Who Gets Vitamin K Deficiency? Understanding Risk Factors

November 18, 2025 •

4 min read

While vitamin K deficiency is rare in healthy adults, it is surprisingly common and dangerous among certain vulnerable populations, most notably newborns. In adults, the condition typically results from underlying medical issues or specific medication usage rather than a poor diet alone. Understanding who is most at risk is crucial for prevention and early detection.

Quick Summary

Primary risk groups for vitamin K deficiency include newborns and adults with conditions affecting nutrient absorption like cystic fibrosis or liver disease, as well as those taking specific medications such as anticoagulants.

Key Points

Newborns are the most vulnerable: Due to low placental transfer, sterile guts, and low vitamin K content in breast milk, newborns are at high risk for dangerous bleeding without a prophylactic shot.
Malabsorption is a primary cause in adults: Conditions like cystic fibrosis, celiac disease, and chronic inflammatory bowel diseases impair the absorption of fat-soluble vitamin K.
Liver disease impacts synthesis: As the liver synthesizes vitamin K-dependent clotting factors, impaired liver function can lead to deficiency despite adequate dietary intake.
Certain medications interfere: Anticoagulants like warfarin block vitamin K activity, while broad-spectrum antibiotics can wipe out the gut bacteria that produce vitamin K.
Dietary intake is key for healthy adults: A varied diet rich in leafy greens is typically sufficient for healthy adults, as deficiency from diet alone is uncommon.
Symptoms include excessive bleeding and easy bruising: The telltale sign of vitamin K deficiency is impaired blood clotting, which manifests as easy bruising, nosebleeds, and in severe cases, dangerous internal bleeding.

Newborns: The Most Vulnerable Population

Newborn infants are by far the highest-risk group for vitamin K deficiency bleeding (VKDB). The Centers for Disease Control and Prevention (CDC) reports that without a prophylactic vitamin K shot at birth, an infant is at risk for this severe bleeding disorder. There are several key reasons for a newborn's vulnerability:

Poor Placental Transfer: Only small amounts of vitamin K cross the placenta from mother to fetus during pregnancy, leaving the newborn with very limited stores.
Low Vitamin K in Breast Milk: Breast milk contains relatively low levels of vitamin K compared to formula milk, which is fortified. Exclusively breastfed infants who do not receive a vitamin K shot are at a higher risk for late-onset VKDB.
Sterile Gut: A newborn's intestinal tract is initially sterile and lacks the bacteria that produce vitamin K2. This gut flora doesn't become established until several days or weeks after birth.
Immature Liver: A newborn's liver is not yet fully mature, which affects its ability to efficiently utilize and store vitamin K.

Why the Neonatal Risk is Critical

The risk of life-threatening bleeding into the brain (intracranial hemorrhage) is a major concern with newborn vitamin K deficiency. Because warning signs are often absent, mandatory vitamin K injections for newborns were established to prevent this serious and preventable condition.

Adults with Malabsorption Disorders

Vitamin K is a fat-soluble vitamin, meaning its absorption depends on the body's ability to absorb dietary fat. For adults, chronic conditions that impair fat absorption, or malabsorption disorders, are a significant risk factor for deficiency. These include:

Cystic Fibrosis: Pancreatic insufficiency in people with CF severely limits the absorption of fat-soluble vitamins. Vitamin K deficiency is a known complication, and routine supplementation is often recommended.
Biliary Tract Disease: Conditions that obstruct bile flow, such as blocked bile ducts or primary biliary cirrhosis, prevent bile from reaching the intestine. Since bile is essential for fat and fat-soluble vitamin absorption, a deficiency can occur.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can reduce vitamin K absorption due to chronic inflammation and damage to the intestinal lining.
Gastrointestinal Surgery: Surgical resection of a part of the intestine can decrease the surface area available for nutrient absorption.
Celiac Disease: This autoimmune disease can cause damage to the lining of the small intestine, leading to malabsorption if not properly managed through a gluten-free diet.

