Can I take Warfarin and Aspirin together?

Why this happens

Both medicines work to prevent blood clots but in different ways. Warfarin interferes with the proteins (clotting factors) needed to form a clot, while aspirin stops blood cells called platelets from sticking together. When used together, they have an 'additive' effect, making the blood much thinner than when either drug is used alone. Additionally, aspirin can irritate the lining of the stomach, making stomach ulcers and bleeding more likely.

What you should do

You should only take these two medicines together if they have been specifically prescribed by your doctor (for example, after certain heart procedures). Do not take over-the-counter aspirin or products containing aspirin (like some cold and flu remedies) while on warfarin. If your doctor has prescribed both, watch closely for signs of bleeding, such as dark/tarry stools, coughing up blood, severe bruising, or nosebleeds, and seek medical help immediately if these occur.

Important precautions

Pregnancy

Warfarin can cause serious birth defects and must not be taken during pregnancy. If you are planning a pregnancy or become pregnant, you must seek urgent medical advice to switch to a safer alternative.

Asthma

Aspirin can trigger life-threatening asthma attacks or severe breathing difficulties in some people with asthma. Do not take it if you have ever had a reaction to aspirin or other anti-inflammatory painkillers.

High-risk bleeding activities

Taking these medicines together significantly increases your risk of internal bleeding. You must avoid contact sports or activities with a high risk of head injury, and seek immediate medical help if you have a serious fall or blow to the head.

Food and drink warnings

Foods high in Vitamin K (e.g. spinach, kale, broccoli, Brussels sprouts, asparagus)

Vitamin K helps your blood to clot, which works against warfarin. You do not need to avoid these foods, but you must keep the amount you eat consistent. Sudden changes in your intake can make your warfarin less effective or increase your risk of bleeding.

Alcohol

Avoid binge drinking. Regular heavy drinking or sudden changes in alcohol consumption can affect how warfarin is broken down in your body, increasing the risk of dangerous bleeding. Stick to the recommended low-risk limits.

Cranberry juice and cranberry products

Cranberry juice may increase the effect of warfarin, making your blood too thin and increasing the risk of bleeding. It is best to avoid cranberry products while taking warfarin.

Grapefruit juice

Grapefruit juice can interfere with the enzymes that break down warfarin, potentially increasing the risk of bleeding. It is best to avoid it or keep your intake very small and consistent.

Pomegranate juice

Some evidence suggests pomegranate juice may increase the blood-thinning effect of warfarin. Use with caution.

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.