Warfarin
What it's for
Warfarin thins your blood to prevent harmful blood clots. It is used after a blood clot, for atrial fibrillation, or if you have a mechanical heart valve. Regular blood tests are essential.
Comes as: Tablets
How to take it
- Dose varies for each person based on blood test results (INR).
- Take at the same time each day, usually in the evening.
- Your anticoagulant clinic will adjust your dose.
- Never miss a dose or take extra without advice.
Doses here are typical. Always follow the instructions from your prescriber or on the packet — they come first.
Common side effects
- Bruising more easily
- Bleeding that takes longer to stop
- Nosebleeds
- Blood in your urine (pink or red)
The leaflet inside the packet lists all known side effects.
Important safety points
- Many foods and medicines affect warfarin - check with your pharmacist
- Keep your diet consistent, especially vitamin K foods (green vegetables)
- Avoid alcohol binges
- Carry your anticoagulant alert card at all times
- Tell any doctor or dentist you take warfarin
Get medical help urgently if…
- You have unusual or heavy bleeding that does not stop
- You cough up blood or have blood in your vomit
- You have a severe headache or feel confused
- You have blood in your urine or very dark stools
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.