.

Common Do’s and Don’ts

What to Do What Not to Do
Do watch for signs and symptoms of bleeding. Never double a dose because you missed a dose.
Do tell your healthcare provider when you get sick or hurt. Don’t start new medications, herbals, or supplements without talking to your healthcare provider.
Do take warfarin exactly as prescribed. Don’t make changes to your warfarin dose without talking to your healthcare provider.
Do tell anyone giving you medical or dental care that you are taking warfarin.
Do keep appointments for blood tests.

Warfarin Interacts With Other Medications

Patients who take warfarin should consult with their healthcare provider before taking any new medication, including over-the-counter (nonprescription) drugs, herbal medicines, vitamins or any other products. Many medications can alter the effectiveness of warfarin, resulting in an INR that is either too high or too low. Some of the most common over-the-counter pain relievers, such as: ibuprofen (brand name Advil) and naproxen (brand name Aleve), enhance the anticoagulant effects of warfarin and increase the likelihood of harmful bleeding.

Warfarin Interacts With Alcohol and With Certain Foods

  • Alcohol – Alcohol intake can affect how the body metabolizes warfarin. Patients undergoing warfarin therapy should avoid drinking alcohol on a daily basis. Alcohol should be limited to no more than 1 to 2 servings of alcohol occasionally. This means an average of one to two drinks per day for men and one drink per day for women. (A drink is one 12 oz. beer, 4 oz. of wine, 1/5 oz. of 80-proof spirits, or 1 oz. of 100-proof spirits). The antiplatelet effect of alcohol increases the risk of major bleeding, even if the INR remains within the target range.
  • Foods – Some foods can interfere with the effectiveness of warfarin. The most important point to remember is to eat what you normally eat and not to make any major changes in your diet without contacting your healthcare provider.
  • Vitamin K – Eating an increased amount of foods rich in vitamin K can lower the PT and INR, making warfarin less effective and potentially increasing the risk of blood clots. Patients who take warfarin should aim to eat a relatively similar amount of vitamin K each week. The highest amount of vitamin K is found in green and leafy vegetables such as broccoli, lettuce, and spinach. It is not necessary to avoid these foods; however, it is important to try to keep the amount of vitamin K you eat consistent. Download our quick reference guide to foods that are high and low in Vitamin K. (PDF)

Wear Medical Identification

Those who require long-term warfarin should wear a medical alert bracelet, necklace, or similar alert tag at all times. If an accident occurs and the person is too ill to communicate, a medical alert tag will help responders provide appropriate care. The alert should include a list of major medical conditions and the reason warfarin is needed, as well as the name and phone number of an emergency contact.

Where to Get More Information

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no 2 patients are exactly alike, and recommendations can vary from 1 person to another, it is important to seek guidance from a provider who is familiar with your individual condition.

Ask Dr. Gourmet

Does Coumadin (warfarin) cause fatigue?

My mother is on Coumadin. She is also on Vicodin for pain. She is chronically tired all the time! Is Coumadin a contributing factor for this tiredness? I know that the Vicodin is. Can you help me know what foods she could eat to boost her energy?

Dr. Gourmet Says…

Certainly the Vicodin can be a major contributing factor to your mother’s fatigue. Using narcotics in the elderly for pain control can be a challenge.

Fatigue is not a common complaint of those using Coumadin® (warfarin), but I have learned in my practice that patients will react to medications in different ways – so it is possible that your mother’s tiredness is related. As a physician I always have to ask if there is some medication that I might be prescribing that could cause issues. There are common medications that some take while taking Coumadin that might be involved. These include beta blockers (atenolol, metoprolol, propranolol, etc.), calcium channel blockers (amlodipine, diltiazem) as well as many anti-depressants.

Oftentimes depression can be the culprit, and fatigue in the elderly always makes me question if this is an issue. Part of the work up for fatigue and depression includes evaluating thyroid function and Vitamin B12 levels. Hemoglobin is key in the work up for fatigue as well. Chat with her about going with her to the next doctor’s appointment. Many times our elderly patients will tell their physicians “everything’s just fine” when it isn’t. I have been told many times by patients, “I just didn’t want to bother you with my problems – you need to take your time with someone who is really sick.” (Except, of course, it’s your mother who we want to take care of.)

