What is the cause of vitamin K deficiency?

October 15, 2025 •

4 min read

Although vitamin K deficiency is rare in healthy adults, it is a significant concern for certain at-risk populations, particularly newborns. Understanding what is the cause of vitamin K deficiency is crucial for preventing complications related to blood clotting and bone health.

Quick Summary

An inadequate level of vitamin K stems from poor dietary intake, fat malabsorption disorders, liver disease, antibiotic use, and specific conditions in newborns. Identification of the underlying reason is key to effective management and preventing bleeding complications.

Key Points

Newborn Vulnerability: Newborns are particularly susceptible to vitamin K deficiency due to limited placental transfer, low vitamin levels in breast milk, and a sterile gut at birth.
Fat Malabsorption: Since vitamin K is fat-soluble, conditions like cystic fibrosis, celiac disease, and chronic diarrhea can impair its absorption.
Liver Disease: The liver's role in processing vitamin K means conditions like cirrhosis can lead to impaired utilization and synthesis of clotting factors.
Medication Effects: Long-term use of certain broad-spectrum antibiotics can reduce gut bacteria production of vitamin K, while anticoagulants like warfarin interfere with its function.
Dietary Intake and Fat: An extremely low-fat diet or poor nutrition can directly cause a deficiency, as some fat is needed for proper vitamin K absorption.
Treatment Approach: Addressing the deficiency requires treating the underlying cause, whether it's dietary, medicinal, or related to a medical condition.

Vitamin K is a fat-soluble vitamin essential for producing vital proteins involved in blood clotting and bone metabolism. While many people associate it only with green vegetables, vitamin K is actually a family of compounds. A deficit in this vitamin can have serious consequences, ranging from easy bruising to life-threatening bleeding. Identifying the underlying cause is the first step toward successful management and prevention.

Dietary Factors

One of the most straightforward explanations for a deficiency is inadequate intake of vitamin K-rich foods. While dietary deficiency is uncommon in healthy adults with a balanced diet, it is possible under certain circumstances.

Low Vitamin K Intake

Poor dietary habits that neglect foods like leafy green vegetables, certain vegetable oils, and fermented foods can lead to low vitamin K levels over time. A very low-fat diet can also impair absorption, since vitamin K is fat-soluble and requires fat to be absorbed effectively. In older adults or those with limited food access due to illness or poverty, malnutrition is a contributing factor to deficiency.

Vitamin K Deficiency in Newborns

Newborn infants are a particularly high-risk group for vitamin K deficiency bleeding (VKDB). Several factors contribute to this vulnerability:

Limited placental transfer: Only a small amount of vitamin K is passed from the mother to the fetus during pregnancy.
Low levels in breast milk: Breast milk contains very little vitamin K, making exclusively breastfed babies more susceptible.
Sterile gut at birth: A newborn's intestines do not yet have the bacteria that synthesize vitamin K2.
Immature liver: The neonatal liver is not fully developed and struggles to process the vitamin efficiently.

For these reasons, newborns are routinely given a vitamin K shot shortly after birth to prevent serious bleeding.

Medical Conditions Affecting Absorption and Metabolism

For many, the root cause of a vitamin K deficiency is not a lack of intake but a problem with absorption or utilization. These are often referred to as malabsorption disorders.

Fat Malabsorption Syndromes

Since vitamin K is fat-soluble, any condition that prevents the body from absorbing fat can lead to a deficiency. This occurs because the body cannot effectively absorb the vitamin, even with adequate dietary intake. Conditions that can cause fat malabsorption include:

Cystic fibrosis: This genetic disorder damages the lungs and digestive system, impairing nutrient absorption.
Celiac disease: An autoimmune disorder where consuming gluten damages the small intestine, leading to malabsorption.
Chronic diarrhea and inflammatory bowel disease (IBD): These conditions can disrupt the intestinal lining, affecting absorption.
Short bowel syndrome: Results from surgical removal of a large portion of the small intestine, reducing the surface area for absorption.

