What happens if you don't eat vitamin K?

January 6, 2026 •

3 min read

According to the National Institutes of Health, vitamin K deficiency is quite rare in healthy adults who consume a balanced diet, yet it poses significant risks for specific at-risk populations. Understanding what happens if you don't eat vitamin K is crucial to preventing serious health complications, such as life-threatening bleeding and fragile bones.

Quick Summary

A lack of dietary vitamin K can severely impair the body's blood clotting ability, leading to excessive bleeding and easy bruising. Chronic deficiency also compromises bone mineralization and is associated with increased cardiovascular disease risk, especially in at-risk groups.

Key Points

Blood Clotting Failure: The most critical risk is impaired blood coagulation, leading to severe uncontrolled bleeding.
Weakened Bones: Insufficient vitamin K causes poor bone mineralization, increasing osteoporosis and fracture risk.
Infant Vulnerability: Newborns are at risk for Vitamin K Deficiency Bleeding (VKDB); a prophylactic injection at birth is routine.
Increased Heart Risk: Deficiency contributes to arterial calcification, raising cardiovascular disease risk.
Malabsorption is a Major Cause: Digestive disorders can prevent absorption of this fat-soluble vitamin.
Drug Interactions: Certain medications interfere with vitamin K function.

Vitamin K is a fat-soluble vitamin essential for numerous physiological processes, primarily blood coagulation and bone metabolism. It exists in two natural forms: phylloquinone (K1), found mainly in leafy green vegetables, and menaquinones (K2), synthesized by gut bacteria and found in fermented foods and animal products. While most healthy individuals absorb enough through diet and internal production, a deficiency can occur, leading to serious health issues, particularly in newborns and those with specific medical conditions that hinder absorption.

The Role of Vitamin K in Your Body

Vitamin K's critical functions include:

Blood Coagulation: It activates several clotting factors in the liver. Without sufficient vitamin K, blood clotting is impaired, leading to uncontrolled bleeding.
Bone Health: Vitamin K is required for osteocalcin, a protein that helps bind calcium to bones. Deficiency results in poor bone mineralization and contributes to osteoporosis.
Cardiovascular Health: It activates Matrix Gla Protein (MGP), which prevents calcium from accumulating in arteries. Low vitamin K levels may increase the risk of arterial calcification and heart disease.

Serious Consequences of Vitamin K Deficiency

Excessive Bleeding and Hemorrhage

Not getting enough vitamin K impairs blood clotting, which can lead to life-threatening hemorrhaging in severe cases. Bleeding symptoms can include:

Easy Bruising
Mucosal Bleeding (nose, gums, wounds)
Gastrointestinal Bleeding (blood in stool or vomit)
Heavy Menstrual Periods (menorrhagia)
Hemorrhage in Infants (Vitamin K Deficiency Bleeding, VKDB)

Weakened Bones and Osteoporosis

Vitamin K is vital for regulating calcium in bone tissue. Chronic deficiency can lead to lower bone density and increased fracture rates. The body produces an inactive form of osteocalcin, impairing bone mineralization.

Cardiovascular Complications

Inadequate vitamin K is linked to increased cardiovascular disease risks. By failing to activate MGP protein, deficiency allows calcium deposits to form in arteries, making them stiffer and narrower, a risk factor for heart attacks and strokes.

Who Is at Risk for Vitamin K Deficiency?

While healthy adults rarely become deficient, higher risk groups include:

Newborns: Infants have low vitamin K stores. Prophylactic injections prevent VKDB.
Individuals with Malabsorption Disorders: Conditions like cystic fibrosis or celiac disease impair absorption.
People with Liver Disease: Liver damage affects the production of vitamin K-dependent clotting factors.
Patients on Certain Medications: Long-term broad-spectrum antibiotics and the anticoagulant warfarin interfere with vitamin K function.

Preventing and Treating Deficiency

A diet rich in leafy greens, vegetable oils, and certain fermented foods is key for prevention. Treatment for established deficiency involves vitamin K supplementation, given orally, subcutaneously, or via injection. Severe bleeding may require a blood transfusion. For more detailed information on vitamin K, consult authoritative sources like the NIH Office of Dietary Supplements at https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/.

Newborn vs. Adult Deficiency: A Comparison


Feature	Deficiency in Newborns	Deficiency in Adults
Primary Cause	Low placental transfer, low vitamin K in breast milk, and sterile gut at birth	Malabsorption disorders, medication interactions, chronic illness
Symptom Onset	Typically in the first few weeks or months of life	Often slow and gradual, becoming apparent with severe deficiency
Main Symptoms	Severe intracranial bleeding (most dangerous), umbilical bleeding, bruising on face/head	Excessive bruising, bleeding gums, blood in urine or stool, weak bones
Risk of Hemorrhage	High risk, especially without prophylactic injection	Increased risk of internal or external bleeding with severe deficiency
Bone Health Impact	Affects normal bone development	Contributes to lower bone density and osteoporosis
Primary Treatment	Prophylactic injection at birth is standard; subsequent doses may be needed	Addressing underlying cause, dietary changes, oral or injectable supplements

Conclusion

While uncommon in healthy adults, vitamin K deficiency poses significant risks for vulnerable populations. Impaired blood clotting leading to excessive bleeding is the most immediate threat. Long-term implications include weakened bones and increased cardiovascular disease risk. Maintaining adequate intake through diet is the best prevention, with timely medical treatment essential for deficiency. Consult a healthcare provider if deficiency is suspected.

Frequently Asked Questions

The most common sign is excessive bleeding and easy bruising due to impaired blood clotting, potentially including bleeding gums, nosebleeds, or blood in the urine or stool.

Newborn infants are at highest risk. Adults with fat malabsorption disorders, liver disease, or those taking certain medications like warfarin are also at increased risk.

Yes, chronic vitamin K deficiency can impact bone health by impairing bone mineralization, leading to decreased bone density and increased risk of osteoporosis and fractures.

Vitamin K1 is found in green leafy vegetables like kale and spinach. Vitamin K2 is in fermented foods like natto, eggs, cheese, and meat.

Treatment typically involves vitamin K supplementation. In emergency bleeding situations, a blood transfusion may be necessary.

Some studies suggest vitamin K, especially K2, may help delay arterial calcification, but more research is needed.

VKDB is a dangerous condition in newborns with insufficient vitamin K, causing severe bleeding. All infants are routinely given a vitamin K shot at birth to prevent this.