Vitamin K is a fat-soluble vitamin, which is primarily needed for the production of certain proteins that are important for blood clotting. This vitamin derives its name from the Danish word koagulation, which means blood clotting. Of the thirteen proteins needed for the process of blood clotting, vitamin K plays a key role in the synthesis of four. Individuals who are on anticoagulants or blood thinners need to be careful about maintaining their vitamin K levels. 

Additionally, this vitamin also plays a vital role as a supplement in the treatment of diseases such as osteoporosis (weakening of bones), vascular calcification (calcium deposition in the blood vessels), osteoarthritis, and cancer.

  1. Sources of vitamin K
  2. Benefits of vitamin K
  3. Vitamin K dosage
  4. Vitamin K deficiency
  5. Side effects of vitamin K

Vitamin K can be found in two forms in various food sources. These forms are vitamin K1 and vitamin K2. Vitamin K1 (phylloquinone or phytomenadione) is commonly found in plant-based food sources such as dark green leafy vegetables, whereas Vitamin K2 (menaquinone) is more commonly found in animal food sources and fermented dairy products.

Vitamin K3 is the third form, a synthetic one, and is called menadione. It has been banned by the Food and Drug Administration of the USA due to its high potential for toxicity.

Animal sources of Vitamin K

Some common and naturally-occurring animal sources of vitamin K are egg yolk, mayonnaise, chicken liver, chicken breast, yoghurt, margarine, ground beef, hard cheese such as gouda, soft cheese such as blue cheese, salami, butter, and fermented milk (kefir).

Plant sources of Vitamin K

Vitamin K is mainly found in cooked dark green vegetables such as spinach, broccoli, coleslaw, and asparagus. It is also found in foods such as soybean oil, grapes, plums, kidney beans, and certain traditional fermented foods such as Natto (fermented soy) and Sauerkraut.

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Vitamin K for the skin

Vitamin K helps to heal bruises faster. It has been seen that the application of vitamin K cream on bruises caused by laser treatment reduces the severity of bruises. This healing effect of vitamin K cream is more pronounced in the initial days of application.

Studies have shown that vitamin K also helps to fight dark circles that tend to form under the eyes with ageing and also assists to reduce and even reverse the formation of facial wrinkles.

(Read more: Skincare routine for a flawless skin)

Vitamin K for bones

Vitamin K is essential for bone health and helps to prevent osteoporosis. Osteoporosis is an extremely common condition in the elderly population and is one of the leading causes of fractures globally. It is estimated that one in three women and one in five men above the age of 50 years experience a fracture due to osteoporosis. In a study including osteoporotic people, it was noted that those who were given vitamin K supplements along with calcium maintained their bone density better as compared to the others who were given only calcium. 

Researchers have shown that a low level of circulating vitamin K is associated with low bone density. Studies have also indicated that high vitamin K consumption significantly reduces the risk of hip fracture in men and women. Additionally, it helps increase bone mineral density in women.

It is recommended to include at least one serving of a dark green leafy vegetable, such as lettuce, every day in the diet to obtain adequate vitamin K.

(Read more: Osteoporosis diet)

Vitamin K for the heart

Vascular calcification is a condition where plaque builds up within blood vessels. Calcification of the blood vessels is one of the most important risk factors for cardiovascular diseases (heart diseases). Studies have shown that a diet rich in vitamin K may be able to reverse calcification in the arteries following treatment that prevents the formation of blood clots in the heart. It should be noted that the intake of both vitamin K1 and vitamin K2 is required for complete protection of the blood vessels from calcification. Also, vitamin K2 is more efficient in protecting the blood vessels against calcification and reversing calcification in its arteries than vitamin K1.

Research studies also indicate that intake of vitamin K along with vitamin D supplements helps to better maintain the elastic properties of blood vessels in postmenopausal women compared to women who only take vitamin D supplements.

(Read more: Menopause symptoms)

Vitamin K for arthritis

Osteoarthritis is a debilitating condition that affects the joints of your body by damaging the surrounding cartilages and narrowing the space between two bones in a joint. This leads to stiffness and pain. Recent research has shown that vitamin K may play an important role in preventing osteoarthritis in people with vitamin K deficiency.

Rheumatoid arthritis is an autoimmune disease where the body's immune system attacks the joints leading to pain and inflammation (swelling). Studies have shown that vitamin K2 supplements reduce the inflammation caused by rheumatoid arthritis.