Liver and Biliary Tract Disease

The liver plays a central role in vitamin K metabolism and the production of blood-clotting proteins. Therefore, impaired liver function can significantly increase the risk of deficiency. Key issues include:

Liver cirrhosis and other parenchymal diseases: These conditions interfere with the liver's ability to utilize vitamin K to synthesize clotting factors.
Biliary obstruction: The flow of bile is crucial for fat absorption. A blockage in the bile ducts prevents the absorption of fat-soluble vitamins like vitamin K, leading to deficiency.

Medications and Vitamin K Levels

Several types of medications can interfere with vitamin K metabolism or absorption, sometimes leading to a deficiency.

Anticoagulants (Blood Thinners)

Drugs like warfarin are antagonists of vitamin K, meaning they actively block the vitamin's function. Patients on these medications must carefully monitor their vitamin K intake to maintain a consistent blood-clotting response, though this is a therapeutic intervention and not a true deficiency.

Antibiotics

Long-term use of broad-spectrum antibiotics can disrupt the gut bacteria responsible for producing vitamin K2. This is not a primary concern for short courses of antibiotics but can be relevant during extended treatment or in individuals with limited dietary intake. Certain cephalosporin antibiotics may have a more direct inhibitory effect on vitamin K's function.

Other Medications

Other drug classes can interfere with absorption or metabolism, including:

Cholestyramine: Used for high cholesterol, it binds to bile acids, which are necessary for fat and fat-soluble vitamin absorption.
Anti-seizure drugs: Some anticonvulsants, like phenytoin, can interfere with vitamin K metabolism.

Comparison of Vitamin K1 and K2 Sources

Vitamin K exists in two primary forms: K1 (phylloquinone) and K2 (menaquinone). Understanding the sources of each can help address dietary deficiencies.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Sources	Plant-based foods, especially green leafy vegetables.	Animal products, fermented foods, and gut bacteria.
Key Food Examples	Kale, spinach, broccoli, collard greens, lettuce, vegetable oils.	Nattō (fermented soy), Gouda cheese, blue cheese, egg yolks, some meat.
Absorption	Primarily absorbed in the small intestine.	Absorbed more readily than K1 and has a longer half-life.
Function	Primarily involved in blood coagulation.	Plays a crucial role in bone health and cardiovascular health.

Conclusion

While a deficiency in vitamin K is uncommon in otherwise healthy adults, a number of conditions can put individuals at risk. The primary causes include inadequate dietary intake, conditions that cause fat malabsorption, and certain medications. Newborns are an especially vulnerable group. Correcting a deficiency often requires treating the underlying medical condition and may involve dietary adjustments and supplementation under medical supervision. Given vitamin K's critical role in blood clotting and bone health, identifying and addressing the specific cause is a key component of nutritional management.

For more in-depth information on vitamin K and its functions, refer to the National Institutes of Health (NIH) Office of Dietary Supplements website [https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/].

Frequently Asked Questions

Common signs of vitamin K deficiency include easy bruising, excessive bleeding from wounds or gums, heavy menstrual periods, and blood appearing in the urine or stool.

Newborns are susceptible because only a small amount of vitamin K crosses the placenta, their gut bacteria haven't started producing it yet, and breast milk is a poor source. For this reason, a vitamin K shot is recommended at birth.

Yes, prolonged use of certain antibiotics, especially broad-spectrum ones, can destroy the gut bacteria that produce vitamin K2, potentially leading to a deficiency, particularly if dietary intake is also low.

Extremely low-fat diets increase the risk because vitamin K is fat-soluble and requires some fat for absorption. A diet consistently low in leafy green vegetables and other rich sources also contributes to dietary deficiency.

Treatment involves addressing the underlying cause. It can include dietary changes to increase intake, but often requires oral supplements or injections of vitamin K, especially in cases of malabsorption or severe deficiency.

Medical conditions that cause fat malabsorption are the main culprits. These include liver disease (like cirrhosis), biliary tract obstruction, cystic fibrosis, celiac disease, and chronic inflammatory bowel disease.

Yes, severe liver disease, such as cirrhosis, significantly increases the risk of vitamin K deficiency. The liver is where vitamin K is used to produce key blood clotting factors, and liver damage impairs this process.