There is a great deal of controversy about whether foods can boost energy or not. Certainly there are thousands of websites purporting that particular foods and diets can provide everything from energy to longevity to boosting the immune system. While much of the research that has been done is encouraging regarding the effect of diet on long term health, most are smaller studies and require more research. Likewise, few have shown specific short term benefits for malaise and fatigue.

That said, I do find diet to often be a concern. A major issue in the elderly can be that they will often not cook fresh foods for themselves and sometimes eat less healthy. Skipping meals can be a major problem, as well as relying on more processed foods and not getting fresh, whole foods. The consequence can be fewer calories than they actually need and the quality of those calories can be lacking.

One strategy is to ask her if you can take a look in her cabinets and fridge. Sometimes the food is there but she might not be eating it. Having your mom keep a food diary can be one path to seeing what she is eating and how often.

Lastly, there are many services that will help provide her with ready made meals. Check with your local grocery about whether they are able to help.

Thanks for writing,

Timothy S. Harlan, MD, FACP, CCMS
Dr. Gourmet

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Warfarin (Coumadin®) Anticoagulant Medication


What is warfarin?

Warfarin sodium is an anticoagulant medication. “Anti” means against and “coagulant” means causing blood clotting. Warfarin controls the way that blood clots (thickens into a lump) inside your blood vessels. The brand names of warfarin are Coumadin® and Jantoven®.

What do anticoagulants like warfarin do?

An anticoagulant helps your body control how fast your blood clots, which helps prevent unwanted clots from forming inside your arteries, veins, or heart during certain medical conditions and during long periods of physical inactivity.

If you have a blood clot, an anticoagulant may keep the clot from getting larger. It also may prevent a piece of the clot from breaking off and traveling to your lungs, brain or heart. An anticoagulant also helps prevent new clots from forming.

An anticoagulant does not dissolve the blood clot. With time, however, a clot may dissolve on its own.

How do I take warfarin?

You will take warfarin every day. The dose usually ranges from 1 mg to 10 mg. Your healthcare provider will prescribe a specific dosage strength, however, keep in mind that this dosage may change based on the results of each laboratory test.

Other instructions for taking warfarin include:

  • Take your dose of warfarin as instructed once a day.
  • Take the dose at the same time each day. We recommend 5:00 p.m.
  • Warfarin can be taken before or after eating.
  • If you forget to take your dose and remember within eight hours of the time you were supposed to take your dose, take the dose. If it is past eight hours, wait until the next day and take only the prescribed dose for that day. DO NOT TAKE A DOUBLE DOSE.
  • If you forget to take your warfarin two or more days in a row, call your healthcare provider. The dose may need to be changed. (Never change the dose yourself without calling your provider first.)
  • Consider using a pillbox to help you remember to take your medication or get a calendar and check off every day after you take your dose.
  • Refill your prescription one week before your supply runs out to avoid missing a dose.
  • Continue to take warfarin as long as your provider prescribes it. Never stop taking warfarin on your own without discussing this with your provider.

Tablet appearance

Warfarin is made by several drug manufacturers and is available as a tablet in many different shapes, sizes and colors. Each tablet color represents a different strength, measured in milligrams (mg). All manufacturers follow the same color code for the different strengths of their tablets, however, the size and shape of the tablets may differ from one manufacturer to the next.

Dosage Strength Tablet Color
1 mg pink
2 mg lavender
2.5 mg green
3 mg tan
4 mg blue
5 mg peach
6 mg teal or blue-green
7.5 mg yellow
10 mg white

Each tablet has its strength stamped on one side and is scored (has an indent across the tablet) so it can easily be broken in half if your healthcare provider adjusts your dose. For example: if your provider prescribes a 5-mg tablet and then changes your dose to 2.5 mg (2½ mg), which is half the strength, you should break one of the 5-mg tablets in half and take the half-tablet. If you have any questions about your dose of warfarin, contact your provider.

What blood tests will I need while I am on warfarin?

You will need to have your blood tested to tell how well the medication is working. The blood test, called prothrombin time (PT or protime), is used to calculate your International Normalized Ratio (INR). Your INR helps your healthcare provider determine how well warfarin is working to prevent blood clots and if the dose needs to be adjusted.

