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It keeps your bones strong and your blood clotting, but it may also do other things.

Vitamin K is a multitasking nutrient that aids in bone formation and blood clotting, allowing injuries to heal.

Vitamin K is typically obtained through diet. Vitamin K is found primarily in plant-based foods and fermented foods such as sauerkraut. Vitamin K can also be purchased as a dietary supplement. However, unless you have a vitamin K deficiency, it is preferable to get your K from food.

“You should be able to meet your vitamin K needs by eating a balanced diet,” says registered dietitian Julia Zumpano, RD. “It’s important to know which foods are high in this essential vitamin that does so much for our bodies in case your diet is lacking, so you can make any necessary adjustments.”

What exactly is vitamin K?

Vitamin K is a fat-soluble (meaning it dissolves in fat) vitamin that aids in the development and function of your body. There are two kinds of vitamin K, each derived from a different source:

Phylloquinone, or vitamin K1 (pronounced “fil-oh-kwi-nohn”): This type is more common in plant foods, particularly green leafy vegetables like spinach and kale.
Menaquinone, or vitamin K2 (pronounced “men-ah-kwi-nohn”): This less common type can be found in animal foods and fermented foods. This type is also produced by gut bacteria in your body.

What is the function of vitamin K?

Some studies suggest that the benefits of vitamin K go beyond bones and blood. It may alleviate morning sickness while also protecting cognitive (mental) abilities. Vitamin K may even lower your risk of heart disease and death. Recently, researchers discovered that a type of vitamin K acts as an antioxidant, which could help prevent Alzheimer’s disease and other diseases.

More research is needed, but we do know that vitamin K is important for blood clotting as well as bone strengthening.

1. Aids in blood clotting

One of vitamin K’s most important functions is to produce four of the thirteen proteins required for blood clotting. Blood clots prevent injuries or wounds from bleeding, allowing them to heal. The letter “K” is derived from the Danish and German words koagulation (coagulation) and clotting.

This is a significant advantage of vitamin K. However, it also implies that you must exercise caution. People taking blood-thinning medications, such as warfarin (Coumadin®), should not take vitamin K supplements or consume large amounts of vitamin K without first consulting with their healthcare provider. Vitamin K may reduce the effectiveness of these medications.

“In most cases, it’s just a matter of maintaining consistent vitamin and medication levels,” Zumpano says. “An abrupt change can result in dangerous bleeding or blood clots.”

2. Increases bone strength

Vitamin K strengthens your bones by assisting in the production of osteocalcin, which aids in the prevention of low bone density. However, whether it can be used to treat or prevent bone problems remains to be seen.

According to some studies, increasing your daily vitamin K intake lowers your risk of bone fractures and low bone density (osteopenia). Some countries (but not the United States) even prescribe vitamin K supplements to treat osteoporosis.

“A lot of other factors, such as a lack of calcium and vitamin D, can affect bone health,” Zumpano says. “We need more rigorous studies to establish the link before we can recommend vitamin K supplements with confidence.”

What foods contain vitamin K?

Green leafy vegetables like spinach, kale, broccoli, cabbage, and lettuce are high in vitamin K. Fruits (blueberries, figs, and canned pumpkin are good sources) and olive, soybean, or canola oil are also good sources of vitamin K. It can also be found in trace amounts in meat, eggs, and dairy products such as cheese, yogurt, and butter.

“Vegetarians have an advantage when it comes to this essential vitamin,” says Zumpano. “You can definitely get it from other foods, but a plate of leafy greens can’t be beat for vitamin K.”

Consider this: half a cup of collard greens, frozen or boiled, contains 530 micrograms (mcg), or 442% of your daily vitamin K requirement. In addition, a 3-ounce serving of natto (fermented soybeans) contains 850 mcg (708%).

The best time to take vitamin K is after eating fat-containing foods. This allows you to get the most out of it.

How much vitamin K do I require per day?

Your daily vitamin K intake (in micrograms) should be as follows:

Age-Specific Dietary Allowance

6–11 months*, 2.5 mcg

30 mcg, 12 to 23 months*

2 to 18 years old (assigned female at birth, AFAB)

30 to 75 mcg

over the age of 18 (AFAB)

90 mcg
2 to 18 (assigned male at birth, AMAB) (assigned male at birth, AMAB)
30 to 75 mcg

over the age of 18 (AMAB)

120 mcg
75 to 90 mcg *Adequate Intake if Pregnant or Lactating
Dietary Guidelines for Americans 2020–2025

Vitamin K degrades quickly in your body. Any extra leaves in your urine or feces should be disposed of. This means that even if you have a lot of it, it rarely reaches dangerous (toxic) levels.

Is it necessary for me to take vitamin K supplements?

Most multivitamin-mineral supplements, especially those for bone health, contain vitamin K. However, if you get enough of what you need from food, you usually don’t need to take supplements.

If you suspect you are deficient in vitamin K, consult your doctor about next steps. Your symptoms, as well as a blood test, can help confirm the diagnosis and guide treatment.

“There is no shortage of delicious and widely available vitamin K-containing foods,” says Zumpano. “Vitamin K helps with some of our body’s most critical functions, so we need to take it seriously. And that includes eating well in order to live well.”