Who is most affected by vitamin K deficiency?

November 21, 2025 •

4 min read

According to the Centers for Disease Control and Prevention (CDC), vitamin K deficiency bleeding (VKDB) can affect up to 1 in 14,000 to 1 in 25,000 exclusively breastfed infants in the U.S. without a prophylactic injection, highlighting that newborns are the most vulnerable group for vitamin K deficiency. Other at-risk groups include those with certain medical conditions or on specific medications.

Quick Summary

Infants, particularly those who are exclusively breastfed and do not receive a vitamin K shot at birth, are at high risk for vitamin K deficiency bleeding. Certain adults with fat malabsorption disorders, liver disease, or who are taking specific anticoagulant or antibiotic medications are also susceptible due to impaired absorption or metabolism.

Key Points

Newborns are the most affected group: Due to low placental transfer, low vitamin K in breast milk, and underdeveloped gut bacteria, infants are highly susceptible to deficiency and require a prophylactic shot at birth.
Fat malabsorption is a major adult risk factor: Conditions like celiac disease, cystic fibrosis, and Crohn's disease disrupt the body's ability to absorb fat-soluble vitamin K.
Certain medications interfere with vitamin K: Long-term antibiotic use and anticoagulant therapy (e.g., warfarin) can cause or worsen a deficiency.
Liver health is critical for vitamin K function: Liver disease, such as cirrhosis, prevents the synthesis of vitamin K-dependent clotting factors, increasing bleeding risk.
Subclinical deficiency has long-term health implications: Even without severe bleeding, low vitamin K status is linked to poor bone health and increased cardiovascular risk in some populations, including the elderly.
Exclusive breastfeeding is a risk factor for infants: Without a vitamin K shot, exclusively breastfed infants are at a significantly higher risk for late-onset vitamin K deficiency bleeding.

Newborns: The Highest Risk Group

Newborn infants are by far the most affected demographic when it comes to vitamin K deficiency, a condition that can cause dangerous, life-threatening bleeding. The reasons for this high susceptibility are multifold and relate directly to the newborn's physiology.

Low Placental Transfer: Only a small amount of vitamin K is able to cross the placenta from the mother to the fetus during pregnancy, leaving the baby with limited stores at birth.
Immature Gut Flora: The beneficial bacteria in a newborn's intestines, which produce a form of vitamin K called menaquinone (K2), have not yet developed.
Low Vitamin K in Breast Milk: Breast milk contains significantly lower levels of vitamin K compared to cow's milk and formula, putting exclusively breastfed babies at a much higher risk if they do not receive a vitamin K injection.
Preventative Measures: To combat this, a single, prophylactic vitamin K injection is routinely administered to newborns at birth. The risk of developing late-onset vitamin K deficiency bleeding (VKDB) is 81 times greater in infants who do not receive this injection.

Types of Vitamin K Deficiency Bleeding in Infants

Vitamin K deficiency bleeding (VKDB) in infants is classified into three types, depending on when the bleeding occurs:

Early-Onset VKDB: Occurs within the first 24 hours of birth and is severe. It is often linked to the mother taking certain medications during pregnancy, such as anti-seizure drugs.
Classic-Onset VKDB: Occurs between 2 and 7 days after birth. Symptoms include bruising and bleeding from the umbilical cord.
Late-Onset VKDB: Occurs between 2 weeks and 6 months after birth. This type is most common in exclusively breastfed infants who did not receive the vitamin K shot. It is also the most dangerous, with intracranial hemorrhage being a significant risk.

Adult Populations at Risk

While significantly rarer in healthy adults, certain conditions and medications can lead to vitamin K deficiency.

Malabsorption Disorders: Conditions that impair the absorption of dietary fat can also hinder the absorption of fat-soluble vitamins like vitamin K. This includes:
- Cystic Fibrosis: Affects the pancreas, leading to an inability to absorb nutrients.
- Celiac Disease: An autoimmune disorder that damages the small intestine and prevents proper nutrient absorption.
- Crohn's Disease and Ulcerative Colitis: Chronic inflammatory bowel diseases that can reduce nutrient uptake.
- Cholestatic Liver Disease: Impairs the flow of bile, which is essential for fat and vitamin K absorption.
Medications: Several types of drugs can interfere with vitamin K metabolism or production:
- Anticoagulants (e.g., Warfarin): These medications are designed to block the function of vitamin K in the liver to prevent blood clotting. Patients on these drugs must carefully manage their vitamin K intake.
- Antibiotics: Long-term use of broad-spectrum antibiotics can kill the gut bacteria that produce vitamin K, especially in individuals with poor dietary intake.
- Cholestyramine: A cholesterol-lowering medication that binds to bile acids, reducing the absorption of fat-soluble vitamins.
Dietary Factors and Lifestyle: Although rare in healthy adults, those with severe malnutrition, alcoholism, or on long-term total parenteral nutrition without supplementation are at risk.