Blood tests are done at a laboratory or anticoagulation clinic, in a medical office or at home. Blood tests are typically done from one or more times a week to once a month (if your results have been stable). Follow your provider’s instructions for how often you need to get blood tests and when to adjust your daily warfarin dose.

Other information about your blood tests:

  • Illness, health status, diet or medication changes can affect your INR. Tell your healthcare provider about changes in your health, medications (prescription and over-the-counter) or lifestyle so appropriate dosage adjustments can be made.
  • If you are planning a trip, talk with your provider about using another laboratory for your blood tests while traveling.

Where should I store warfarin?

Store warfarin at room temperature, away from extreme cold, heat, light and moisture. Never store medications in bathroom cabinets because of the moisture found in bathrooms.

Always keep medications out of the reach of children and pets.

What precautions should I take while taking warfarin?

It is important that you follow these precautions when taking warfarin.


It is important to avoid getting pregnant while on warfarin. Use reliable birth control methods to prevent pregnancy if you are a female and have not yet reached menopause.

If you are taking warfarin and planning to become pregnant, talk with your doctor about the possible risks and ways to reduce those risks. Tell your doctor right away if you become pregnant or think you might be pregnant.

Surgery and dental work

Before receiving any treatment, tell all of your doctors and dentists you are taking warfarin. You may need to have a blood test and stop taking warfarin for a few days before having surgery or a dental procedure.

Be sure to contact your healthcare provider who monitors your warfarin at least two weeks before any dental or surgical procedure if possible. Do not stop taking warfarin without talking to your healthcare provider first.


Check with your provider before starting any exercise or sports program. Talk with your provider if you are planning any major diet changes such as a weight-reducing diet, or if you plan to add any nutritional supplements.


Foods and vitamin K. Vitamin K is needed for normal blood clotting. However, large changes in the amount of vitamin K in your diet can change the way warfarin works. If you eat foods high in vitamin K, it’s important to keep your weekly intake of vitamin K-containing foods consistent.

Tell your provider if you are thinking about changing your current eating habits. Tell your provider if you are planning to:

  • Eat more or fewer vegetables.
  • Change to a vegetarian style of eating.
  • Follow a special meal plan to lose or gain weight.

Changing your eating habits may mean that you will be getting more or less Vitamin K in the foods you eat. If you change your eating habits, your provider may want to check your blood more frequently to see how warfarin is working.

The vegetables listed below are known to have high amounts of vitamin K per serving. Although it is important to be aware of foods high in vitamin K, it is also important that you eat a well-balanced diet.

Green Leafy Vegetables



Collard, mustard and turnip greens

Endive, lettuce (Boston, bib, head, red leaf and romaine)

Cruciferous Vegetables


Brussels sprouts



If you want more servings of vegetables in your daily meal plan, choose vegetables that are not high in Vitamin K, such as corn, squash, potatoes, onions, carrots, cucumbers, celery, peppers, pumpkin, and tomatoes.

Herbal teas. Do not start consuming the following herbal teas and supplements because they may affect the INR, causing it to be too high or too low. If you drink tea, black tea (such as orange pekoe tea) is acceptable because it is not high in Vitamin K.

Herbal Teas


Melitot (sweet clover)

Sweet woodruff

Green tea

Mint tea

Tonka beans

Herbal supplements. The following herbal supplements may affect the INR, causing it to be too high or too low. Certain foods like celery, clove, garlic, ginger, and parsley are usually safe if they are used in small amounts in cooking or as a seasoning (these are marked by an asterisk .) They should not be used in the form of a supplement.

