Can I take Warfarin and Amoxicillin together?

Why this happens

Warfarin works by blocking vitamin K, which the body needs to clot blood. Some of this vitamin K is produced by 'friendly' bacteria in your gut. Amoxicillin can kill these bacteria, leading to lower vitamin K levels and making the warfarin effect much stronger. Amoxicillin may also slightly interfere with how the liver processes warfarin.

What you should do

You must inform the healthcare professional who manages your warfarin (such as your GP or anticoagulant clinic) that you have started amoxicillin. They will likely need to perform an extra blood test (INR test) within 3 to 5 days of starting the antibiotic to check if your dose needs adjusting. Seek medical help immediately if you notice blood in your urine or stools, or if you have a nosebleed that won't stop.

Using other medicines

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.