Individuals with Liver Disease

The liver plays a crucial role in vitamin K metabolism and the synthesis of vitamin K-dependent clotting factors. As such, severe liver disease can cause vitamin K deficiency even if dietary intake is adequate. The damaged liver cannot produce the necessary clotting proteins, leading to impaired blood clotting and increased bleeding risk. This is particularly dangerous for patients with conditions like liver cirrhosis.

Individuals Taking Certain Medications

Specific drugs can interfere with vitamin K's function or absorption, increasing the risk of deficiency:

Anticoagulants (e.g., Warfarin): These medications, often called blood thinners, function by blocking the activity of vitamin K. This is a deliberate medical strategy to prevent blood clots in patients with conditions like atrial fibrillation. However, careful management and monitoring are required to balance clotting risk.
Broad-Spectrum Antibiotics: Prolonged use of antibiotics can destroy the bacteria in the gut that produce menaquinone (vitamin K2), leaving some individuals at risk, especially those with poor nutritional intake.
Other Medications: Certain antiseizure drugs and some salicylates have also been associated with an increased risk of vitamin K deficiency.

Comparison of Major Risk Groups


Risk Group	Primary Cause of Deficiency	Key Symptoms/Manifestations	Prevention/Treatment Strategy
Newborns	Low placental transfer, sterile gut, low breast milk content	Vitamin K Deficiency Bleeding (VKDB), severe bruising, bleeding (umbilical cord, brain)	Prophylactic vitamin K shot at birth
Malabsorption	Impaired fat absorption due to underlying disease (e.g., CF, Celiac)	Easy bruising, excessive bleeding, intestinal bleeding, osteoporosis	Addressing underlying condition, oral or parenteral vitamin K supplements
Liver Disease	Impaired synthesis of clotting factors by the liver	Bleeding, bruising, prolonged bleeding time	Addressing underlying liver condition, higher doses of vitamin K may be needed
Medication Users	Blockage of vitamin K function or destruction of gut bacteria (e.g., Warfarin, antibiotics)	Bleeding complications, easy bruising	Careful dosage monitoring and potential supplementation

Prevention and Conclusion

For most healthy adults, a balanced diet rich in vitamin K is sufficient to prevent deficiency. Good sources include leafy green vegetables like kale, spinach, and broccoli, as well as meat, eggs, and fermented foods. However, prevention for high-risk groups involves targeted interventions.

The most important preventive measure is the routine vitamin K shot administered to newborns at birth to prevent life-threatening VKDB. For individuals with malabsorption issues, liver disease, or those on certain medications, medical management is essential. This often includes oral or injected vitamin K supplements, alongside addressing the underlying health condition. While a healthy lifestyle can support optimal vitamin K levels, those in at-risk categories must work closely with healthcare providers to ensure their needs are met and complications are avoided.

For more information on preventing vitamin K deficiency in newborns, consult the official guidelines from the CDC.

Frequently Asked Questions

The most common cause in newborns is the low level of vitamin K passed from the mother to the fetus through the placenta and the lack of gut bacteria to produce the vitamin after birth.

Symptoms in adults can include easy bruising, excessive bleeding from wounds or gums, heavy menstrual periods, and blood in the urine or stool.

Yes, prolonged use of broad-spectrum antibiotics can alter the gut flora responsible for producing vitamin K2, which can contribute to a deficiency, especially in individuals with poor dietary intake.

The liver is where vitamin K-dependent clotting factors are synthesized. When liver function is impaired by disease, it cannot produce these clotting factors, leading to a deficiency.

No, it is very rare in healthy adults who eat a balanced diet. The body recycles vitamin K efficiently, and it is found in many foods and produced by gut bacteria.

Treatment typically involves administering vitamin K, either orally or via injection, along with addressing any underlying conditions contributing to the deficiency.

Cystic fibrosis often causes pancreatic insufficiency, which leads to fat malabsorption. Since vitamin K is fat-soluble, its absorption is significantly hindered.