Herbal Supplements
Alfalfa/alfalfa sprouts Fenugreek Meadow
Angelica (dong quai) Feverfew Papain
Borage Garlic* Parsley*
Bromelain Ginger* Passion flower
Celery* Gingko biloba Quassia
Clove* Ginseng Quinine
Coenzyme Q-10 (ubiquinone, CoQ10) Green tea Red clover
Danshen Horse chestnut (buckeye, aesulus) Reishi mushroom
Devil’s claw Kelpware Rue
Echinacea Licorice St. John’s wort

Other dietary tips:

  • Avoid grapefruit, pomegranate, and cranberry products.
  • Eat all other foods as you normally would.
  • The following herbal supplements may keep your blood from clotting and should not be used when you are taking anticoagulant medications before surgery:
    • Garlic.
    • Ginger.
    • Gingko biloba.
    • Ginseng.
    • Feverfew.
    • Fish oil.
    • Turmeric.
    • St. Johns Wort.
    • Chondroitin sulfate.
  • Do not take any vitamin supplements that provide more than 100 percent of the Recommended Daily Allowance (RDA). Tell your doctor if you are currently taking more than the RDA of any vitamins (especially vitamins A, C or E).
  • Nutritional supplements including Boost® and Ensure® can also affect warfarin levels. Ask your healthcare provider about the suitability of taking these products.
  • While taking warfarin you should not drink more than one beer, 6 oz of wine, or one shot of alcohol per day.


Some medications may increase the anticoagulant effect of warfarin; others may decrease the effect. You might need to get blood tests more often when you stop, start or increase the dose of medications that are likely to affect the way warfarin works. The dosage of warfarin may need to be adjusted too. Talk to your healthcare provider who manages your warfarin if you have any changes in your other prescription medications.

Medicines that May DECREASE the Effectiveness of Warfarin

Carbamazepine (Tegretol®)

Phenobarbital (Luminal®)

Phenytoin (Dilantin®)

Rifampin (Rifadin®)

Vitamin K Multiple brands

Cholestyramine (Questran®, Questran Light®)

Sucralfate (Carafate®)

This is a sample list and does not include all drugs that may interfere with warfarin.

Medicines that May INCREASE the Effectiveness of Warfarin

Amiodarone (Cordarone®, Pacerone®)

Co-trimoxazole (Bactrim®, Septra®)

Ciprofloxacin (Cipro®)

Clarithromycin (Biaxin®)

Erythromycin Multiple brands

Fluconazole (Diflucan®)

Itraconazole (Sporanox®)

Ketoconazole (Nizoral®)

Lovastatin (Mevacor®)

Metronidazole (Flagyl®)

This is a sample list and does not include all drugs that may interfere with warfarin.

This is NOT a complete listing of medications that can affect the way warfarin works. In fact, many non-prescription medications can also affect how warfarin works. Some examples include acetaminophen (Tylenol®), aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) (such as ibuprofen, naproxen or ketoprofen and cold and cough medicines that contain NSAIDS), antacids, laxatives, or other medications for pain or discomfort.

Always check with the healthcare provider who monitors your warfarin BEFORE taking any over-the-counter medication, herbal product, natural remedy, nutritional supplement or prescription medication from another healthcare provider or dentist. Your healthcare provider may need to adjust your warfarin dose or may recommend another medication or product less likely to interfere with warfarin. Do not stop or start any medications without first talking to your healthcare provider.

Daily activities

  • Be careful when using razors. Use an electric razor or hair-removing creams to lessen the chance of cuts.
  • Use a soft toothbrush. Brush and floss gently to prevent bleeding from the gums.

Illness and emergencies

  • Keep your healthcare provider’s phone number with you in the event of an emergency.
  • Call your healthcare provider if you have any symptoms of illness, such as vomiting, diarrhea, infection, or fever. Illness can change the way warfarin works.
  • Always carry or wear identification that states you are taking warfarin. In an emergency, you may not be able to speak for yourself.
  • Avoid situations at home or work that might lead to an injury. Even minor injuries must be watched for bleeding because warfarin affects clotting. Falls that cause bruising (bleeding under the skin) and cuts from sharp objects are more serious when you are taking warfarin. Call your doctor if you have any injuries from falls or blows to your body or head.


  • Check with your doctor before you travel. You may need to have a blood test and an adjustment to your warfarin dose before you leave.
  • While traveling, carry your medications with you at all times. Do not put medications in checked baggage and do not leave them in the car.
  • If seated for long periods of time during travel, get up and walk if possible or perform foot and leg raises.

What should I do if I cut myself while on warfarin?

