Who is most likely to be deficient in vitamin K?

October 17, 2025 •

4 min read

Vitamin K deficiency is considered rare in healthy adults, largely due to its wide availability in food and production by gut bacteria. However, specific populations are at a significantly higher risk, making it crucial to understand who is most likely to be deficient in vitamin K for effective prevention and medical care.

Quick Summary

Explains which populations are at the highest risk for developing vitamin K deficiency, including newborns, individuals with fat malabsorption issues, liver disease, and those on specific medications.

Key Points

Newborns at Highest Risk: Due to low placental transfer, sterile gut, and low levels in breast milk, newborns are most likely to be deficient and receive a prophylactic vitamin K shot.
Fat Malabsorption is a Major Cause in Adults: Chronic conditions such as cystic fibrosis, celiac disease, and liver disease impair the body's ability to absorb fat-soluble vitamins, including vitamin K.
Certain Medications Interfere: Anticoagulant drugs like warfarin and prolonged use of broad-spectrum antibiotics can significantly disrupt vitamin K metabolism or production.
Bleeding is a Key Symptom: Signs of deficiency include easy bruising, excessive bleeding from wounds, nosebleeds, and blood in the urine or stool.
Rare in Healthy Adults: For most healthy adults, a balanced diet is sufficient, and deficiency is uncommon due to natural dietary intake and gut bacteria production.
Prevention is Primarily Dietary: Maintaining a diet rich in leafy greens like kale and spinach is key, especially when combined with a small amount of fat for optimal absorption.

Understanding the High-Risk Populations for Vitamin K Deficiency

Vitamin K is a fat-soluble vitamin essential for blood clotting and bone health. While a balanced diet and natural bacterial synthesis in the intestines protect most healthy adults, certain individuals are highly susceptible to deficiency. The primary risk factors are related to developmental stage (newborns), underlying health conditions, and medication use.

Newborn Infants: The Most Vulnerable

Newborns are the most common group to experience vitamin K deficiency. This is primarily because of three factors:

Low Placental Transfer: Only small amounts of vitamin K are passed from the mother to the fetus during pregnancy, so babies are born with very limited reserves.
Immature Gut Flora: Newborns do not have the intestinal bacteria needed to produce vitamin K2 in the first few days of life.
Low Vitamin K in Breast Milk: Breast milk contains naturally low levels of vitamin K compared to formula.

This is why a single vitamin K shot, known as prophylaxis, is recommended for all newborns shortly after birth to prevent a potentially life-threatening condition called Vitamin K Deficiency Bleeding (VKDB).

Chronic Conditions and Fat Malabsorption

Since vitamin K is a fat-soluble vitamin, its absorption relies on a healthy digestive system. Any condition that impairs the absorption of dietary fats can lead to a deficiency. This includes:

Cystic Fibrosis: This genetic disorder affects mucus production and can lead to pancreatic insufficiency, hindering the absorption of fat-soluble vitamins.
Celiac Disease: An autoimmune disorder where consuming gluten damages the small intestine, impairing nutrient absorption, including vitamin K.
Liver Disease: As clotting factors are produced in the liver, significant liver disease, including biliary tract issues, can disrupt the body's ability to utilize vitamin K effectively.
Inflammatory Bowel Diseases (IBD): Conditions like Crohn's disease can lead to chronic inflammation and malabsorption.
Short Bowel Syndrome or Bariatric Surgery: Surgical removal of parts of the intestine can reduce the area available for absorption.

Medications That Affect Vitamin K

Certain medications can interfere with vitamin K metabolism, increasing the risk of deficiency. The most prominent examples are:

Anticoagulants (like Warfarin): This medication class works by blocking the recycling of vitamin K in the body. Regular monitoring is essential for patients on these drugs.
Broad-Spectrum Antibiotics: Extended use of antibiotics can destroy the bacteria in the gut that produce vitamin K2, reducing overall supply.
Bile Acid Sequestrants: Used to lower cholesterol, these medications can reduce vitamin K absorption if used long-term.

Other Factors Contributing to Deficiency

Besides the major categories above, other circumstances can increase an adult's risk:

Severe Malnutrition: A diet that is severely lacking in vitamin K-rich foods can eventually lead to a deficiency, though this is rare in developed countries.
Alcoholism: Chronic alcohol abuse can impact liver function and overall nutritional status, contributing to deficiency.

