Warfarin: Uses, How It Works, Medicines
Warfarin is a prescription blood thinner (anticoagulant) used to treat and prevent harmful blood clots. It also lowers the risk of stroke in some people with heart conditions. Bleeding is its main risk, so regular INR blood tests are needed. It should never be started, stopped or changed without a doctor's advice.
Also known as: Warfarin sodium, Warfarin tablet, Warfarin 5 mg, Warfarin 2 mg, Warfarin 1 mg, Coumadin, Uniwarfin
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
How does Warfarin work?
Warfarin blocks the way the body re-uses vitamin K, which the liver needs to make active clotting proteins. The blood then takes longer to clot, and a blood test called the INR is used to check the effect.
How to take Warfarin
Follow the label or your doctor's advice. The dose is different for each person and is adjusted using INR blood tests. It is usually taken once a day at the same time.
Side effects of Warfarin
Most people take warfarin without serious problems. Some side effects are mild, but a few need medical help.
Uncommon or mild
- Easy bruising
- Nosebleeds or bleeding gums
- Bleeding from cuts that takes longer to stop
- Heavier periods
Rare but serious: get medical help
- Blood in the urine or stool, or vomiting or coughing up blood. Get medical help immediately
- A sudden severe headache, confusion, trouble speaking or weakness. Call 112 or get emergency help immediately
- Any head injury, even if you feel well
- A painful skin rash or dark patches on the skin
- Swelling of the face, lips or throat, or difficulty breathing
Who should be careful
Some people need to check with a doctor before taking warfarin, or need extra care while taking it.
When the label says not to use it
- Allergy to warfarin or any ingredient of the tablet
- Active serious bleeding
- Pregnancy, unless a specialist has advised it
- Never stop it or change the dose on your own
- Stomach ulcer, liver or kidney disease, high blood pressure, recent stroke or planned surgery
- Pregnancy: it can harm the baby and is usually avoided; tell your doctor at once
- Breastfeeding: generally allowed; tell your doctor if your baby has unexplained bruising
- Tell every doctor and dentist that you take it; carry an alert card
Medicines and things that interact with Warfarin
Tell your doctor or pharmacist about everything you take, including herbal remedies and medicines bought over the counter.
- Aspirin and NSAID painkillers such as ibuprofen: raise the risk of bleeding
- Other blood thinners: the risk of bleeding rises
- Many antibiotics, antifungals, antidepressants, heart and ulcer medicines and statins: can change its effect
- St John's wort, vitamin K, cranberry and grapefruit juice, large amounts of alcohol, and big changes in vitamin K-rich foods: can change its effect
If someone takes too much
Taking more than prescribed is dangerous because it can cause serious bleeding. Call 112 or go to the nearest hospital at once and take the pack and alert card with you.
Regulatory status in India
Approved for sale in India as a prescription medicine. Single-ingredient warfarin is not known to be on the CDSCO list of medicines banned under section 26A of the Drugs and Cosmetics Act. Fixed-dose combinations that contain warfarin with other medicines may be treated differently, so check the ingredient list on the pack.
Type of medicine
Warfarin belongs to this type of medicine.
Medicines that contain Warfarin
These medicines sold in India contain Warfarin. They are listed A to Z, not ranked.
- Uniwarfin 5 · 5 mg tablet
What is Warfarin used for?
Medicines that contain Warfarin are used for these conditions.
Other medicines of the same type
These active ingredients are of the same type as Warfarin.
Common questions
What is warfarin used for?
It is used to treat and prevent harmful blood clots, such as in the leg or lung, and to lower the risk of stroke in some people with an irregular heartbeat or mechanical heart valves. A doctor decides whether it suits you.
Why does warfarin need INR blood tests?
The INR shows how long your blood takes to clot. Warfarin works differently for each person and is affected by food, illness and other medicines, so the test keeps the effect safe. Do not miss tests.
What should I do if I bleed or hit my head on warfarin?
Get medical help straight away for bleeding that will not stop, blood in urine or stool, vomiting blood, or any head injury, even if you feel fine. A sudden severe headache or confusion is an emergency.
Can I stop warfarin if I feel well?
No. Do not stop on your own, because stopping can raise the risk of a clot or stroke. Talk to your doctor, who decides whether any change is suitable.
Does food affect warfarin?
Yes. Leafy green vegetables are rich in vitamin K and can change its effect. You can still eat them, but keep your diet steady and ask your warfarin clinic. Avoid cranberry and grapefruit juice and large amounts of alcohol.
Is Uniwarfin the same as warfarin?
Uniwarfin is a brand name. The tablet contains warfarin. Never switch brand or strength without asking your doctor, because the INR may need rechecking.
Sources
- Warfarin: an anticoagulant medicine. NHS (UK)
- Blood clots and deep vein thrombosis (DVT). NHS (UK)
- ATC/DDD Index: B01AA03 warfarin. WHO Collaborating Centre for Drug Statistics Methodology