What is warfarin?


Generic Name: Warfarin Brand Name(s): Generics only. No brands available.

Know the basics

What is warfarin used for?

Warfarin is an anticoagulant (blood thinner). It reduces the formation of blood clots.

Warfarin is used to prevent heart attacks, strokes, and blood clots in veins and arteries.

Warfarin may also be used for purposes not listed in this medication guide.

How should I take warfarin?

Take warfarin exactly as prescribed by your doctor. Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not take warfarin in larger or smaller amounts or for longer than your doctor tells you to.

Take warfarin at the same time every day, with or without food. Never take a double dose of this medicine.

While using warfarin, you will need frequent “INR” or prothrombin time tests (to measure how long it takes your blood to clot). You may not notice any change in your symptoms, but your blood work will help your doctor determine how long to treat you with warfarin. You must remain under the care of a doctor while using this medicine.

If you have received warfarin in a hospital, call or visit your doctor 3 to 7 days after you leave the hospital. Your INR will need to be tested at that time. Do not miss any follow-up appointments.

Tell your doctor if you are sick with diarrhea, fever, chills, or flu symptoms, or if your body weight changes.

You may need to stop taking warfarin 5 to 7 days before having any surgery or dental work. Call your doctor for instructions. You may also need to stop taking warfarin for a short time if you need to take antibiotics, or if you need to have a spinal tap or spinal anesthesia (epidural).

Wear a medical alert tag or carry an ID card stating that you take warfarin. Any medical care provider who treats you should know that you are using this medicine.

How do I store warfarin?

Warfarin is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store warfarin in the bathroom or the freezer. There may be different brands of warfarin that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush warfarin down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using warfarin?

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies have not been performed on the relationship of age to the effects of warfarin in the pediatric population. Safety and efficacy have not been established.


Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of warfarin in the elderly. However, elderly patients may require caution and an adjustment in the dose, especially those who are at risk of bleeding.

Is it safe to take warfarin during pregnancy or breast-feeding?

There isn’t enough information about the safety of using this medication during pregnancy and breast-feeding. Please always consult with your doctor to weigh the potential benefits and risks before taking this medication.

Know the side effects

What are the side effects of warfarin?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using warfarin and call your doctor at once if you have a serious side effect such as:

  • pain, swelling, hot or cold feeling, skin changes, or discoloration anywhere on your body;
  • sudden and severe leg or foot pain, foot ulcer, purple toes or fingers;
  • sudden headache, dizziness, or weakness;
  • unusual bleeding (nose, mouth, vagina, or rectum), bleeding from wounds or needle injections, any bleeding that will not stop;
  • easy bruising, purple or red pinpoint spots under your skin;
  • blood in your urine, black or bloody stools, coughing up blood or vomit that looks like coffee grounds;
  • pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;
  • dark urine, jaundice (yellowing of the skin or eyes);
  • pain in your stomach, back, or sides;
  • urinating less than usual or not at all;
  • numbness or muscle weakness; or
  • any illness with diarrhea, fever, chills, body aches, or flu symptoms.

Less serious side effects may include:

  • nausea, vomiting, mild stomach pain;
  • bloating, gas; or
  • altered sense of taste.

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.

Know the interactions

What drugs may interact with warfarin?

Warfarin may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Amifampridine
  • Tamoxifen

