Warfarin & vitamin K

Keep your vitamin K steady on warfarin

You don't need to stop eating greens. The goal is to eat about the same amount of vitamin K each week, so your warfarin dose can do its job.

Here are some questions you might have:

Why does vitamin K matter if I take warfarin?

Vitamin K helps your blood clot. Warfarin works by blocking how your body uses vitamin K. So a big change in how much vitamin K you eat changes how well your warfarin works, and your INR moves with it. Learn more ↓

Do I have to stop eating leafy greens?

No. Your dose is set around how you usually eat. The goal is to keep the amount steady from week to week, not to cut greens out. Learn more ↓

Which foods are highest in vitamin K?

Cooked leafy greens are the highest: spinach, collard greens, kale, turnip greens, and mustard greens. Brussels sprouts, broccoli, and raw spinach also have a lot. 1 cup of cooked spinach has about 1,020 mcg. Learn more ↓

How much vitamin K do I need a day?

Most adults need about 90 mcg (women) to 120 mcg (men) a day. On warfarin, the exact number matters less than keeping your usual amount about the same each week. Learn more ↓

Does vitamin K hide anywhere besides vegetables?

Yes. Nutrition shakes (like “Boost” and “Ensure”), some multivitamins and calcium chews, green juices and smoothies, and tobacco can all add vitamin K. Learn more ↓

When should I call my care team?

Before big changes to how you eat, when you're sick and eating much less, when your medicines or supplements change, and if you notice unusual bleeding or bruising. Learn more ↓

90 to 120 mcg vitamin Kis what most adults need each day (90 mcg for women, 120 mcg for men). 1 cup of cooked spinach has about 1,020 mcg.

Taking warfarin for AFib, a blood clot, or a heart valve?Same vitamin K, week to week. You typically need a consistent amount of vitamin K from week to week. Love spinach or other foods high in vitamin K? If you don't want to give them up, talk to your dietitian, pharmacist, and doctor about having the same amount every week.

Higher vitamin K foods include:cooked spinach, collard greens, kale, turnip greens, mustard greens, Brussels sprouts, and broccoli

Lower vitamin K foods include:carrots, cauliflower, cucumber, tomatoes, corn, potatoes, bananas, and most fruit

How much do you know?

Want to see how much you know about vitamin K and warfarin before you learn more? Take the quiz! You'll learn about each of these questions on this page.

Vitamin K quiz

How vitamin K and warfarin work

Vitamin K helps your blood clotYour liver uses vitamin K to make clotting proteins. Most of it comes from leafy green veggies.

Warfarin slows clotting downWarfarin (“Coumadin”, “Jantoven”) works by blocking how your body uses vitamin K. That's why the two are linked.

Your INR shows the balanceThe INR blood test measures how long your blood takes to clot. Your care team sets your dose to keep your INR in your target range.

What happens when your vitamin K changes?

Slide to compare this week with your usual week

Steady

Vitamin KAbout the same

Your INRStays in range

RiskYour dose keeps working

Bottom line: the goal is steady, not zero. Eating about the same amount each week keeps your INR, and your dose, steady.

Compare your usual week with this week

Vitamin K in 1 cup (1.0 Veggie Portion). Pick a week, then tap a food to add 1 cup to it. Tap again to add another.

400+ mcg per cup (very high)80 to 399 mcg (medium)under 80 mcg (lower)

Cooked greens shrink. 1 cup of cooked spinach holds many cups of raw leaves, so it has about 8 times the vitamin K of 1 cup raw.

Values are typical amounts from USDA FoodData Central. Your care team may give you your own target.

Out of your usual green? Swap for similar vitamin K

Tap to flip to a swap with a similar amount of vitamin K per cup.

Higher and lower vitamin K foods

From the American Heart Association's list. None of these are off-limits. Higher foods matter most to keep steady; lower foods are less likely to move your INR in normal amounts.

Higher: 60+ mcg per serving

Lower: under 35 mcg per serving

Higher or lower?

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Brussels sprouts

Hidden sources of vitamin K

These can add vitamin K without a single leaf of lettuce. Check with your care team before you start or stop one.

Nutrition shakesDrinks like “Boost”, “Ensure”, and “SlimFast” have added vitamin K.

Multivitamins and calcium chewsSome multivitamins and “Viactiv” calcium chews contain vitamin K. Check the Supplement Facts label.

Green juices and smoothiesBlending or juicing packs many cups of leaves into one glass.

TobaccoCigarettes and chewing tobacco also contain vitamin K.

Steady habits

Keep eating your veggiesCutting greens out isn't the goal. Keep your usual Veggie Portions; your dose is set around them.

Same amount, every weekIf you usually have a spinach salad 3 times a week, keep it at about 3. Spread higher vitamin K foods across the week instead of saving them for one big day.

Tell your care team before big changesA new eating plan, a cleanse, a trip, or lots more salads or smoothies? Check first.

Ask about vitamins and supplementsAlcohol, herbal products, and other supplements can also change your INR. Ask before you start or stop one.

Track your usual greensWrite down the higher vitamin K foods you normally eat and how often, and bring it to your INR check. The printable page has a tracker.

When to call your care team

You're sickVomiting, diarrhea, fever, or eating much less for more than a day or two.

Your medicines or supplements changeNew prescriptions (like antibiotics), vitamins, herbal products, or shakes.

You notice bleeding or bruisingUnusual bruises, nosebleeds, bleeding gums, red or dark urine, or black stools.

You're changing how you eatA new eating plan, fasting, or a big jump in salads or greens.

Signs of a clot or a serious bleed are an emergency. Call 911 for sudden weakness or numbness, trouble speaking, chest pain, shortness of breath, a severe headache, or vomiting blood.

Questions

Can I have a big salad at a party or holiday meal?

One big change can move your INR. If you know a big change is coming (a holiday, a trip, a new diet), ask your care team ahead of time how to handle it.

Do I need to count every microgram?

Usually not. Most people do well by keeping their usual higher vitamin K foods about the same each week. Your care team may give you a more exact target.

Can I take a multivitamin?

Ask your care team first. Many multivitamins contain vitamin K. If you're cleared to take one, take it the same way every day so your intake stays steady.

Do newer blood thinners work the same way?

No. This page is about warfarin, which works against vitamin K. Other blood thinners work differently. Ask your care team what applies to your medicine.

Sources: American Heart Association & StopAfib.org, “Vitamin K in Foods” (2025); University of Iowa Health Care, “Warfarin, Your Diet, and Vitamin K Foods” (2025); USDA FoodData Central (FNDDS); NIH Office of Dietary Supplements, Vitamin K fact sheet. Photos: Wikimedia Commons contributors. This page supports, and never replaces, the plan from your prescriber or anticoagulation clinic.

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