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

Bleeding risk

Both medicines thin your blood. Taking them together significantly increases your risk of severe internal bleeding. You must report any unusual bruising, blood in your urine or stools, or nosebleeds immediately.

Pregnancy

Warfarin can cause serious harm to an unborn baby. You must use effective contraception while taking it and inform your doctor immediately if you think you are pregnant.

Asthma

Aspirin can trigger life-threatening asthma attacks or worsening of breathing in some people with asthma. Do not take this medicine if you have ever had a reaction to aspirin or other NSAIDs.

Children and teenagers under 16

Never give aspirin to children or teenagers under 16 unless specifically prescribed by a doctor. It can cause Reye’s syndrome, a rare but potentially fatal condition affecting the brain and liver.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol when taking these medicines. Alcohol can increase the risk of stomach bleeding when taken with aspirin. For warfarin, alcohol can change how quickly the medicine is processed, making your blood too thin or too thick, which increases the risk of bleeding or blood clots.

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 entirely, but you must keep the amount you eat consistent. A sudden increase or decrease in vitamin K intake can change how well your warfarin works.

Cranberry juice and Goji berries

Cranberry juice and goji berry products can significantly increase the blood-thinning effect of warfarin, leading to a higher risk of bruising or bleeding. It is best to avoid these while taking warfarin.

Grapefruit juice

Grapefruit juice may increase the levels of warfarin in your blood, which can increase your risk of bleeding. It is best to avoid grapefruit juice.

Pomegranate juice

Some evidence suggests pomegranate juice may interact with warfarin and increase the risk of bleeding. It is best to avoid it.

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.