Who is at Risk for Vitamin K Deficiency?

October 31, 2025 •

3 min read

While vitamin K deficiency is quite rare in healthy adults, certain individuals face a significantly higher risk due to specific health conditions, dietary habits, and medications. This fat-soluble vitamin is critical for proper blood clotting and bone health, making a deficiency potentially dangerous.

Quick Summary

An elevated risk of vitamin K deficiency exists for newborns, individuals with malabsorption disorders, and patients on certain medications like blood thinners. Identifying the risk factors and associated symptoms is key to prevention and early intervention.

Key Points

Newborns are most vulnerable: Due to low placental transfer and immature gut bacteria, infants are highly susceptible to Vitamin K Deficiency Bleeding (VKDB).
Malabsorption is a major cause: Conditions that interfere with fat absorption, such as cystic fibrosis and celiac disease, directly impact vitamin K uptake.
Medications can interfere: Long-term antibiotic use and anticoagulants like warfarin can inhibit vitamin K's function and production.
Vitamin K is vital for clotting and bones: A deficiency can lead to abnormal bleeding, bruising, and poor bone mineralization.
Healthy adults are rarely deficient: In a healthy individual with a balanced diet, the deficiency is uncommon due to dietary intake and gut bacteria production.
Dietary sources differ for K1 and K2: Vitamin K1 is found in leafy greens, while K2 is in animal products and fermented foods, with both being essential.
Diagnosis requires professional medical evaluation: If a deficiency is suspected, a healthcare provider can order blood tests to assess clotting and recommend appropriate treatment.

Understanding Vitamin K: Its Function and Forms

Vitamin K is a fat-soluble vitamin essential for several vital bodily processes, most notably blood clotting and bone health. It serves as a co-factor for an enzyme that modifies specific proteins, including prothrombin and osteocalcin, which are crucial for these functions. There are two primary forms of vitamin K: phylloquinone (K1), found predominantly in plant-based foods, and menaquinones (K2), found in animal products and fermented foods and also produced by gut bacteria. A deficiency compromises these critical functions, leading to health issues ranging from easy bruising to severe bleeding.

High-Risk Populations for Vitamin K Deficiency

Several specific groups of people are particularly susceptible to developing a vitamin K deficiency. Understanding these risk factors is the first step toward prevention and management.

Newborns and Infants

Newborns are arguably the most at-risk population for vitamin K deficiency. This is because of limited placental transfer of vitamin K, immature gut flora that haven't started producing K2, and the low vitamin K content in breast milk. This combination can lead to Vitamin K Deficiency Bleeding (VKDB), a potentially life-threatening condition. A vitamin K injection is routinely given to newborns to prevent VKDB.

Individuals with Malabsorption Disorders

Vitamin K is fat-soluble, meaning its absorption relies on the body's ability to absorb dietary fats. Conditions that impair fat absorption significantly increase the risk of deficiency. These include cystic fibrosis, celiac disease, Crohn's disease, ulcerative colitis, and liver disease, which impacts bile production needed for fat absorption.

Patients on Certain Medications

Some medications can interfere with vitamin K metabolism or production, raising the risk of deficiency. Anticoagulants like warfarin inhibit vitamin K's blood-clotting function, requiring careful monitoring. Long-term antibiotic use can reduce the beneficial gut bacteria that produce vitamin K2. Additionally, certain anticonvulsant medications taken by pregnant mothers can increase the risk of VKDB in their infants.

Individuals with Poor Nutritional Intake

A severe and prolonged lack of dietary vitamin K, though uncommon, can lead to deficiency. This is typically seen in cases of severe malnutrition, restricted diets lacking in variety, or extremely low-fat diets.

How Dietary Sources Compare: K1 vs. K2


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinones)
Primary Source	Green leafy vegetables	Animal products, fermented foods, gut bacteria
Absorption Rate	Absorbed less efficiently from plants	Absorbed more readily, particularly MK-7 subtype
Bodily Storage	Primarily stored in the liver, heart, and pancreas	Found in higher concentrations in the brain and kidneys
Key Functions	Primarily associated with blood coagulation	Associated with blood clotting, bone metabolism, and heart health

Symptoms and Diagnosis of Deficiency

Symptoms of vitamin K deficiency can include easy bruising, excessive bleeding, nosebleeds, and blood in urine or stool. VKDB in infants can cause dangerous intracranial hemorrhage. Diagnosis involves reviewing medical history and performing blood tests like prothrombin time (PT) and international normalized ratio (INR) to assess clotting. A healthcare professional can diagnose the deficiency and recommend treatment, potentially including supplementation.

Conclusion

While generally rare in healthy adults with balanced diets, vitamin K deficiency poses a significant risk to specific populations. Newborns, individuals with malabsorption disorders, and those on certain medications are particularly vulnerable. Recognizing these risk factors and symptoms is crucial for early intervention. Routine vitamin K prophylaxis for newborns is a highly effective preventive measure. Adults with underlying health issues should consult a healthcare professional for diagnosis and management to prevent complications. Timely diagnosis and appropriate treatment are key for maintaining health. For more general information on vitamin K, including its role and food sources, you can visit the NIH Office of Dietary Supplements website.

Frequently Asked Questions

Vitamin K deficiency is a condition that occurs when the body does not have enough vitamin K, a fat-soluble vitamin crucial for blood clotting and bone health. Without sufficient vitamin K, blood clotting becomes impaired, leading to symptoms like easy bruising and excessive bleeding.

Newborns are at high risk because only small amounts of vitamin K cross the placenta, their gut bacteria that produce some vitamin K are not yet established, and breast milk contains very little of the vitamin. This puts them at risk for a serious bleeding disorder known as Vitamin K Deficiency Bleeding (VKDB).

A doctor diagnoses vitamin K deficiency by reviewing symptoms and medical history. They will then order blood tests, such as prothrombin time (PT) and International Normalized Ratio (INR), to check how quickly the blood clots.

Yes, certain medications can increase the risk of a deficiency. Long-term use of antibiotics can destroy the gut bacteria that produce vitamin K2, and blood thinners like warfarin are designed to block the vitamin's clotting effects.

Symptoms can include easy bruising, excessive bleeding from cuts or injections, nosebleeds, bleeding from the gums, and blood in the urine or stool. In severe cases, it can also contribute to bone weakening.

Conditions that cause poor fat absorption, or malabsorption, significantly increase the risk. These include celiac disease, cystic fibrosis, Crohn's disease, and liver or gallbladder diseases that affect bile production.

If you experience symptoms like easy bruising or abnormal bleeding, you should consult a healthcare professional. They can conduct tests for an accurate diagnosis and recommend dietary changes or supplementation if needed.