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Abciximab
  • Acenocoumarol
  • Alefacept
  • Alipogene Tiparvovec
  • Alteplase, Recombinant
  • Amiodarone
  • Amoxicillin
  • Ampicillin
  • Anagrelide
  • Anistreplase
  • Apixaban
  • Aprepitant
  • Aspirin
  • Azithromycin
  • Bivalirudin
  • Blinatumomab
  • Capecitabine
  • Carbenicillin
  • Carboplatin
  • Cefadroxil
  • Cefdinir
  • Cefepime
  • Cefixime
  • Cefotaxime
  • Cefpodoxime
  • Ceftazidime
  • Ceftibuten
  • Ceftizoxime
  • Celecoxib
  • Cephalexin
  • Cephalothin
  • Cephapirin
  • Cephradine
  • Ceritinib
  • Chamomile
  • Ciprofloxacin
  • Citalopram
  • Clarithromycin
  • Clopidogrel
  • Cloxacillin
  • Cobicistat
  • Collagenase, Clostridium histolyticum
  • Cyclophosphamide
  • Dabigatran Etexilate
  • Dabrafenib
  • Dalteparin
  • Danaparoid
  • Dapsone
  • Deferasirox
  • Desvenlafaxine
  • Dicloxacillin
  • Dihydroartemisinin
  • Dipyridamole
  • Doxorubicin
  • Doxorubicin Hydrochloride Liposome
  • Dronedarone
  • Drotrecogin Alfa
  • Econazole
  • Efavirenz
  • Elvitegravir
  • Enoxacin
  • Enoxaparin
  • Entacapone
  • Enzalutamide
  • Eptifibatide
  • Erlotinib
  • Erythromycin
  • Escitalopram
  • Eslicarbazepine Acetate
  • Etoposide
  • Etravirine
  • Fenofibrate
  • Fenofibric Acid
  • Fish Oil
  • Fluconazole
  • Fluorouracil
  • Fluoxetine
  • Fluvoxamine
  • Garlic
  • Gatifloxacin
  • Gemifloxacin
  • Ginkgo
  • Imatinib
  • Infliximab
  • Influenza Virus Vaccine
  • Itraconazole
  • Ketoconazole
  • Ketoprofen
  • Leflunomide
  • Lepirudin
  • Levofloxacin
  • Levomilnacipran
  • Lomitapide
  • Lycium
  • Marijuana
  • Mechlorethamine
  • Mercaptopurine
  • Methicillin
  • Methotrexate
  • Methyl Salicylate
  • Metronidazole
  • Miconazole
  • Milnacipran
  • Mirtazapine
  • Moxalactam
  • Moxifloxacin
  • Nafcillin
  • Nalidixic Acid
  • Nandrolone
  • Naproxen
  • Nilotinib
  • Nintedanib
  • Nitisinone
  • Norfloxacin
  • Noscapine
  • Ofloxacin
  • Oritavancin
  • Oseltamivir
  • Oxacillin
  • Oxandrolone
  • Papaya
  • Paroxetine
  • Peginterferon Alfa-2b
  • Penicillin G
  • Penicillin V
  • Pentosan Polysulfate Sodium
  • Phenindione
  • Phenprocoumon
  • Piperacillin
  • Pixantrone
  • Posaconazole
  • Prasugrel
  • Procarbazine
  • Proguanil
  • Reteplase, Recombinant
  • Rivaroxaban
  • Ropinirole
  • Roxithromycin
  • Sertraline
  • Siltuximab
  • Simvastatin
  • Sitaxsentan
  • St John’s Wort
  • Streptokinase
  • Sulfamethoxazole
  • Sulfisoxazole
  • Tan-Shen
  • Tegafur
  • Telithromycin
  • Tenecteplase
  • Teriflunomide
  • Testosterone
  • Ticarcillin
  • Tinzaparin
  • Tirofiban
  • Tocophersolan
  • Torsemide
  • Urokinase
  • Valproic Acid
  • Venlafaxine
  • Vilazodone
  • Vincristine
  • Vincristine Sulfate Liposome
  • Vindesine
  • Vorapaxar
  • Voriconazole
  • Vortioxetine

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Acarbose
  • Acemetacin
  • Acetaminophen
  • Allopurinol
  • Aminoglutethimide
  • Amitriptyline
  • Amprenavir
  • Apazone
  • Argatroban
  • Atovaquone
  • Avocado
  • Azathioprine
  • Bee Pollen
  • Benorilate
  • Benzbromarone
  • Black Tea
  • Bosentan
  • Bromfenac
  • Butabarbital
  • Butalbital
  • Carbamazepine
  • Carbimazole
  • Cefamandole
  • Cefazolin
  • Ceftriaxone
  • Chitosan
  • Chloral Hydrate
  • Cholestyramine
  • Choline Magnesium Trisalicylate
  • Chondroitin
  • Cimetidine
  • Cisapride
  • Cisplatin
  • Coenzyme Q10
  • Colesevelam
  • Curcumin
  • Cyclosporine
  • Danazol
  • Darunavir
  • Desogestrel
  • Dexamethasone
  • Dexlansoprazole
  • Dextrothyroxine
  • Dienogest
  • Diflunisal
  • Disopyramide
  • Disulfiram
  • Dong Quai
  • Doxepin
  • Drospirenone
  • Duloxetine
  • Esomeprazole
  • Estradiol Cypionate
  • Estradiol Valerate
  • Eterobarb
  • Ethinyl Estradiol
  • Ethynodiol Diacetate
  • Etonogestrel
  • Exenatide
  • Felbamate
  • Fluoxymesterone
  • Fluvastatin
  • Gefitinib
  • Gemcitabine
  • Gemfibrozil
  • Ginger
  • Ginseng
  • Glucagon
  • Glucosamine
  • Glyburide
  • Griseofulvin
  • Heparin
  • Ifosfamide
  • Indomethacin
  • Indoprofen
  • Isoniazid
  • Isoxicam
  • Ivermectin
  • Lactulose
  • Lansoprazole
  • Levamisole
  • Levonorgestrel
  • Levothyroxine
  • Liothyronine
  • Lixisenatide
  • Lopinavir
  • Lornoxicam
  • Medroxyprogesterone Acetate
  • Melatonin
  • Meloxicam
  • Menthol
  • Mephobarbital
  • Mesalamine
  • Mesna
  • Mestranol
  • Methimazole
  • Methylprednisolone
  • Methyltestosterone
  • Methylthiouracil
  • Mitotane
  • Moricizine
  • Nelfinavir
  • Nevirapine
  • Niacin
  • Nilutamide
  • Nimesulide
  • Norelgestromin
  • Norethindrone
  • Norgestimate
  • Norgestrel
  • Omeprazole
  • Orlistat
  • Oxyphenbutazone
  • Pantoprazole
  • Pentoxifylline
  • Phenobarbital
  • Phenylbutazone
  • Phytonadione
  • Piracetam
  • Polyacrylamide
  • Potassium Iodide
  • Prednisone
  • Primidone
  • Propafenone
  • Propoxyphene
  • Propylthiouracil
  • Quetiapine
  • Ranitidine
  • Rifabutin
  • Rifampin
  • Rifapentine
  • Ritonavir
  • Rofecoxib
  • Rosuvastatin
  • Salicylamide
  • Salicylic Acid
  • Salsalate
  • Saquinavir
  • Secobarbital
  • Sodium Salicylate
  • Sodium Thiosalicylate
  • Sorafenib
  • Soybean
  • Soy Isoflavones
  • Soy Protein
  • Stanozolol
  • Sucralfate
  • Sulfasalazine
  • Sulfinpyrazone
  • Sulindac
  • Tenidap
  • Terbinafine
  • Thyroglobulin
  • Thyroid
  • Tibolone
  • Ticlopidine
  • Tigecycline
  • Tolterodine
  • Tramadol
  • Trastuzumab
  • Trolamine Salicylate
  • Valdecoxib
  • Vancomycin
  • Vemurafenib
  • Vitamin A
  • Vitamin E
  • Vorinostat
  • Zafirlukast
  • Zileuton

