Can I take Warfarin and Vitamin K together?

Why this happens

Warfarin works by blocking the way your body uses Vitamin K to make blood-clotting factors. If you suddenly increase your Vitamin K intake, it acts as an 'antidote' to the warfarin, allowing your blood to clot more easily than your doctor intended.

What you should do

You do not need to avoid Vitamin K entirely, but you must keep your intake consistent. Do not make sudden changes to your diet (such as suddenly eating lots of spinach, kale, or broccoli) or start any new multivitamins without talking to your doctor. Your warfarin dose is adjusted based on your usual diet; if your diet changes, your dose may need to be changed too.

Important precautions

Bleeding risk

Warfarin increases your risk of serious bleeding. You must seek immediate medical attention if you have a fall, a head injury, or notice signs of internal bleeding such as dark/tarry stools or coughing up blood.

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.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking warfarin. Alcohol can affect how your liver processes the medicine, which may increase your risk of bleeding or cause your INR levels to become unstable. If you do drink, keep it to a minimum and do not binge drink.

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.