Vitamin K – Benefits, Toxicity, and More

Lettuce contains Vitamin K

Introduction to Vitamin K

Commonly known as the “clotting vitamin’, Vitamin K functions as a coenzyme during the synthesis of the biologically active form of a number of proteins involved in blood coagulation and bone metabolism. It is fat-soluble and is eliminated in feces or urine after being rapidly broken down. Unlike other fat-soluble vitamins, it rarely reaches toxic levels in the body even when taken in large quantities.

What are Vitamin K types?

It has two forms; the most common type is phylloquinone (Vitamin K1), which can be found in green leafy vegetables like spinach, kale, and collard greens. Menaquinones (Vitamin K2), the other type, can be found in fermented foods and some animal products. Menaquinones can also be made in the body by bacteria.

Food Sources

There is an abundance of vitamin K in food, and a variety of foods that contain it, namely;

  • Natto (fermented soybeans)
  • Meat,
  • Cheese, and eggs

Phylloquinones are found in;

  • Green leafy vegetables like collard and turnip greens, kale, spinach, broccoli, Brussels sprouts, cabbage, and lettuce.
  • Soybean
  • Canola oil
What does Vitamin K do in the body?

It plays a key role in the production of various proteins, which are essential for the formation of bones and the clotting of blood. Blood clotting is directly mediated by prothrombin protein, a vitamin K-dependent factor. Moreover, it is required by the hormone osteocalcin, which makes healthy bone tissue.

Vitamin K2 and Vitamin D3 benefits, together

Vitamin D3 and vitamin K2, synergistically ensure that calcium is absorbed easily and reaches the bones while preventing arterial calcification, helping to keep your heart and bones healthy. Separately, K2 regulates normal blood clotting, whilst D3 supports a healthy immune system and supports muscle function.


What are the benefits, Vitamin K manifests for severe conditions?
  • Bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease): Giving newborns vitamin K1 by mouth or as a shot into the muscle helps prevent bleeding. Shots seem to work the best, but can only be given by a healthcare provider.
  • Weak and brittle bones (osteoporosis): Taking vitamins K1 & 2 by mouth seems to improve bone strength and reduce the risk of fractures in people with weak bones. But it doesn’t seem to benefit those who still have strong bones.
  • Low levels of the blood clotting protein prothrombin (hypoprothrombinemia): Taking vitamin K1 by mouth or by IV can prevent and treat bleeding problems in people with low levels of prothrombin. Note that IV products can only be given by a healthcare provider.
  • A rare, inherited bleeding disorder (Vitamin K-dependent clotting factors deficiency or VKCFD): Taking vitamin K by mouth or by IV can help prevent bleeding in people with VKCFD. However, IV products can only be given by a healthcare provider.
  • Reversing the blood thinning effects of warfarin: Taking vitamin K1 by mouth or by IV can reverse the effects of warfarin, a blood thinner. IV products can only be given by a healthcare provider.


Recommended Dietary Intake
0-6 months2 mcg2 mcg  
7-11 months2.5 mcg2.5 mcg  
1-3 years30 mcg30  mcg  
4-8 years55 mcg55 mcg  
9-13 years60 mcg60 mcg  
14-18 years75 mcg70 mcg75 mcg75 mcg
19+ years120 mcg90 mcg90 mcg90 mcg

*These doses are for ideal conditions, consult your physician before deciding on a dose for yourself*

Deficiency Symptoms

Adults rarely are deficient in it, but it can happen if they take antibiotics, which block its metabolism, low intake of foods that contain vitamin K, or have conditions that make it hard for nutrients to be absorbed.

Vitamin K symptoms of deficiency are;

  • Bleeding
  • Hemorrhaging
  • Osteopenia or osteoporosis
  • A longer time for blood to clot or a prolonged prothrombin time (as measured in a physician’s office)
Vitamin K and bruising

Bruising could be caused by a lack of vitamin K. It is a fat-soluble nutrient that is necessary for blood clotting and contributes to the strengthening of capillary walls, making them less likely to break. Since the body needs fat to use vitamin K, people who can’t absorb fat or who take certain drugs that make it hard for the body to absorb fat may not have enough of it.


Treatment for Deficiency

A post-partum injection of vitamin K to newborns is recommended to prevent brain bleeding.

It is typically taken orally or injected under the skin in patients with its deficiency. If a medication is a cause of deficiency, the dosage of the medication is reduced or Vitamin K is added.

Toxicity Symptoms

Upper limits for it are not established because of its low potential for toxicity. In this report, it is stated that “no adverse effects associated with vitamin K consumption from food or supplements have been reported in humans or animals.”


A vitamin K supplement may be beneficial to people who experience a lack of appetite while taking long-term antibiotics or drugs such as warfarin, because they may be more susceptible to its deficiency.

it is best absorbed when eaten in foods high in fat because it is fat-soluble. So, dress your favorite salad of leafy greens with olive oil or diced avocado!


About the Author

Saleh Siddiqui

Doctor of Pharmacy (Pharm. D) and Content Author at KeepUpFitness.

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