Which of the Following Non-Food Sources Provide Vitamin K?

January 5, 2026 •

4 min read

While most people associate vitamin K with leafy green vegetables, a significant portion of this vital nutrient is produced by your own gut bacteria. For individuals who don't get enough from diet alone, non-food sources like supplements and medical injections ensure adequate levels for proper blood clotting and bone health. Understanding these alternative sources is essential for maintaining optimal health.

Quick Summary

Several non-food sources supply vitamin K, including endogenous synthesis by intestinal bacteria and external provision through dietary supplements and medical injections, particularly for newborns.

Key Points

Intestinal Bacteria: Your gut flora naturally produces menaquinones (vitamin K2), which contributes to your total vitamin K levels.
Dietary Supplements: Oral supplements containing vitamin K1 (phytonadione) or vitamin K2 (menaquinone-4, MK-7) are a safe and effective non-food source for addressing deficiencies.
Newborn Injections: All newborns are given a vitamin K injection at birth to prevent a life-threatening bleeding disorder (VKDB) because their vitamin K stores are dangerously low.
Synthetic Forms: While synthetic vitamin K1 (phytonadione) is used in medicine, the analog menadione (K3) is toxic to humans and is banned from supplements.
Source Variations: The reliability of each non-food source varies, with medical injections being the most effective for newborns and gut production being inconsistent for some adults.

Intestinal Bacteria: The Endogenous Factory

Your body has a fascinating internal mechanism for producing vitamin K. The bacteria that colonize your lower intestinal tract, often referred to as gut flora, are responsible for synthesizing a form of vitamin K known as menaquinones (vitamin K2). While a diverse population of gut bacteria exists, certain types, including members of the Escherichia, Bacteroides, and Eubacterium genera, are known producers of menaquinones. This endogenous production contributes to your total vitamin K status, though its sufficiency varies widely among individuals.

The Role of Gut Flora

The menaquinones produced by gut bacteria play a crucial role in various biological processes, including maintaining proper blood coagulation and contributing to bone health. However, factors like antibiotic use or gastrointestinal disorders can disrupt the bacterial population, potentially reducing the body's natural vitamin K production. For newborns, this endogenous production is initially insufficient because their digestive tract is sterile at birth. This is a primary reason why medical intervention is required.

Dietary Supplements: A Targeted Approach

For those with dietary deficiencies or specific health needs, oral dietary supplements serve as a direct, non-food source of vitamin K. Supplements typically contain either vitamin K1 (phylloquinone) or vitamin K2 (menaquinone) in various formulations. They are available as standalone nutrients or combined with other complementary vitamins and minerals, most commonly vitamin D and calcium, due to their synergistic roles in bone health.

Forms of Vitamin K in Supplements

Vitamin K1 (Phylloquinone/Phytonadione): The form found in plants and available in supplements. Phytonadione is a synthetic version of K1 often used in dietary supplements and medication.
Vitamin K2 (Menaquinone-4 and Menaquinone-7): The bacterial form of vitamin K. MK-7 is considered highly bioavailable and has a longer half-life than MK-4 or K1.
Vitamin K3 (Menadione): A synthetic form that has been shown to cause toxicity in humans and is therefore no longer used in human supplements.

Medical Prophylaxis: The Newborn Injection

One of the most critical non-food applications of vitamin K is the prophylactic injection given to newborns. All babies are born with very low levels of vitamin K, which puts them at risk for a life-threatening condition called Vitamin K Deficiency Bleeding (VKDB). This is because vitamin K does not cross the placenta easily, and the newborn's gut is not yet fully colonized with vitamin K-producing bacteria.

Why Injections Are Recommended

The single intramuscular injection of vitamin K at birth is the most effective way to prevent VKDB, dramatically reducing the risk from approximately 1 in 100 to as low as 1 in 10,000. Oral alternatives are less effective because absorption can be inconsistent, especially in sick or exclusively breastfed infants. The injection provides a long-lasting reservoir of the vitamin, offering crucial protection during the first several weeks of life.

Comparison of Non-Food Vitamin K Sources


Feature	Intestinal Bacteria (Endogenous)	Dietary Supplements (Exogenous)	Medical Injections (Exogenous)
Primary Form	Menaquinones (K2)	Phylloquinone (K1) and Menaquinones (K2)	Phytonadione (K1)
Target User	Healthy individuals (natural contribution)	Anyone needing targeted supplementation	All newborns at birth
Delivery Method	Synthesized by gut flora	Oral capsules or liquid	Intramuscular injection
Reliability	Variable, influenced by diet and health	High, with controlled dosages	Very high, considered gold standard
Purpose	Daily physiological maintenance	Correcting deficiency, supporting bone health	Preventing newborn bleeding (VKDB)
Known Risks	Disruption by antibiotics or disease	Mild, allergic reaction possible	Transient pain, swelling at injection site

The Role of Synthetic vs. Natural K

For human consumption, only the natural forms, vitamin K1 (phylloquinone) and vitamin K2 (menaquinone), are used in supplements and medicines. The synthetic analog menadione (K3) is banned from human use in many countries due to its potential for toxicity, including causing hemolytic anemia and liver damage. While synthetic versions of natural forms (like phytonadione, a synthetic K1) are safe and effective, menadione is a distinctly different and harmful compound. The body can convert some K1 into K2 (MK-4), and gut bacteria synthesize various menaquinones (MK-6 to MK-11). Supplements often use MK-7, derived from fermented soybeans, for its bioavailability.

Conclusion

Vitamin K, a crucial nutrient for blood clotting and bone health, is not solely derived from food. The human body receives vitamin K from several non-food sources, including endogenous synthesis by intestinal bacteria, exogenous intake via dietary supplements, and medical injections. While a healthy gut microbiome contributes to the body's menaquinone supply, supplementation and medical prophylaxis are essential for correcting deficiencies and protecting vulnerable populations like newborns. The variety of non-food vitamin K sources ensures that even when dietary intake is low, the body has mechanisms to maintain adequate levels, highlighting the nutrient's importance to overall health. For most adults with a balanced diet, gut bacteria suffice, but supplements offer a reliable boost, and the medical community relies on targeted injections for critical needs.

Visit the NIH Office of Dietary Supplements for more information

Frequently Asked Questions

Gut bacteria primarily synthesize menaquinones, which are also known as vitamin K2. Specific bacterial species, such as E. coli and Bacteroides, are known to produce menaquinones in the large intestine.

Newborns are born with very low levels of vitamin K, putting them at high risk for Vitamin K Deficiency Bleeding (VKDB). A single, highly effective injection at birth is the standard prophylaxis to prevent this dangerous bleeding.

Yes, vitamin K1 (phylloquinone/phytonadione) and vitamin K2 (menaquinones) supplements are generally considered safe for adults. Unlike the toxic synthetic form K3 (menadione), K1 and K2 have a low potential for toxicity.

No, while some research suggests potential connections between sunlight and vitamin K2 synthesis, it is not a reliable source. Excessive sunlight is harmful, and the effect on vitamin K production is not well-established.

Yes, prolonged use of antibiotics can destroy the vitamin K-producing bacteria in your gut. This may reduce the amount of vitamin K available to your body, though supplementation is typically only necessary for long-term use.

Menaquinone-7 (MK-7), a form of vitamin K2 often found in supplements, has been shown to have a longer half-life and potentially better absorption than other forms like vitamin K1.

Vitamin K3, or menadione, is a synthetic form of vitamin K that has been shown to cause liver damage and other toxic effects in humans. For safety reasons, it is no longer used in human supplements and is primarily for animal feed.