Does food or alcohol interact with warfarin?

Warfarin may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug, especially:

  • Enteral Nutrition
  • Green Tea
  • High Protein Food
  • Noni Juice
  • Vitamin K Containing Food

What health conditions may interact with warfarin?

Warfarin may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Alcohol abuse, history of;
  • Mental disorders (e.g., psychosis or senility)—Patients with these conditions or those who cannot cooperate should not be given warfarin.
  • Blood disease or bleeding problems;
  • Heart infection;
  • Hypertension (high blood pressure);
  • Spinal anesthesia, recent;
  • Stomach or intestinal ulcer, active;
  • Stroke;
  • Surgery, recent or scheduled (e.g., surgery of the eye, brain, or spine) or
  • Threatened miscarriage—Should not be used in patients with any of these conditions. The risk of bleeding from warfarin may be increased.
  • Catheter insertion;
  • Congestive heart failure;
  • Deep venous thrombosis, heparin-induced;
  • Diabetes;
  • Falls or blows to the body or head;
  • Infection ;
  • Kidney disease;
  • Liver disease;
  • Major surgery, any type;
  • Protein C deficiency (rare hereditary disease), known or suspected;
  • Thrombocytopenia, heparin-induced;
  • Trauma—Use with caution. This medicine may increase your risk of having serious problems

Understand the dosage

The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using this medication.

What is the dose of warfarin for an adult?

Usual Adult Dose for Congestive Heart Failure:

Initial: 2 to 5 mg orally or intravenously once a day for 1 to 2 days, then adjust dose according to results of the International Normalized Ratio (INR) or prothrombin time (PT).

Maintenance: the usual maintenance dose ranges from 2 to 10 mg orally or intravenously once a day.

Usual Adult Dose for Thromboembolic Stroke Prophylaxis:

Initial: 2 to 5 mg orally or intravenously once a day for 1 to 2 days, then adjust dose according to results of the International Normalized Ratio (INR) or prothrombin time (PT).

Maintenance: the usual maintenance dose ranges from 2 to 10 mg orally or intravenously once a day.

Usual Adult Dose for Myocardial Infarction:

Initial: 2 to 5 mg orally or intravenously once a day for 1 to 2 days, then adjust dose according to results of the International Normalized Ratio (INR) or prothrombin time (PT).

Maintenance: the usual maintenance dose ranges from 2 to 10 mg orally or intravenously once a day.

The duration of therapy is usually three months following acute myocardial infarction.

Usual Adult Dose for Prevention of Thromboembolism in Atrial Fibrillation:

Initial: 2 to 5 mg orally or intravenously once a day for 1 to 2 days, then adjust dose according to results of the International Normalized Ratio (INR) or prothrombin time (PT).

Maintenance: the usual maintenance dose ranges from 2 to 10 mg orally or intravenously once a day.

If cardioversion is planned, anticoagulant therapy is usually initiated two to four weeks prior to cardioversion and is continued for two to four weeks following successful cardioversion. If cardioversion is not planned and this patient has complicated atrial fibrillation (atrial fibrillation associated with underlying heart disease) the duration of therapy is typically lifelong.

What is the dose of warfarin for a child?

The dosage has not been established in pediatric patients. It may be unsafe for your child. It is always important to fully understand the safety of the drug before using. Please consult with your doctor or pharmacist for more information.

How is warfarin available?

Warfarin is available in the following dosage forms and strengths:

Tablet 1 mg; 2 mg; 2,5 mg; 3 mg; 4 mg; 5 mg; 6 mg; 7,5 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of warfarin, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Review Date: May 30, 2016 | Last Modified: January 4, 2017

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