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

Pregnancy

Warfarin can cause serious birth defects and bleeding in the unborn baby. You must use effective contraception and tell your doctor immediately if you think you are pregnant.

Dietary changes

Vitamin K (found in green leafy vegetables) directly cancels out the effect of warfarin. You must keep your intake of these foods consistent; a sudden increase or decrease can cause your blood to clot or lead to dangerous bleeding.

Interactions with common painkillers

Do not take aspirin or ibuprofen (NSAIDs) while on warfarin unless specifically prescribed, as they significantly increase your risk of life-threatening internal bleeding. Use paracetamol instead.

Food and drink warnings

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

Vitamin K helps your blood to clot, which is the opposite of what warfarin does. You do not need to avoid these foods, but you must keep the amount you eat consistent. A sudden increase or decrease in vitamin K intake can change how your warfarin works.

Cranberry juice and cranberry products

Cranberry juice can 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.

Alcohol

Binge drinking or heavy alcohol consumption can affect how your liver processes warfarin, increasing the risk of bleeding. Stick to moderate, consistent amounts within the recommended daily limits.

Grapefruit juice

Grapefruit juice may increase the effect of warfarin in some people, potentially increasing the risk of bleeding. It is generally advised to avoid large amounts.

Pomegranate juice

Some studies suggest pomegranate juice may interact with warfarin and increase the risk of bleeding. It is best to consume it in moderation or 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.