If you cut yourself and the cut is small, apply constant pressure over the cut until the bleeding stops. This may take up to 10 minutes. If the bleeding doesn’t stop, continue to apply pressure and go to the nearest emergency room.

If you cut yourself and the cut is large, apply constant pressure and get help immediately either by calling 911 or your local emergency number or by having someone drive you to the nearest emergency room.

What are the side effects of warfarin?

Bleeding is the most common side effect of warfarin and can appear as any of several different symptoms. Call your doctor if you notice any of the following signs of bleeding:

  • Feeling more cold, weak, or tired than usual or looking pale (symptoms of anemia).
  • Bleeding from cuts that won’t stop after applying pressure for 10 minutes.
  • Bleeding from the nose, gums, or ears that will not stop after 10 minutes.
  • A fever or illness that gets worse.
  • Menstrual bleeding (period) that is heavier or lasts longer than normal.
  • Reddish or rusty-colored urine.
  • Bowel movements that look bright red, black or tarry.
  • Bruises that appear without reason or become swollen or painful; purplish spots on your skin.
  • Coughing up blood.
  • Vomiting blood (which may look like coffee grounds).
  • Unusual bleeding from hemorrhoids.
  • Unusual pain or swelling, especially in the joints.
  • Unusual headache.
  • Stomach or abdominal pain.
  • Sudden changes in speech or vision.
  • Numbness/tingling on one side of the face or in the arm.
  • Dizziness.
  • Difficulty breathing.

If you have any of these symptoms, your provider may want to do a blood test, change your dose, stop the medication, or give you medicine to stop the bleeding.

Summary of important points to remember

  • Take your warfarin as instructed and at the same time each day.
  • Have your blood tested as instructed to check how your blood is clotting.
  • Discuss all medications you are taking — even over-the-counter medicines — with your doctor and pharmacist since many drugs can interact with warfarin.
  • Do NOT stop or start taking any medications, herbal products, natural remedies, or nutritional supplements without first talking to the provider who monitors your warfarin medication.
  • Tell anyone providing medical or dental care that you are taking warfarin.
  • Eat about the same amount of vitamin K-containing foods each week, as these foods can affect the way warfarin works.
  • If you forget to take a pill, DO NOT take a double dose. Take the missed dose as soon as possible on the same day. DO NOT take a double dose of warfarin the next day to make up for the missed dose.
  • Watch for signs of abnormal or excessive bleeding and bruising. Call your healthcare provider right away if you suspect something is wrong.
  • DO NOT change warfarin products without first checking with your doctor. Different brands of warfarin products may NOT be identical, and you may need to have your dose checked and adjusted more frequently if you change brands.
  • DO NOT STOP your warfarin even for a minor procedure like dental work without first checking with the doctor who monitors your therapy.
  • It is best to avoid alcohol while taking warfarin.

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Poor patient warfarin knowledge may increase risk of deadly side effects

“The stroke and bleeding complications from warfarin can be fatal,” said Dr Oterhals. “Worldwide warfarin causes the most deaths from drug-related side effects. Patients need to know what foods and drugs have an impact on how warfarin works, and what to do if they have symptoms of an overdose or underdose.”

Warfarin is given to patients at increased risk of blood clots from conditions such as atrial fibrillation or a mechanical heart valve. Blood clots can travel through the blood to the brain and cause a stroke. Warfarin ‘thins the blood’ by slowing down the anticoagulation effect of vitamin K, thereby increasing the time it takes blood to clot and reducing the risk of stroke. Taking too much warfain raises the risk of bleeding.

Patients on warfarin take an individually tailored dose that depends on their genes, usual diet, drugs and physical activity. Initially patients have a daily blood test to check their international normalised ratio (INR) which indicates how long it takes the blood to clot. People not taking warfarin have an INR of around 1 but patients with a mechanical heart valve should have an INR in the range of 2.5 to 3.5 to prevent their body creating a blood clot which could travel to the brain and cause a stroke.

“The goal is to thin the blood enough to prevent a stroke but not too much and cause bleeding,” said Dr Oterhals. “An INR of 3 means it takes 3 times longer to stop a bleeding than it would take someone not on warfarin. If a patient’s INR is below the target range they are at increased risk of thrombosis and above it they are at risk of bleeding complications. Lack of knowledge on what food and drugs interact with warfarin can lead to INR levels outside the therapeutic range which can be dangerous.”

