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Vitamin K


Vitamin K is a fat soluble vitamin that is needed for normal blood clotting. It is also involved in the making of bone proteins.



Good food sources include:

  • green leafy vegetables such as kale, spinach, salad greens, cabbage, broccoli and Brussel sprouts,
  • certain plant oils such as soybean and canola oils, and margarines and salad dressings made from them, and
  • some fermented cheeses.


Bacteria in your gastrointestinal tract also make vitamin K.



The amount of vitamin K that is likely to be adequate depends on your age and gender. You may need to moderate your vitamin K intake if you are taking blood thinning drugs such as anticoagulants. The Adequate Intake (AI) below reflects the amount estimated to be adequate for most people.


  AI (mg/day)                                                                                                     
0-6 months 2
7-12 months 2.5
1-3 years 25
4-8 years 35
9-13 years 45
Adolescents (14-18 years) 55
Men (19+ years) 70
Women (19+ years) 60



Vitamin K deficiency from inadequate intake from food is rare, however, it can occur if your body is unable to properly absorb the vitamin from the intestinal tract, such as if you suffer from a fat malabsorption condition. It can also occur if you have been taking antibiotics for a long time, as antibiotics can destroy vitamin K producing bacteria.


Symptoms of deficiency may include:

  • increased clotting time,
  • bruising, and
  • bleeding.



There are no known side effects of having a high intake of vitamin K from food or supplements. However, if you are taking blood thinning drugs you may need to limit your intake of vitamin K as vitamin K can affect how these drugs work. If this affects you, seek advice from your health care professional.



The content displayed on this webpage is intended for informational purposes and is a guide only. It does not replace or substitute for professional medical advice, diagnosis or treatment.

Information contained on this webpage must be discussed with an appropriate healthcare professional before making any decisions or taking any action based on the content of this webpage.



Harvard School of Public Health


Medline Plus Medical Encyclopaedia


National Health and Medical Research Council


Stewart R., Griffith Handbook of Clinical Nutrition and Dietetics (2nd edition)