Comparison of Risk Factors for Deficiency


Risk Group	Primary Cause	Key Contributing Factor	Primary Health Risk
Newborn Infants	Poor placental transfer and immature systems.	Exclusively breastfeeding without prophylactic shot.	Hemorrhagic disease of the newborn (VKDB), including intracranial hemorrhage.
Fat Malabsorption (e.g., Celiac, CF)	Impaired absorption of fat-soluble vitamins.	Underlying gastrointestinal or liver disease.	Increased bleeding risk, potential for osteopenia.
On Warfarin Therapy	Medication actively blocks vitamin K's clotting function.	Inconsistent vitamin K intake from diet.	Excessive bleeding or hemorrhage if intake fluctuates.
On Long-Term Antibiotics	Destruction of gut bacteria that produce vitamin K.	Poor dietary intake of vitamin K-rich foods.	Increased bleeding risk in vulnerable individuals.
Elderly Adults	Potential for poor diet, medication use, and underlying conditions.	Reduced mobility, malnutrition, and polypharmacy.	Potential for suboptimal bone health and increased fracture risk.

The Role of Liver Health

Because the liver is where vitamin K is used to produce clotting factors, any condition that affects liver function can lead to a deficiency, even if dietary intake is adequate. Patients with severe parenchymal liver disease, such as cirrhosis, have impaired synthesis of these clotting factors, which can't be corrected by vitamin K supplementation alone. For these individuals, severe bleeding may require the administration of fresh frozen plasma.

Subclinical Deficiency

Beyond the severe cases, a subclinical or functional vitamin K deficiency is more prevalent, particularly in some high-risk adult populations like the elderly or those with chronic kidney disease. This lower-grade deficiency does not cause noticeable bleeding but is linked to potential long-term health issues. Research suggests it may be a risk factor for conditions such as osteoporosis, due to reduced bone mineralization, and cardiovascular disease through its effect on arterial calcification.

Conclusion

While clinically significant vitamin K deficiency is rare in healthy adults with a balanced diet, several populations face a heightened risk. Newborn infants, with their undeveloped physiological systems, are the most vulnerable group, necessitating a prophylactic injection at birth to prevent life-threatening bleeding. In adults, those with malabsorption syndromes, liver disease, or on specific medications like warfarin and certain antibiotics are also at considerable risk. Recognizing these at-risk groups is crucial for proper screening and preventative care. For adults, maintaining a consistent, vitamin K-rich diet, while managing underlying conditions and medication use, is key to preventing complications.

Visit the CDC website for more information on newborn vitamin K prophylaxis

Frequently Asked Questions

The most notable sign of a vitamin K deficiency is excessive bleeding, which can range from easy bruising and nosebleeds to dangerous internal hemorrhages.

Newborns have low vitamin K stores at birth because the vitamin does not cross the placenta efficiently. They also lack the gut bacteria that produce vitamin K, and breast milk contains low amounts of the vitamin.

The standard prevention method is a single vitamin K injection given to all newborns shortly after birth. This significantly reduces the risk of vitamin K deficiency bleeding.

Yes, some medications can cause a deficiency. Long-term use of broad-spectrum antibiotics can disrupt gut bacteria, and anticoagulants like warfarin intentionally inhibit vitamin K's function.

Fat malabsorption disorders are the main culprits. Conditions such as celiac disease, cystic fibrosis, and certain liver diseases can prevent the body from properly absorbing the fat-soluble vitamin.

Yes, vitamin K is essential for producing proteins involved in bone mineralization. A subclinical deficiency is linked to reduced bone density and a higher risk of fractures in the elderly.

Treatment involves administering vitamin K, either orally or via injection, and addressing the underlying cause. In severe bleeding cases, blood transfusions may be necessary.