When is warfarin prescribed

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A single copy of these materials may be reprinted for noncommercial personal use only. This content does not have an English version. This content does not have an Arabic version. See more conditions. Warfarin side effects: Watch for interactions. Products and services. Warfarin side effects: Watch for interactions Although commonly used to treat blood clots, warfarin Jantoven can have dangerous side effects and put you at risk of heavy bleeding.

By Mayo Clinic Staff. Thank you for Subscribing Our Housecall e-newsletter will keep you up-to-date on the latest health information. Please try again. Something went wrong on our side, please try again. Show references Warfarin: Drug information. Accessed Jan. Hull RD, et al. The risk for bleeding while taking warfarin is also higher for people participating in an activity or sport that may result in serious injury.

If you experience any of the following symptoms, call your doctor immediately: pain, swelling, or discomfort, bleeding from a cut that does not stop in the usual amount of time, nosebleeds or bleeding from your gums, coughing up or vomiting blood or material that looks like coffee grounds, unusual bleeding or bruising, increased menstrual flow or vaginal bleeding, pink, red, or dark brown urine, red or tarry black bowel movements, headache, dizziness, or weakness.

Some people may respond differently to warfarin based on their heredity or genetic make-up. Your doctor may order a blood test to help find the dose of warfarin that is best for you. Warfarin prevents blood from clotting so it may take longer than usual for you to stop bleeding if you are cut or injured. Avoid activities or sports that have a high risk of causing injury.

Call your doctor if bleeding is unusual or if you fall and get hurt, especially if you hit your head. Keep all appointments with your doctor and the laboratory. Your doctor will order a blood test PT [prothrombin test] reported as INR [international normalized ratio] value regularly to check your body's response to warfarin. If your doctor tells you to stop taking warfarin, the effects of this medication may last for 2 to 5 days after you stop taking it.

Your doctor or pharmacist will give you the manufacturer's patient information sheet Medication Guide when you begin treatment with warfarin and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions.

Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic replacement or mechanical heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis swelling and blood clot in a vein and pulmonary embolism a blood clot in the lung. Warfarin is in a class of medications called anticoagulants 'blood thinners'.

It works by decreasing the clotting ability of the blood. Warfarin comes as a tablet to take by mouth. It is usually taken once a day with or without food. Take warfarin at around the same time every day.

Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take warfarin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Call your doctor immediately if you take more than your prescribed dose of warfarin. Your doctor will probably start you on a low dose of warfarin and gradually increase or decrease your dose based on the results of your blood tests. This includes before you have vaccinations and routine sessions with the dental hygienist. Your doctor may advise you to stop taking warfarin or reduce your dose for a short time before your treatment.

If you have lost your alert card or were not given one, ask your doctor or anticoagulant clinic. It's not a problem if you occasionally forget to take a dose at the correct time. But if you forget often, your blood could be affected — it might become thicker and put you at risk of having a blood clot.

If you do not remember until the next day, skip the missed dose and take your normal dose at the usual time. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine. If you take an extra dose of warfarin, call your anticoagulant clinic straight away. If you take more than 1 extra dose of warfarin, you're at risk of serious bleeding. If you need to go to hospital, take the warfarin packet or leaflet inside it, plus any remaining medicine, with you.

If you have a yellow book, take that too. While warfarin has enormous benefits, the downside is that it can make you bleed more than normal. This is because while you're taking warfarin, your blood will not clot as easily.

You're more likely to get bleeding problems in the first few weeks of starting warfarin treatment and when you're unwell - for instance, if you have flu, are being sick vomiting or have diarrhoea. Apart from the risk of bleeding, warfarin is a very safe medicine. It's safe to take for a long time, even many years. It's usual to bleed more easily than normal while you're taking warfarin. If it happens, keep taking the warfarin, but tell your doctor if the bleeding bothers you or does not stop.

While you're taking warfarin, be careful when you do activities that might cause an injury or a cut or bruising. Like all medicines, warfarin can cause side effects, although not everyone gets them. These side effects are usually mild, but talk to your doctor or pharmacist if these symptoms bother you or do not go away:.

Call a doctor straight away if you develop any of these serious side effects:. In rare cases, warfarin can cause a serious allergic reaction anaphylaxis. These are not all the side effects of warfarin. For a full list, see the leaflet inside your medicines packet. It's very important to keep your diet stable. This means your dose of warfarin is more likely to stay the same.

Any big changes in what you eat or drink can change how your body responds to warfarin. Speak to your doctor or nurse before changing what you eat - for example, before you go on a diet to lose weight. Foods containing a lot of vitamin K can interfere with how warfarin works. It's important that you eat foods containing vitamin K, so rather than leaving them out of your diet, make sure you eat similar amounts of them regularly.

This will mean the level of vitamin K in your blood stays fairly constant and makes it more likely that your INR level stays stable. Do not drink cranberry juice, grapefruit juice or pomegranate juice while you're taking warfarin. It can increase the blood-thinning effect of your medicine. It can be harmful to the baby, particularly during the first 12 weeks of pregnancy. Many medicines and supplements can interfere with warfarin.

This can make you more likely to have bleeding. You might need a blood test to check the other medicine is not affecting how your blood clots. If you're taking warfarin, tell your doctor before starting to take these medicines:. It's safe to take paracetamol while you're on warfarin.

But take a lower dose of 1 tablet mg at a time. Do not take more than 4 tablets 4 x mg over a hour period. Taking more paracetamol than this may make your blood slower at clotting. This puts you at risk of bleeding. If you're still in pain after taking paracetamol for 3 or 4 days, speak to your pharmacist or doctor. Do not take aspirin and ibuprofen while you're taking warfarin unless a doctor has said it's OK to. They increase the chance of bleeding. Do not take St John's wort, the herbal remedy for depression, while you're taking warfarin.

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements. Warfarin is a type of medicine known as an anticoagulant. It makes your blood clot more slowly. Blood clotting is a complicated process involving substances called clotting factors.

Clotting factors are made by the liver and help stop bleeding. They work with blood cells called platelets that trigger the clotting process to make sure your blood clots properly. To make some of the clotting factors, the liver needs a good supply of vitamin K.

Warfarin blocks the liver from using vitamin K to make clotting factors. This thins your blood, so it takes longer to clot. Therefore, patients who fill U. We advise U. Foreign drugs may use identical or potentially confusing brand names for products with active ingredients that differ from U. Warfarin has many foreign brand names Table 1. Patients who do fill prescriptions abroad should ensure the accuracy and quality of the medication dispensed.

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. 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.

An unusual headache or a headache that is more severe than usual may signal intracerebral bleeding. If you experience the following signs of bleeding, you should call or your healthcare provider immediately:. Some simple changes to decrease the risk of bleeding while taking warfarin include the following:. Changes in daily living can affect the INR. 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.

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. 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.