The study included 404 patients with aortic stenosis who were taking warfarin. Nearly two-thirds (63%) took warfarin because they had a mechanical heart valve to treat aortic stenosis and 24% took the drug because they had atrial fibrillation. Patients were 68 years old on average and 70% were men.


Patients received a postal questionnaire with 28 multiple choice questions about warfarin. They answered 18 questions correctly on average but 22% gave correct answers on less than half of the questions. Questions with the least correct answers concerned food and drug interactions and when to call a doctor.

When asked which of the following foods would interfere with warfarin: celery, carrot, coleslaw or green beans, just 25% correctly said coleslaw and most patients answered green beans.

“Patients often think green vegetables have the most vitamin K but that’s not true,” said Dr Oterhals. “Brassica vegetables such as cabbage, broccoli and cauliflower are rich sources. Patients do not have to avoid these foods but they should eat an equal amount every week because the vitamin K will decrease their INR and put them at increased risk of thrombosis or embolism. Patients who like to eat a lot of vitamin K containing foods can take a higher warfarin dosage but they need to be consistent.”

While 80% knew they should go directly to the emergency room if they had nose bleeding that would not stop, only 45% correctly said diarrhoea for more than one day should trigger a visit to the doctor. Some 86% knew that the INR test tells the pharmacist how thick or thin the blood is while taking warfarin.

The study found that increased age was associated with decreasing correct answers. Dr Oterhals said: “We can only speculate why. Younger people tend to seek out information about how to manage their disease while the older generation wants the doctor to tell them what to do.”

She continued: “Motivated patients should be offered an INR testing kit so that they can monitor their levels and adjust the warfarin dose themselves, just as patients with diabetes who use insulin do. It enables patients to travel and try new foods without having to find a clinic to get tested. Patients tell me that hot weather increases their INR while another found out while in Asia that nori decreased his INR.”

Warfarin checklist

  • Diet: keep vitamin K intake consistent and check content of new foods; even small levels eaten in large amounts affect the INR
  • Drugs: antibiotics increase INR; avoid herbal medicines; ask about over the counter drugs
  • Call the doctor: nosebleeds indicate blood is too thin; diarrhoea causes vitamin K loss
  • Exercise: patients who exercise regularly need a higher warfarin dose
  • Be consistent: check how anything out of the ordinary will affect your warfarin.

Dr Oterhals concluded: “Warfarin is a life saving drug but can be deadly if not used carefully. Health professionals have a responsibility to educate patients but unfortunately even cardiac nurses do not know enough.2 There is an urgent need to improve health professionals’ warfarin knowledge so they can educate patients.”

How to Lose Weight While on Coumadin

Doctors often prescribe Coumadin, the brand name for the blood-thinning medication also known as warfarin 1. The medication also has a number of side effects and risks, such as bleeding complications. Vitamin K might affect your blood’s thickness, and because many typical “diet foods” such as spinach and other leafy green vegetables contain vitamin K, you might think you cannot lose weight. Instead of avoiding vegetables, talk with your doctor about the best diet plan for you, and your doctor will work with you so that you can reach your weight loss goals and improve your overall health.

Eat the same amount of vitamin K each day. This way, you can eat salads and other nutritious vegetables, and your doctor can adjust your Coumadin dosage. Vitamin K-rich foods include kale, chard, spinach and collard greens.

Write down what you eat. If you keep track of what you eat, including foods with vitamin K, you can compare your diet to your weight loss 1. This lets you make adjustments to your eating plan such as portion sizes or fat intake to help lower your caloric intake and improve your weight loss.

Talk to your doctor about starting an exercise program. She might recommend that you start off with walking or other beginning exercise regimens, then gradually increase your pace and activities. Starting off slow will help you avoid injuries, as well as prevent complications from health conditions such as heart disease.


Before you make changes to your diet or begin an exercise program, talk with your doctor. She will help you formulate a plan appropriate to your nutritional and physical needs.


Alcohol and cranberry juice might intensify the effects of Coumadin. Talk to your doctor about whether you should limit your intake of these products.

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