Vitamin K

Medically Reviewed by Jabeen Begum, MD on June 07, 2024
5 min read

Vitamin K plays a key role in helping the blood clot, which prevents excessive bleeding. Unlike many other vitamins, vitamin K is not typically used as a dietary supplement.

Vitamin K vs. vitamin K2

Vitamin K is actually a group of compounds, with the most important ones being vitamin K1 and vitamin K2. Vitamin K1 is obtained from leafy greens and some other vegetables. Vitamin K2 is a group of compounds largely obtained from meats, cheeses, and eggs and synthesized by bacteria.

Vitamin K1 is the main form of vitamin K supplement available in the U.S.




Vitamin K's key role is to help heal injuries through blood clotting and strengthen bones. Researchers suggest that this vitamin has other benefits too, such as easing morning sickness and protecting cognitive functions, including thinking, memory, learning, and organizing skills. It may also help protect heart health.

Blood clotting

Vitamin K makes four proteins among the 13 that are needed for blood clotting (coagulation).

Strengthens the bone

By making the protein osteocalcin, vitamin K keeps your bones strong and helps you to avoid low bone density. But it's still unclear if vitamin K can treat or prevent bone problems. Some studies suggest that getting more vitamin K daily can lower your chances of bone fractures and low bone density (osteopenia).

May protect heart health

It's not exactly known how vitamin K protects arteries, but it seems to lower inflammation and prevent calcium buildup. People who consume more vitamin K1 are less likely to be admitted to the hospital for heart disease due to clogged arteries. Vitamin K2 also helps lower your chances of heart disease, though this finding is less certain because vitamin K2 comes in many forms that behave differently in the body.

Low levels of vitamin K can raise the risk of uncontrolled bleeding. While vitamin K deficiencies are rare in adults, they are very common in newborn infants. A single injection of vitamin K for newborns is standard. Doctors also use vitamin K to counteract an overdose of the blood thinner Coumadin.

While vitamin K deficiencies are uncommon, you may have a higher chance if you:

  • Have a disease that affects absorption in the digestive tract, such as Crohn's disease or active celiac disease
  • Take drugs that interfere with vitamin K absorption
  • Are severely malnourished
  • Drink alcohol heavily

In these cases, a health care provider might suggest vitamin K supplements.

Uses of vitamin K for cancer, morning sickness, removal of spider veins, and other conditions are unproven. Learn more about vitamins K2 and D3 as well as which foods pack the highest amount.

Symptoms of vitamin K deficiency

Symptoms of low levels of vitamin K may include:

  • Feeling sleepy
  • Throwing up
  • Seizures
  • Bruising
  • Small red spots (petechiae)
  • Nosebleeds
  • Yellowing of the skin and eyes (jaundice)
  • Pale skin
  • Bloody, dark, and sticky poop

Most people get enough vitamin K from their diets. The recommended daily intake of vitamin K (both from food and other sources) is listed below.


Adequate Intake

Children 0-6 months

2 micrograms/day

Children 7-12 months

2.5 micrograms/day

Children 1-3

30 micrograms/day

Children 4-8

55 micrograms/day

Children 9-13

60 micrograms/day

Girls 14-18

75 micrograms/day

Women 19 and up

90 micrograms/day

Women, pregnant or breastfeeding (19-50)

90 micrograms/day

Women, pregnant or breastfeeding (under 19)

75 micrograms/day

Boys 14-18

75 micrograms/day

Men 19 and up

120 micrograms/day

There have been no adverse effects of vitamin K seen with the levels found in food or supplements. However, this does not rule out danger with high doses. Researchers have not set a maximum safe dose.

You'll find Vitamin K mostly in food, but you can also get it through:

Vitamin K oral supplements. You can find vitamin K in most multivitamin/mineral supplements. It's also available in supplements that have only vitamin K or are combined with calcium, magnesium, vitamin D, or other nutrients.

Vitamin K injection. Your doctor will offer a vitamin K shot for your newborn after birth. It helps your child avoid a condition called vitamin K deficiency bleeding (VKDB).

Vitamin K drops for newborns. If you don’t want your newborn to get a shot, you can use vitamin K drops. They'll get three doses of vitamin K within 6 weeks after they're born.

Good natural food sources of vitamin K include:

  • Vegetables such as spinach, asparagus, and broccoli
  • Legumes such as soybeans

You can also meet your daily requirement with foods that have lesser amounts of vitamin K:

  • Eggs
  • Strawberries
  • Meat like liver
  • Pumpkin
  • Pine nuts
  • Iceberg lettuce

Side effects of oral vitamin K at suggested doses are rare. Less common side effects include:

  • Loss of appetite
  • Less movement or activity
  • Trouble breathing
  • Enlarged liver
  • Body swelling
  • Irritability
  • Stiff muscles
  • Pale skin
  • Yellow eyes or skin (jaundice)

Interactions. Many drugs can interfere with the effects of vitamin K. They include antacids, blood thinners, antibiotics, aspirin, and drugs for cancer, seizures, high cholesterol, and other conditions.

Who should avoid vitamin K supplements?

You should not use vitamin K supplements unless your health care provider tells you to. People using Coumadin for heart problems, clotting disorders, or other conditions may need to watch their diets closely to control the amount of vitamin K they take in. They should not use vitamin K supplements unless advised by their health care provider.

Vitamin K is a group of compounds essential for blood clotting, bone health, and possibly heart health. You'll find it in leafy greens and some vegetables (vitamin K1) and in meats, cheeses, and eggs (vitamin K2). Adults rarely have vitamin K deficiency, but it can happen with certain medications or conditions. Newborns have a higher chance of having vitamin K deficiency because of low transfer from the placenta and breast milk. Vitamin K is available in multivitamins, single-nutrient supplements, injections, and drops. You can also get it through various foods. Although the side effects of vitamin K are rare, they can include trouble breathing and liver issues. 

Is vitamin K the same thing as potassium?

No, they're different. Potassium is just a mineral with a “K” as a symbol on the periodic table, while vitamin K is a vitamin.