Medications
Warfarin (Coumadin) Before Surgery
Warfarin is a blood thinner that needs careful timing before surgery — and some people need 'bridging' to stay protected from clots.
Quick answer
Why it matters
Warfarin keeps your blood from clotting. Surgery on fully-thinned blood risks serious bleeding, so it's usually paused — but it takes several days for its effect to wear off, which is why the INR is checked.
People with a mechanical heart valve, a recent clot, or high-risk atrial fibrillation can form a dangerous clot during the gap, so they may be 'bridged' with heparin or low-molecular-weight heparin until just before surgery.
Do not stop without instruction
What to ask your doctor
- Which day do I stop warfarin, and do I need an INR check?
- Do I need bridging injections — and how do I use them?
- When do I restart warfarin after surgery?
- What is my target INR for surgery?
Red flags — call your team
Red flags — call your team
- You have a mechanical heart valve
- You had a recent blood clot (DVT, PE) or stroke
- Unusual bleeding or bruising before surgery
References
- American Society of Regional Anesthesia and Pain Medicine (ASRA) — anticoagulation guidance (warfarin ~5 days + normalized INR). asra.com
- American College of Cardiology / American Heart Association (ACC/AHA) — perioperative anticoagulation. acc.org
Frequently asked questions
How many days before surgery do I stop warfarin?
Usually about 5 days, with an INR check before surgery. Follow your team's exact plan, as some patients need bridging.
What is bridging?
Bridging means using short-acting heparin injections while warfarin is paused, to keep high-risk patients protected from clots until just before surgery.