Signs and Symptoms of Vitamin K Deficiency

Recognizing the signs of deficiency is vital. The most common symptoms are related to impaired blood clotting:

Easy bruising
Excessive bleeding from wounds, punctures, or injections
Nosebleeds or bleeding gums
Blood in the urine or stool, or dark, tarry stools
Heavy menstrual bleeding in women
In newborns, bleeding around the umbilical cord or circumcision site

Chronic, subclinical deficiency can also impact bone health, leading to decreased bone mineralization over time.

Diagnosis and Treatment

If a deficiency is suspected, a doctor will review medical history and may order a blood test called a prothrombin time (PT) or International Normalized Ratio (INR). A prolonged clotting time can indicate a vitamin K issue. Treatment typically involves administering vitamin K supplements, either orally, subcutaneously, or intravenously, depending on the severity and cause. For malabsorption issues, higher doses may be needed.

Dietary Prevention and Food Sources

The best way for healthy individuals to prevent deficiency is through a balanced diet. Here are some of the richest sources of vitamin K:

Rich Sources of Vitamin K

Green leafy vegetables: Kale, spinach, collard greens, Swiss chard, and turnip greens.
Cruciferous vegetables: Broccoli, Brussels sprouts, and cabbage.
Herbs: Parsley, basil, and cilantro.
Oils: Soybean and canola oil.
Fruits: Blueberries and figs.
Animal products (for K2): Meat, eggs, and cheese.
Fermented foods: Natto (fermented soybeans) is an excellent source of vitamin K2.

Comparison of Major Risk Factors for Vitamin K Deficiency


Risk Group	Primary Reason for Deficiency	Special Considerations
Newborn Infants	Low placental transfer, immature gut flora, low vitamin K in breast milk	Standard prophylactic shot at birth is crucial for prevention.
Fat Malabsorption	Conditions like cystic fibrosis, celiac disease, and chronic liver disease hinder absorption	May require higher-dose supplementation; often related to other fat-soluble vitamin deficiencies.
Anticoagulant Users	Medications like warfarin inhibit vitamin K metabolism	Requires careful dietary management and regular monitoring of INR to prevent complications.
Antibiotic Users	Long-term use can wipe out gut bacteria that produce vitamin K	Deficiency is less common from this alone but can be a contributing factor with other risks.
Severe Malnutrition	Extremely poor dietary intake of vitamin K over time	Often co-occurs with alcoholism or other systemic issues.

Conclusion

While a true vitamin K deficiency is rare in the general, healthy adult population, certain groups face a significantly elevated risk. Newborns, individuals with conditions affecting fat absorption (like cystic fibrosis and celiac disease), those with liver disease, and patients on specific medications like warfarin are particularly vulnerable. Awareness of these risk factors is the first step toward prevention. For most healthy people, ensuring a diet rich in leafy green vegetables and other vitamin K sources is sufficient. However, for at-risk individuals, medical supervision and appropriate supplementation are essential to prevent dangerous bleeding complications and support long-term bone health.

For more detailed information on vitamin K and its functions, refer to the NIH Office of Dietary Supplements fact sheet.

Frequently Asked Questions

No, vitamin K deficiency is very rare in healthy adults. This is because vitamin K is widely available in many foods, particularly green leafy vegetables, and is also produced by bacteria in the intestinal tract.

Newborns are at high risk due to low transfer of vitamin K across the placenta, an immature digestive system without the necessary bacteria, and the low vitamin K content of breast milk.

VKDB is a serious, potentially life-threatening condition that can occur in newborns who do not have enough vitamin K. It is characterized by uncontrolled bleeding and can affect any part of the body.

Vitamin K is a fat-soluble vitamin, so it requires dietary fat for proper absorption. Conditions that impair fat absorption, such as cystic fibrosis, celiac disease, or liver disease, prevent the body from absorbing enough vitamin K, leading to deficiency.

Yes, certain medications, most notably anticoagulants like warfarin, can cause a vitamin K deficiency by blocking its metabolic pathway. Long-term antibiotic use can also reduce the beneficial gut bacteria that produce vitamin K2.

The most common symptoms are related to impaired blood clotting and include easy bruising, excessive bleeding from minor cuts, nosebleeds, bleeding gums, and blood in the urine or stool.

Vitamin K deficiency is typically treated with vitamin K supplements, which can be given orally, subcutaneously, or intravenously. For newborns, a prophylactic injection is standard at birth.