Warfarin is a type of medication that a healthcare professional may prescribe for people with certain health conditions or risks.
There are steps that you can take to help make warfarin as effective as possible. Although there is no specific “warfarin diet,” certain foods and drinks can make warfarin less effective.
In this article, we’ll:
- tell you how foods you eat can affect how well your warfarin works
- give you an idea of which foods to avoid
- tell you other important information about warfarin
Warfarin is an anticoagulant, or blood thinner. A healthcare professional may prescribe it to:
- people who have previously experienced a heart attack
- those with an irregular heartbeat
- people with mechanical heart valves
It’s also used to prevent blood clots from forming in your blood vessels. In addition, it treats blood clots if they do form by preventing them from getting larger.
When clots are smaller, they’re more likely to dissolve on their own. If blood clots are not treated, they can lead to stroke, heart attack, or other serious conditions.
Warfarin interferes with the way a certain clotting factor helps your blood to clot. A clotting factor is a substance that helps the blood clump together to form a clot. There are
The type of clotting factor that warfarin interferes with is called the vitamin K-dependent clotting factor. Warfarin works by decreasing the amount of vitamin K in your body. Without enough vitamin K to use, the vitamin K-dependent clotting factor can’t help your blood to clot like it usually does.
Your body makes vitamin K, but it also gets it from certain foods you eat. One way you can help warfarin work its best is by avoiding big changes in the amount of vitamin K you get through food.
Warfarin works because you usually have consistent levels of vitamin K in your body. If you change the amount of vitamin K you’re getting through food, it can change the levels of vitamin K in your body. This can affect how warfarin works for you.
If you suddenly start eating foods that have more vitamin K while you take warfarin, you may make warfarin less effective. If you suddenly start eating foods that have less vitamin K while you take warfarin, you may increase your chances of side effects from warfarin.
Foods that are rich in vitamin K include leafy vegetables. These may make warfarin less effective. Examples include:
- brussels sprouts
- collard greens
- mustard greens
- red cabbage
- green lettuce
You should also avoid drinking:
- green tea
- grapefruit juice
- cranberry juice
Green tea contains vitamin K and could lower the effectiveness of warfarin. Drinking grapefruit juice, cranberry juice, and alcohol during treatment with warfarin can increase your risk of bleeding.
There are a variety of foods that are low in vitamin K that can help you create and enjoy a well-balanced diet.
Some vegetables and fruits low in vitamin K include:
- sweet corn
- sweet potatoes
- cucumbers (raw)
For a comprehensive list of foods containing vitamin K, visit the U.S. Department of Agriculture’s
Substances other than food can also affect how well warfarin works. This effect is called an interaction. Sometimes these interactions can increase your risk of side effects from warfarin.
While you take warfarin, your doctor will check your blood regularly to see how well the drug is working for you.
Certain medications, supplements, and herbal products can affect how well warfarin works. Tell your doctor all the medications you’re taking before you start taking warfarin.
Some medications that can interact with warfarin include:
- antibiotics such as ciprofloxacin or fluconazole
- certain birth control pills
- certain drugs for seizures
- anti-inflammatory drugs such as ibuprofen
- antidepressants such as fluoxetine
- other blood thinners such as aspirin, clopidogrel, or heparin
- certain antacids
Supplements and herbal products that can interact with warfarin include:
Interactions with food, medications, and other substances can also increase your risk of side effects from warfarin. The most common side effects of warfarin include:
- allergic reactions
- gastrointestinal disorders
- hair loss
- itchy skin
- inflammation of your blood vessels
- liver or gall bladder disorders
Some serious side effects of warfarin can include excessive bleeding from wounds and death of skin tissue. This is caused by small blood clots that block the flow of oxygen to your skin. Toe pain can be a symptom of skin death.
Check your toes often, especially if you feel discomfort, and contact your doctor as soon as possible if you experience pain.
Your international normalized ratio (INR) is found via a blood test called the prothrombin time test. This is a number that your healthcare professional will monitor if you’re taking warfarin to see how quickly your blood clots.
The normal range varies from person to person, but for those taking a blood thinner, your INR number should be between 2 and 3.
To help keep your INR in this range, it’s important to:
- Follow your doctor’s recommendations and take your medication as prescribed. Also, make sure your doctor is aware of all the medications you’re currently taking.
- Keep track of the amount of vitamin K you consume. Don’t suddenly increase or decrease the amount of vitamin K-rich foods or drinks you eat or drink.
- Avoid trying a new diet or taking a new herbal product or supplement. Always speak with your doctor before incorporating something new into your diet.
You should always try to make a habit of eating nutrient-rich foods, but it’s especially important to pay attention to what you eat and how much you eat while you take warfarin.
The following rules of thumb can help you ensure that warfarin works its best for you:
- Don’t make any big changes to your diet, especially in the amount of vitamin K-rich foods.
- Avoid green tea, cranberry juice, grapefruit juices, and alcohol.
- Tell your doctor about other medications, supplements, and herbal products you take.
Following these tips can help you avoid interactions and keep your nutrient levels consistent. This can help make warfarin as effective as possible and help reduce your risk of side effects.