What is the official name for vitamin K?

December 30, 2025 •

3 min read

The term "vitamin K" actually refers to a group of related compounds known as naphthoquinones, with each form having its own distinct official name. Unlike some other vitamins that are single molecules, vitamin K encompasses different structures, such as phylloquinone (K1) and menaquinone (K2), which have varying sources and functions in the body. This guide explores these scientific distinctions and their health implications.

Quick Summary

The official name for vitamin K varies depending on its specific form. Vitamin K1 is phylloquinone, found in plants, while vitamin K2 comprises menaquinones produced by gut bacteria and found in fermented foods. These fat-soluble compounds are critical for blood clotting and bone health.

Key Points

Phylloquinone is Vitamin K1: The official name for the plant-based form of vitamin K, found in high concentrations in leafy green vegetables and crucial for blood clotting.
Menaquinone is Vitamin K2: The collective official name for a group of vitamin K compounds (MK-4 to MK-13) produced by gut bacteria and found in fermented foods and animal products.
Essential for Blood Clotting: All forms of vitamin K are necessary for the synthesis of coagulation factors in the liver, which allows blood to clot properly.
Promotes Bone Health: Vitamin K is vital for activating proteins like osteocalcin, which helps bind calcium to the bone matrix, promoting strong and healthy bones.
Supports Cardiovascular Health: Vitamin K helps prevent vascular calcification by activating Matrix Gla Protein (MGP), which inhibits calcium buildup in blood vessel walls.
Deficiency Causes Bleeding: A lack of vitamin K can impair the body's ability to produce active clotting factors, leading to easy bruising and excessive bleeding.

Unveiling the Official Names for Vitamin K's Main Forms

While "vitamin K" is a common term, it's not a single substance but a family of chemically similar compounds. The two most biologically significant forms are vitamin K1 and vitamin K2, each with a different official designation and primary function. Understanding these distinctions is key to appreciating the vitamin's diverse roles in human health.

Phylloquinone: The Official Name for Vitamin K1

Phylloquinone is the scientific and official name for vitamin K1. This form is primarily synthesized by plants and is commonly found in green, leafy vegetables. Phylloquinone is essential for blood coagulation in humans, and a deficiency can impair clotting and increase bleeding risk.

Sources of Phylloquinone (Vitamin K1):

Leafy Greens: Spinach, kale, and collard greens are rich sources.
Vegetables: Broccoli, Brussels sprouts, and cabbage also contain K1.
Vegetable Oils: Soybean and canola oil provide phylloquinone.

Menaquinones: The Official Name for Vitamin K2

Menaquinone is the collective official name for vitamin K2 compounds. Menaquinones are mainly produced by bacteria and are found in fermented foods and certain animal products. They are classified as MK-4 through MK-13 based on their side chain length.

Types of Menaquinones (Vitamin K2):

MK-4: Found in animal products like meat, eggs, and liver.
MK-7: Primarily sourced from natto, a fermented soybean dish, with a longer half-life.
MK-8 and MK-9: Present in fermented dairy products such as cheese.

The Function of Vitamin K in the Body

Vitamin K acts as a co-enzyme in the carboxylation of specific proteins, a process vital for two major physiological functions.

Function in Blood Coagulation:

Vitamin K is crucial for the liver to synthesize blood clotting proteins, including factors II, VII, IX, and X.
It also aids in creating anticoagulant proteins like protein C and protein S.
Insufficient vitamin K leads to inactive clotting factors and potential bleeding disorders.

Function in Bone Metabolism and Cardiovascular Health:

Vitamin K is needed to activate osteocalcin, a protein that helps bind calcium to the bone matrix.
It activates Matrix Gla Protein (MGP), which prevents blood vessel calcification, supporting cardiovascular health.
Adequate vitamin K intake, especially K2, is linked to higher bone density and reduced fracture risk.

Comparison of Vitamin K1 (Phylloquinone) and Vitamin K2 (Menaquinone)


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Source	Green, leafy vegetables	Fermented foods and animal products
Main Role	Primarily involved in blood clotting	Supports bone and cardiovascular health
Production	Synthesized by plants	Produced by gut bacteria and derived from animal and fermented sources
Absorption Rate	Absorbed less efficiently than K2 from plants	Generally absorbed well from dietary sources
Half-Life	Shorter half-life in the bloodstream	Longer half-life, especially MK-7
Tissue Distribution	Concentrates in the liver	Distributed more widely to extrahepatic tissues like bones and blood vessels

Potential Issues: Deficiency and Interactions

Vitamin K deficiency is rare in healthy adults but can occur with malabsorption disorders, liver disease, or antibiotic use. Symptoms include excessive bleeding or bruising. Newborns receive a vitamin K shot to prevent life-threatening deficiency.

Dietary vitamin K levels are critical for those taking warfarin. Warfarin interferes with the vitamin K cycle, so inconsistent intake of vitamin K-rich foods can affect the medication's effectiveness and requires careful monitoring. For more information, see this National Institutes of Health (NIH) article.

Conclusion: The Different Faces of Vitamin K

The official name for vitamin K depends on the specific form: phylloquinone for plant-based K1, essential for blood clotting, and menaquinone for K2, important for bone and cardiovascular health. A balanced diet with leafy greens and fermented foods ensures intake of these vital compounds.

Frequently Asked Questions

For vitamin K1 (phylloquinone), green leafy vegetables are the best sources. Spinach, kale, and collard greens are particularly high in this form of the vitamin.

Both vitamin K1 and K2 are important for different reasons. K1 is critical for blood clotting, while K2 is more effective at supporting bone and cardiovascular health. A balanced diet containing sources of both is ideal.

Mild vitamin K deficiency is often treated with oral supplementation or dietary changes. In more severe cases or for newborns, parenteral administration (injection) of phytonadione (vitamin K1) may be used.

There is no known toxicity associated with high doses of dietary vitamin K1 or K2. However, individuals on blood-thinning medication like warfarin must maintain a consistent intake to avoid interfering with their treatment.

Newborns are at risk for vitamin K deficiency bleeding (VKDB), a serious condition caused by low vitamin K levels. A prophylactic vitamin K injection is routinely given at birth to prevent this.

Menadione is a synthetic form of vitamin K (K3). It is not used in dietary supplements or fortified foods due to its potential for toxicity in humans, and is generally used for animal feed or research.

Warfarin works by inhibiting the enzyme that activates vitamin K. An increase in dietary vitamin K can counteract warfarin's effect, making the blood thinner less effective. A consistent intake is therefore essential for individuals on this medication.