(Read more: Arthritis types)

Vitamin K for newborns

The World Health Organization (WHO) recommends that all newborn babies be given a vitamin K supplement in the form of an intramuscular injection after the first hour of birth. Vitamin K is essential to prevent bleeding in preterm infants, infants with birth trauma, and infants who were exposed to certain medications in the mother's womb that interfere with vitamin K absorption. Vitamin K supplementation in infants is also essential because most babies do not receive adequate vitamin K from their mothers in the womb or when they are breastfeeding. Internal bleeding due to vitamin K deficiency may result in brain damage and even death. Vitamin K supplementation for newborns is especially important if the mothers have taken medication for epilepsy, blood clots, or tuberculosis during their pregnancy.

Other benefits of Vitamin K

Apart from the abovementioned health benefits, here are some other benefits of vitamin K:

  • Prevents Cancer
    Vitamin K may help to prevent certain kinds of cancer. Vitamin K has shown to be beneficial to people with liver cancer and liver cirrhosis.
  • Improves Insulin sensitivity
    Vitamin K is known to improve insulin sensitivity and may be helpful for people with diabetes and prediabetes.

(Read more: Insulin resistance causes)

There is no Recommended Dietary Allowance (RDA) for vitamin K, therefore, the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies has established an Adequate Intake (AI) level. The required vitamin K levels are stated in micrograms (mcg).

  • AI for infants below 6 months is 2.0 mcg. It is assumed that these infants are healthy, with average weight and are breastfed.
  • Infants from the age of 7 months to 12 months require 2.5 mcg.
  • Children in the age group of 1 to 3 years are recommended an AI of 30 mcg, and those between 4 to 8 years require 55 mcg of vitamin K.
  • Adolescents between 9 to 13 years of age require 60 mcg, while teens between 14 to 18 years need 75 mcg of vitamin K.
  • Males above 19 years require an AI of 120 mcg, while females require 90 mcg (including pregnant and lactating women).

A person is said to be deficient in vitamin K only when their body takes longer than the normal time to form a blood clot in case of an injury. On an average, human body takes somewhere between 10 and 14 seconds to form a blood clot on an injury site.

Late clotting in case of vitamin K deficiency occurs because the prothrombin activity of the blood (i.e. the protective function of the blood to clot) is significantly reduced due to the deficiency of vitamin K. Therefore, excess or abnormal bleeding is often the first and only sign of vitamin K deficiency. However, these signs do no manifest or show up clearly except in severe cases. Thus, vitamin K deficiency is not diagnosed easily.

A deficiency of vitamin K may occur in newborns because of low levels of this vitamin in breast milk and during birth. Deficiency of vitamin K is rare in healthy adults. Individuals who have severe digestive disorders and have been taking antibiotics for long may be at a risk of developing vitamin K deficiency.

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An upper limit for vitamin K level in the body has not been established because it has a very low possibility of causing toxicity. A study published by the Food and Nutrition Board notes that no harmful effects due to consumption of vitamin K from food sources or supplements have been reported in humans or in animals.

Medicines / Products that contain Vitamin K


  1. A. J. van Ballegooijen, J. W. Beulens. The Role of Vitamin K Status in Cardiovascular Health: Evidence from Observational and Clinical Studies . Curr Nutr Rep. 2017; 6(3): 197–205. PMID: 28944098
  2. Gerry Kurt Schwalfenberg. Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health . J Nutr Metab. 2017; 2017: 6254836. PMID: 28698808
  3. Health Harvard Publishing. Harvard Medical School [Internet]. Vitamin K. Harvard University, Cambridge, Massachusetts.
  4. Neha S. Shah et al. The effects of topical vitamin K on bruising after laser treatment. Journal of American Academy of Dermatology
  5. Fatemeh Ahmadraji, Mohammad Ali Shatalebi. Evaluation of the clinical efficacy and safety of an eye counter pad containing caffeine and vitamin K in emulsified Emu oil base . Adv Biomed Res. 2015; 4: 10. PMID: 25625116
  6. James J DiNicolantonio et al. The health benefits of vitamin K . Open Heart. 2015; 2(1): e000300. PMID: 26468402
  7. Braam LA et al. Beneficial effects of vitamins D and K on the elastic properties of the vessel wall in postmenopausal women: a follow-up study. Thromb Haemost. 2004 Feb;91(2):373-80. PMID: 14961167
  8. World Health Organization [Internet]. Geneva (SUI): World Health Organization; Newborn Health.
  9. healthdirect Australia. Vitamin K at birth. Australian government: Department of Health
  10. National Institutes of Health; Office of Dietary Supplements. [Internet]. U.S. Department of Health & Human Services; Vitamin K.
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