What Does It Mean If My Vitamin K Is Low?

November 27, 2025 •

3 min read

According to the Centers for Disease Control and Prevention, newborns who do not receive a vitamin K shot at birth are at a significantly higher risk for developing vitamin K deficiency bleeding (VKDB), a potentially life-threatening condition. For both infants and adults, a low vitamin K level can signal serious health problems related to blood clotting, bone density, and other physiological processes.

Quick Summary

A low vitamin K level can lead to bleeding issues, easy bruising, and poor bone health. It is often caused by malabsorption, certain medications, or dietary deficiency. This article explores the signs, causes, and diagnostic methods for vitamin K deficiency, detailing the critical functions of this fat-soluble vitamin in the body.

Key Points

Bleeding and Bruising: A low vitamin K level significantly impairs blood clotting, leading to symptoms like easy bruising and excessive bleeding from wounds, gums, or the nose.
Compromised Bone Health: Vitamin K is crucial for activating proteins that bind calcium to bones. A deficiency can result in decreased bone density, contributing to conditions like osteoporosis and increasing fracture risk.
High-Risk Groups: Certain populations are at a higher risk, including newborns (who receive a prophylactic shot at birth), individuals with fat malabsorption conditions, those with liver disease, and people on specific medications like warfarin or long-term antibiotics.
Malabsorption is a Key Cause: In adults, deficiency is most often a secondary issue caused by conditions that prevent proper fat absorption in the intestines, such as cystic fibrosis, celiac disease, or Crohn's disease.
Diagnosis Through Blood Tests: Doctors diagnose a deficiency with a Prothrombin Time (PT) blood test, which measures how long blood takes to clot. An elevated PT/INR can confirm the issue.
Treatment is Effective: Treatment typically involves oral or injectable vitamin K supplementation to restore clotting function and support bone health, with rapid improvement in most cases.
Dietary Intake is Important: While severe dietary deficiency is rare in healthy adults, consuming vitamin K-rich foods like leafy greens, broccoli, and fermented products is essential for maintaining adequate levels.

The Crucial Role of Vitamin K

Vitamin K is a fat-soluble vitamin essential for producing specific proteins necessary for blood clotting and bone health. The two main types are Vitamin K1 (phylloquinone) from plants and Vitamin K2 (menaquinone) from gut bacteria, animal, and fermented foods.

Low vitamin K levels compromise the body's ability to clot blood effectively and can lead to long-term issues like weakened bones.

Signs and Symptoms of Low Vitamin K

Signs of low vitamin K can vary, with some being more apparent than others:

Excessive bleeding: Difficult to stop bleeding from minor injuries or procedures is a common symptom.
Easy bruising: Bruises appearing without significant impact.
Internal bleeding: Indicated by blood in the stool or urine.
Heavy menstrual bleeding: Unusually heavy periods in women.
Mucosal bleeding: Bleeding from the gums or nose.
Newborn issues: Bleeding from the umbilical cord or, in severe cases, brain bleeds.

What Causes Vitamin K to Be Low?

A low vitamin K level in adults is typically due to underlying health conditions or medications rather than just diet, although a very low-fat diet can contribute.

Medical conditions

Fat malabsorption: Conditions like cystic fibrosis, celiac disease, and liver disease hinder fat absorption, which is needed for vitamin K absorption.
Liver disease: Impairs the production of vitamin K-dependent clotting factors.
Other conditions: Chronic illness, alcoholism, and long-term IV feeding increase risk.

Medications

Anticoagulants: Drugs like warfarin interfere with vitamin K's function.
Antibiotics: Long-term use can reduce gut bacteria producing Vitamin K2.

Risk factors in newborns

Limited transfer: Only a small amount of vitamin K is transferred from mother to baby during pregnancy.
Low breast milk content: Breast milk contains low levels of vitamin K.

Diagnosing and Treating a Deficiency

Diagnosing low vitamin K involves blood tests to check clotting time.

Diagnostic tests

PT and INR: Standard tests measuring blood clotting speed; prolonged results suggest deficiency.
PIVKA-II: A more sensitive test for detecting subtle deficiency.

Treatment options

Treatment focuses on restoring vitamin K levels.

Oral supplements: Common for replenishing vitamin K.
Injections: Used for severe bleeding to quickly administer vitamin K.
Dietary changes: Increasing intake of vitamin K-rich foods may be recommended.

Comparison of Vitamin K Forms (K1 vs. K2)


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Source	Leafy green vegetables and vegetable oils.	Fermented foods, organ meats, and cheeses.
Primary Function	Primarily involved in liver-based blood clotting.	More active in extra-hepatic tissues like bones and blood vessels.
Production	Directly consumed from plants.	Produced by gut bacteria and found in animal/fermented foods.
Absorption	May require dietary fat for optimal absorption from plant sources.	Generally absorbed more readily and may have a longer half-life.

Conclusion

Understanding the implications of low vitamin K is crucial due to its role in blood clotting and bone health. While uncommon in healthy adults, it is a significant risk for newborns and individuals with malabsorption disorders, liver disease, or those on certain medications. Prompt diagnosis via blood tests like PT/INR and appropriate treatment, often involving supplementation and dietary adjustments, are essential to prevent serious complications, especially life-threatening bleeding. Maintaining a diet rich in vitamin K and being aware of personal risk factors are key preventive measures. Consulting a healthcare professional or registered dietitian is recommended for diagnosis and personalized guidance.

Frequently Asked Questions

The main role of vitamin K is to help the body produce the proteins needed for blood clotting (coagulation). It is also important for maintaining healthy bones by activating proteins that help bind calcium to the bone structure.

A low vitamin K level is diagnosed with a blood test called a prothrombin time (PT) or international normalized ratio (INR). This test measures how long it takes for your blood to clot. A prolonged PT or elevated INR can indicate a deficiency.

Newborns are at risk because they have very little vitamin K stored in their body at birth, their gut lacks the bacteria to produce it, and breast milk is low in vitamin K. For these reasons, all newborns are recommended to receive a prophylactic vitamin K injection.

Yes, certain medications can interfere with vitamin K. For example, anticoagulant drugs like warfarin block vitamin K's function, while long-term use of certain antibiotics can reduce the gut bacteria that produce vitamin K.

Conditions that cause fat malabsorption, such as cystic fibrosis, celiac disease, and chronic liver disease, are common causes of vitamin K deficiency in adults. These conditions interfere with the absorption of this fat-soluble vitamin from the diet.

A vitamin K supplement, often in the form of phytonadione (K1), restores the body's vitamin K supply. This allows the liver to produce adequate amounts of clotting factors and ensures proper function of other vitamin K-dependent proteins for bone health.

Foods rich in vitamin K include green leafy vegetables like spinach, kale, and broccoli (K1). Sources of Vitamin K2 include fermented foods like natto, and small amounts are found in meat, cheese, and eggs.