What Is a Vitamin K Deficiency?

Medically Reviewed By Adam Bernstein, MD, ScD
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The fat-soluble vitamin K helps blood clot and maintains bone health. A deficiency in the nutrient could lead to significant bleeding and osteoporosis. A vitamin K deficiency is uncommon in healthy adults because most get it from green vegetables and bacteria in the intestine. However, newborns are at risk and may receive a vitamin K injection at birth. Sources of vitamin K include dark leafy greens and fermented plant foods.

Read on to learn what vitamin K is, its role in the body, and the signs and symptoms of a deficiency. This article also explains what foods can increase levels of vitamin K.

What is vitamin K?

there is a photo of leafy greens, which are high in vitamin K
Christine Han/Stocksy United

The “K” comes from the German word “Koagulation,” meaning to clot blood and prevent hemorrhage.

The nutrient is part of a group of fat-soluble vitamins, including:

  • Vitamin K1, phylloquinone: Aids in blood clotting.
  • Vitamin K2, menaquinone-4 (MK-4), and vitamin K2, menaquinone-7 (MK-7): Your body synthesizes these vitamins and more in your bone, cartilage, and blood vessel walls. Vitamin K2 helps transport calcium, preventing calcium deposits from building up in the lining of blood vessel walls and helping improve bone density.
  • Vitamin K3, menadione: Vitamin K3 is a potentially toxic manufactured form of vitamin K. Researchers are studying vitamin K3 to find out whether it can help with prostate and hepatocellular cancer therapy and some skin disorders.

Sex and gender exist on spectrums. This article uses the terms “female” and “women” when discussing people assigned female at birth to reflect language that appears in source materials.

Learn more about the difference between sex and gender here.

How much vitamin K should we have per day?

According to the National Institute of Health (NIH), the table below shows how much vitamin K is required daily in micrograms (mcg) to ensure nutritional adequacy or adequate intake (AI), depending on age and sex.

From birth up to 6 months 2.0 mcg2.0 mcg
7-12 months2.5 mcg2.5 mcg
1-3 years30 mcg30 mcg
4-8 years55 mcg55 mcg
9-13 years60 mcg60 mcg
14-18 years75 mcg75 mcg
19+ years120 mcg90 mcg

What are the benefits of vitamin K?

Research shows that your body needs vitamin K to produce proteins that help blood clot and maintain calcium levels.

Adequate levels of vitamin K may contribute to improved cognition in older adults.  

Lowering the risk of cardiovascular diseases

Your body uses vitamin K in proteins that may help lower calcification. Vascular calcification is an active process that can cause cardiovascular disease.

Visit our hub to learn more about heart health.

Lowering the risk of osteoporosis

Some studies link vitamin K intake to contributing to a higher bone mineral density and lower hip fracture incidence.

One study of Japanese patients suggested that those who increased their levels of vitamin K2 by eating fermented soybeans had fewer hip and vertebra fractures. Other studies, however, did not show an improvement in bone density.

Read more about osteoporosis.

Lowering the risk of arthritis

Research suggests that insufficient levels of vitamin K may lead to mineral deposits in your cartilage and bones. These deposits may contribute to the symptoms of osteoarthritis.

Evidence suggests that supplementing vitamin K2 may reduce inflammation resulting from arthritis.

Visit our hub to learn more about arthritis.

Improving cognition

Vitamin K helps your body produce proteins that play a role in the peripheral and central nervous systems. So increased levels of vitamin K may improve cognitive function in healthy older adults.

Visit our hub to learn more about brain health.

Lowering the risk of diabetes

One study showed that taking a vitamin K supplement of 10 mcg a day reduces the risk of developing diabetes by 7%.

Visit our hub to learn more about diabetes.

What are the sources of vitamin K?

Sources of vitamin K include green vegetables and fruits. K1 is predominately found in green vegetables and plant chlorophyll.

Sources of vitamin K1

Sources of vitamin K1 include:

  • leafy greens
  • asparagus
  • Brussels sprouts
  • grapes
  • kiwi
  • avocado

Sources of vitamin K2

Sources of vitamin K1 include:

Bacteria in your gut synthesize vitamin K2. The top sources of vitamin K are those in which bacteria are part of the production process of food.

  • nattō, which is fermented soy
  • sauerkraut
  • dairy products, especially hard cheeses

Visit our hub to learn more about food, nutrition, and diet.

What are the signs of a vitamin K deficiency?

The most typical sign of a vitamin K deficiency is usually bleeding, but other signs may occur, such as:

  • bruising easily
  • gastrointestinal hemorrhage
  • hemorrhagic disease of the newborn

What causes a vitamin K deficiency?

A vitamin K deficiency is uncommon in healthy adults but can occur in newborns. Vitamin K transport across the placenta is usually weak, increasing the risk of a deficiency in newborn babies.

Gastrointestinal disorders

People with malabsorption syndromes and other gastrointestinal disorders, such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome, may not absorb sufficient vitamin K.


Antibiotics can destroy vitamin K-producing bacteria in the gut. You can potentially develop a vitamin K deficiency if you also have a low vitamin K intake.

This is more likely with cephalosporin antibiotics, such as Cefobid. These antibiotics might also inhibit the action of vitamin K in the body.

How do you treat a vitamin K deficiency?

You can treat a vitamin K deficiency by increasing your intake through diet or supplementation.

What are the complications of a vitamin K deficiency?

A vitamin K deficiency may cause complications in newborn babies, as it does not cross over from the placenta well. During the first few weeks of life, vitamin K deficiency can lead to vitamin K deficiency bleeding (VKDB).

This is associated with bleeding in the umbilicus, gastrointestinal tract, skin, nose, and other areas. To prevent VKDB, the American Academy of Pediatrics recommends administering a single intramuscular dose of 0.5 to 1 milligram (mg) of vitamin K1 at birth.

Is there a risk of having too much vitamin K?

Current research does not show that high doses of oral vitamin K1 or vitamin K2 are harmful. However, there is evidence that IV administration of vitamins can contribute to bronchospasm and cardiac arrest.

Certain medications can interfere or interact with vitamin K. These can include:

  • anticoagulants such as warfarin
  • antibiotics
  • bile acid sequestrants, which reduce cholesterol levels
  • orlistat, a weight loss drug


Vitamin K contributes to blood clotting and maintains bone health. A vitamin K deficiency is uncommon in adults but can occur in newborns.

You can help maintain your levels of vitamin K by including green leafy vegetables, fruits, nuts, fermented foods, meats, and cheeses in your diet.

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Medical Reviewer: Adam Bernstein, MD, ScD
Last Review Date: 2022 Nov 9
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