Warfarin
Warfarin is an oral anticoagulant that makes blood less likely to clot in certain situations, such as atrial fibrillation with higher stroke risk, some clots in veins or lungs, and some heart valve situations when your prescriber recommends it.
This medicine is part of the Blood pressure, cholesterol & related category.
Generic name: warfarin
Quick answers
Short replies to searches people often run before speaking to a clinician. For the overview of what the medicine is used for, see the short summary under the page title above.
What is it for?
Warfarin is an oral anticoagulant that makes blood less likely to clot in certain situations, such as atrial fibrillation with higher stroke risk, some clots in veins or lungs, and some heart valve si…
How long does it take to work?
Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review.
What are common side effects?
Easy bruising or minor bleeding (for example nosebleeds) can happen even when INR is in range.
Can you take paracetamol or ibuprofen with it?
Ask your GP or pharmacist before taking Warfarin with paracetamol or ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
More about what Warfarin is used for
Warfarin is an oral anticoagulant that makes blood less likely to clot in certain situations, such as atrial fibrillation with higher stroke risk, some clots in veins or lungs, and some heart valve situations when your prescriber recommends it.
It requires regular blood tests (INR) so the dose stays in a safe range for you.
How does Warfarin work, and how long does it take to work?
It reduces production of vitamin K–dependent clotting factors in the liver. Effects take days to build and days to wear off, which is why bridging plans exist around surgery.
Dose is individual — the same milligram strength does not mean the same effect in different people.
How and when should you take Warfarin?
Take at the same time each day as directed. Do not skip INR appointments; your clinic or GP uses results to adjust tablets.
If you use a blister pack, check you have taken the correct strength — warfarin comes in several colours in the UK.
What are the common side effects of Warfarin?
Easy bruising or minor bleeding (for example nosebleeds) can happen even when INR is in range. Tiredness or nausea is possible when starting.
Many people on long-term warfarin feel well between checks.
Serious side effects of Warfarin — when to get urgent help
Seek urgent help for major bleeding, head injury while on warfarin, black stools, vomiting blood, sudden severe headache, or neurological symptoms.
Large unexplained bruises or blood in urine also need prompt assessment.
What if you miss a dose of Warfarin?
If you miss a dose, take it as soon as you remember the same day if still appropriate, then contact your anticoagulant clinic for advice — do not double the next day without instruction.
Who should not take Warfarin?
Pregnancy (except rare specialist situations), uncontrolled bleeding, and some conditions need alternative plans. Your clinic assesses falls risk and interactions.
Carry an anticoagulant alert card and tell every healthcare professional you take warfarin.
Can you take paracetamol or ibuprofen with Warfarin? — other interactions
Many antibiotics, antifungals, Amiodarone, and even large diet changes in vitamin K foods can shift INR. Herbal products such as St John’s wort are risky.
Always check before new medicines — community pharmacists can often advise quickly.
Warfarin in pregnancy and breastfeeding
Warfarin is usually avoided in pregnancy; discuss planning and alternatives with your GP or specialist. Breastfeeding advice is individual — ask your prescriber.
Blood tests and monitoring on Warfarin
INR blood tests are essential; frequency is highest when starting or after changes. Your clinic may give a yellow book or digital record to track doses.
What might your GP prescribe instead of Warfarin?
DOACs such as Apixaban are options for some conditions when warfarin is unsuitable — your prescriber compares risks, kidney function, and preferences.
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Frequently asked questions about Warfarin
People also ask — common Google searches
- What is Warfarin used for?
- Warfarin is an oral anticoagulant that makes blood less likely to clot in certain situations, such as atrial fibrillation with higher stroke risk, some clots in veins or lungs, and some heart valve situations when your prescriber recommends it.
- How long does Warfarin take to work?
- Onset varies by condition and dose. Your GP or pharmacist can explain what to expect and when to review. Always follow your prescriber’s follow-up plan.
- Can you take Warfarin with paracetamol or ibuprofen?
- Ask your GP or pharmacist before taking Warfarin with Paracetamol or Ibuprofen. Many adults use paracetamol for short periods when appropriate; NSAIDs such as ibuprofen need extra checks with your other medicines and health conditions.
- What are the side effects of Warfarin?
- Easy bruising or minor bleeding (for example nosebleeds) can happen even when INR is in range. Tiredness or nausea is possible when starting. See the sections below for more detail, including serious side effects and when to seek urgent help.
- What foods affect warfarin?
- Vitamin K–rich foods (for example some leafy greens) are not banned, but very large or sudden changes in intake can alter INR. Aim for a steady pattern and tell your clinic about major diet shifts.
- Can I drink alcohol on warfarin?
- Heavy or binge drinking increases bleeding risk and can disturb INR. If you drink alcohol, discuss sensible limits with your clinician.
Need personalised advice?
Your local pharmacist or GP surgery can help with questions about your medicines, side effects, and alternatives that may be suitable for you.
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Often used with
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