Why Would You Be Low on Vitamin K?

December 25, 2025 •

3 min read

While severe vitamin K deficiency is rare in healthy adults, some studies suggest that a significant portion of the population may have suboptimal vitamin K levels. This can occur for several reasons beyond simple dietary intake, including issues with absorption and underlying health conditions.

Quick Summary

Low vitamin K levels can stem from fat malabsorption disorders, certain medications, and poor dietary intake. Newborns and individuals with liver disease are also at higher risk due to a variety of factors related to storage and production of the vitamin.

Key Points

Fat Malabsorption: Conditions like celiac disease or cystic fibrosis can significantly hinder the absorption of vitamin K from food.
Medication Interference: Anticoagulants like warfarin block vitamin K's activity, while long-term antibiotics can disrupt gut bacteria that produce the vitamin.
Newborn Risk: Infants are born with very low vitamin K reserves and are susceptible to Vitamin K Deficiency Bleeding (VKDB) without a prophylactic injection.
Liver Health: Severe liver disease impairs the liver's ability to produce clotting factors, leading to a functional vitamin K deficiency.
Dietary Considerations: Following a very low-fat diet can inhibit vitamin K absorption, as it is a fat-soluble vitamin.

Understanding the Roles of Vitamin K

Vitamin K is a fat-soluble vitamin essential for several critical bodily functions. Primarily known for its role in blood coagulation, it is necessary for the production of proteins that help blood clot properly. Without sufficient vitamin K, the risk of uncontrolled bleeding increases significantly. Beyond blood clotting, vitamin K is also vital for bone health, aiding in the production of proteins like osteocalcin, which helps bind calcium in the bones. This multifaceted role means a deficiency can affect more than just bleeding risk, also potentially impacting bone density and overall skeletal health.

Medical Conditions Affecting Vitamin K Levels

One of the most significant reasons for low vitamin K is a medical condition that affects the body's ability to absorb or utilize this fat-soluble nutrient. Since vitamin K is absorbed with dietary fats, any condition that impairs fat absorption can lead to a deficiency.

Fat Malabsorption Disorders

Digestive and intestinal diseases that disrupt fat absorption can lead to low vitamin K. These include celiac disease, cystic fibrosis, inflammatory bowel disease (IBD) like Crohn's disease, and biliary tract obstruction. Certain bariatric surgeries can also reduce the area for nutrient absorption, impacting vitamin K levels.

Liver Disease

The liver is crucial for processing vitamin K and producing vitamin-K-dependent proteins. Severe liver disease can lead to deficiency even with adequate intake.

Medications That Interfere with Vitamin K

Several medications can interfere with vitamin K function or production.

Anticoagulants

Blood thinners like warfarin inhibit the vitamin K cycle to prevent clotting. Consistent dietary vitamin K is important while on this medication.

Antibiotics

Long-term use of broad-spectrum antibiotics can reduce gut bacteria that produce vitamin K2, temporarily lowering levels.

Other Drugs

Some cholesterol and anti-seizure medications can also impact vitamin K.

Dietary and Lifestyle Factors

A diet low in vitamin K-rich foods or very low in fat can contribute to deficiency, especially with other risk factors.

The Unique Case of Newborns

Newborns are prone to Vitamin K Deficiency Bleeding (VKDB) due to poor placental transfer, low levels in breast milk, and a lack of gut bacteria to produce vitamin K2. A routine vitamin K injection is given to prevent VKDB.

Comparison Table: Causes of Vitamin K Deficiency


Cause Type	Specific Condition / Factor	Mechanism of Action	At-Risk Population	Note
Malabsorption	Celiac Disease, Cystic Fibrosis	Impaired fat absorption in the intestines	Individuals with these diagnoses	Requires medical diagnosis and management
Medical	Liver Disease	Impaired synthesis of vitamin K-dependent proteins	Individuals with chronic liver conditions	Severity depends on liver function
Medication	Warfarin (Anticoagulant)	Inhibits the vitamin K cycle	Patients taking blood thinners	Requires careful dietary consistency
Medication	Long-term Antibiotics	Disrupts gut bacteria that produce K2	Individuals on prolonged antibiotic therapy	Often a temporary effect
Dietary	Very Low-Fat Diet	Impedes the absorption of fat-soluble vitamins	Individuals on restrictive diets	Pairing K-rich foods with healthy fats helps
Newborn	Low Stores, Sterile Gut	Insufficient transfer, gut bacteria	All newborns, especially breastfed	Prevented by prophylactic injection

Conclusion

Low vitamin K levels, though uncommon in healthy adults, can seriously affect vulnerable groups like newborns or those with specific health conditions or on certain medications. Understanding the reasons why you might be low on vitamin K is key to prevention and management. Consulting a healthcare provider is vital for monitoring and addressing potential deficiencies.

Learn more about the vitamin K cycle and its importance for coagulation at National Institutes of Health (NIH) Office of Dietary Supplements.

Frequently Asked Questions

In healthy adults, deficiency is rare because the vitamin is widely available in green leafy vegetables and produced by gut bacteria. However, underlying medical conditions that cause fat malabsorption are the most common cause for a deficiency.

Long-term or high-dose antibiotic use can kill off the beneficial gut bacteria that produce vitamin K2. This can lead to a temporary decrease in the body's overall vitamin K levels.

Yes, a diet severely lacking in vitamin K-rich foods, particularly green leafy vegetables, or a very low-fat diet can contribute to a deficiency because vitamin K is a fat-soluble vitamin that requires fat for proper absorption.

Newborns have low vitamin K reserves from birth, and breast milk provides only small amounts. Their intestines also lack the bacteria to produce the vitamin themselves, making them susceptible to Vitamin K Deficiency Bleeding (VKDB).

The liver is responsible for synthesizing crucial vitamin K-dependent clotting factors. Severe liver disease impairs this function, leading to a functional deficiency even if there is enough vitamin K available in the body.

Taking warfarin does not mean you have a dietary deficiency, but it does mean the medication is deliberately blocking the action of vitamin K to prevent blood clots. It's vital to keep your vitamin K intake consistent to maintain the drug's effectiveness.

The primary signs are related to blood clotting issues, including easy bruising, nosebleeds, and excessive bleeding from wounds. In severe cases, bleeding can occur internally or in the brain.