Dietary Advice for People Taking Warfarin Tablets

This leaflet is for people taking warfarin tablets. If you have any concerns with your current medication, please speak to your GP, specialist cardiology nurse or dietitian.

• Do not stop taking warfarin without speaking to your doctor first.
• Do not take more than the prescribed dose.
• Do not give your tablets to others.
• Do not take medicines that contain aspirin unless prescribed by your doctor.

Inform the pharmacist you are taking warfarin when purchasing:

• Healthcare supplements
• Medications over the counter.

Pharmacists need to discuss your treatment and current medication when items are purchased to take alongside warfarin.

Warfarin

Warfarin is used to prevent harmful blood clots from forming within the body. Warfarin works by thinning the blood, so you should be careful not to knock, cut or bruise yourself. The blood thins when the effects of vitamin K are reduced.

How do I know my warfarin is working?

Your doctor will complete a blood test to check your international normalised ratio(INR)is within the target range. The longer your blood takes to clot, the higher your INR, which will determine your warfarin dose.

Dietary advice when taking warfarin

Vitamin K is mainly found in dark green, leafy vegetables. Vitamin K is needed for normal blood clotting, so it’s important to keep your intake of foods containing vitamin K consistent.

Increasing or decreasing foods you eat containing vitamin K could affect how your warfarin works.

Green vegetables are also a source of folate. Folate is an antioxidant which protects the body from damage. Healthy eating guidelines recommend including five portions of fruit and vegetables each day. It is not recommended to exclude foods containing vitamin K altogether.

Foods to limit – choose one portion per day

The foods below are high in vitamin K. Do not have more than one portion of these vegetables a day. A portion is the same as one handful.

• Kale-3 dessert spoons
• Avocado-Half an avocado
• Spinach (boiled)-3 dessert spoons
• Spring greens-4 dessert spoons
• Broccoli-6 –7 small/medium florets
• Green cabbage-4 dessert spoons
• Sprouts-12 sprouts
• Watercress-Quarter bunch
• Asparagus-10 spears
• Coleslaw-2 tablespoons
• Beef liver-4oz (100g).

Examples of foods low in vitamin K – have unlimited portions per day

It’s also recommended to add servings of different vegetables low in vitamin K. If you have more than one portion of the same food, it’ll only count as one of your five-a-day. Below are some examples of fruit and vegetables low in vitamin K.

• Cauliflower-8 florets
• Courgettes-½ a large courgette
• Mushroom-3 –4 dessert spoons
• Peas-3 dessert spoons
• Peppers-½ pepper
• Swede-½ cup (80g)
• Tomatoes-1 medium tomato
• Carrots-3 dessert spoons
• Lettuce-½ cup (80g).

Herbal preparations

Some herbal supplements and teas may interfere with warfarin. People taking warfarin are advised to not drink more than four mugs of green tea per day. Please make sure your GP and dietitian are aware of any supplementation. It is not recommended to take more than one supplement at a time. If you’re unsure whether a supplement is safe to take with warfarin, speak to your GP or pharmacist.

The following products must not be taken with warfarin:

• St John’s Wort
• Danshen
• Cod liver oil
• Ginkgo Biloba
• Grapefruit juice
• Glucosamine
• Cranberry juice
• Cranberry juice tablets/capsules
• Evening primrose oil
• Pomegranate juice.

Multivitamins

These are fine to take, but choose a brand without vitamin K.

Alcohol

Men and women are advised not to drink more than 14 units a week on a regular basis. At least two alcohol-free days are recommended.

The occasional drink of two units or regular intake of one unit should not affect your warfarin. Regular heavy and binge drinking should be avoided. Please see www.drinkaware.co.ukfor more information on units.

Dental health

Please inform your dentist that you are on warfarin. Use a soft toothbrush and take care when using dental floss.

Weight loss

Tell your doctor if you have lost weight since starting warfarin. Your dose may need to be changed.

Contact numbers

Department: 01305 254415
dietetic.secretary@dchft.nhs.uk

About this leaflet

Author: Adapted by the Dietetic Department from University Hospitals Coventry and Warwickshire
Written: June 2023
Approved and updated: March 2026
Review date: March 2029
Edition: v2

Reference: HIC/LFT/2320/1