Which Vitamin Deficiency Causes Poor Blood Clotting?

November 27, 2025 •

4 min read

According to the CDC, newborns are at a higher risk for Vitamin K Deficiency Bleeding (VKDB) if they do not receive a prophylactic vitamin K shot at birth. This highlights the critical role of vitamin K in preventing dangerous hemorrhage and addresses the key question of which vitamin deficiency causes poor blood clotting.

Quick Summary

This article details how a deficiency in vitamin K impairs the body's ability to produce crucial clotting factors, leading to poor blood coagulation. It covers the symptoms, causes, diagnosis, and treatment, emphasizing the importance of this fat-soluble vitamin for proper hemostasis.

Key Points

Vitamin K is Essential for Coagulation: A deficiency directly impairs the body's ability to produce critical blood-clotting proteins.
Bleeding is the Primary Symptom: Low vitamin K levels can cause easy bruising, excessive bleeding from cuts, nosebleeds, and blood in stool or urine.
Newborns Are Most Vulnerable: Infants have low vitamin K stores at birth and require a prophylactic injection to prevent a life-threatening condition called Vitamin K Deficiency Bleeding (VKDB).
Malabsorption and Medications are Key Causes: Certain conditions (cystic fibrosis, celiac disease) and drugs (warfarin, long-term antibiotics) can interfere with vitamin K absorption or function.
Rich Dietary Sources Exist: Adequate intake can be achieved through foods like kale, spinach, broccoli, and fermented products like natto.
Diagnosis is Confirmed with a Blood Test: A prothrombin time (PT) test that shows delayed clotting, especially when corrected by vitamin K, confirms the diagnosis.
Vitamin C and D have Different Roles: While other vitamins are important for health, vitamin K is the primary vitamin required for the proper functioning of the blood-clotting cascade.

The Critical Role of Vitamin K in Blood Coagulation

Blood clotting, or coagulation, is a vital process that prevents excessive bleeding after an injury. This complex process relies on a sequence of events involving specific proteins, most of which are produced in the liver. For these proteins to function correctly, a specific vitamin is indispensable: vitamin K.

How Vitamin K Governs Clotting

Vitamin K acts as a crucial co-factor for an enzyme responsible for activating certain clotting factors. Without sufficient vitamin K, the liver produces inactive versions of these proteins, and the coagulation cascade is severely impaired. This functional impairment results in the main clinical manifestation of deficiency: abnormal and excessive bleeding.

There are two primary forms of vitamin K:

Vitamin K1 (phylloquinone): This form is primarily sourced from plant foods, such as green leafy vegetables.
Vitamin K2 (menaquinone): This form is produced by bacteria in the intestinal tract and found in certain animal and fermented foods.

Causes of Vitamin K Deficiency

While dietary deficiency is rare in healthy adults, certain conditions and medications can interfere with vitamin K absorption or metabolism, leading to a deficiency. The most common risk factors include:

Newborns: Infants are born with very low levels of vitamin K because of poor placental transfer and a sterile gut in the first few days of life. A single vitamin K shot at birth is standard prophylaxis.
Malabsorption Disorders: Conditions that interfere with fat absorption, such as cystic fibrosis, celiac disease, or biliary tract disease, can prevent the body from absorbing fat-soluble vitamins like vitamin K.
Medications: Certain drugs, like the blood thinner warfarin, function by antagonizing the action of vitamin K. Long-term antibiotic use can also disrupt the gut bacteria that produce vitamin K2.
Severe Malnutrition or Alcoholism: Poor diet and liver damage can impair the production and storage of clotting factors.

Symptoms of Poor Blood Clotting

The signs of vitamin K deficiency can vary in severity, from minor issues to life-threatening hemorrhage. Common symptoms include:

Easy bruising
Excessive bleeding from minor wounds or puncture sites
Nosebleeds or gum bleeding
Blood in the urine or stool, which may appear dark and tarry
Heavy menstrual bleeding
For infants, bleeding from the umbilical cord stump or circumcision site
The most dangerous complication, especially in infants, is intracranial bleeding, or bleeding into the brain.

Diagnosis and Treatment of Vitamin K Deficiency

Diagnosis of vitamin K deficiency typically involves a physical examination and a blood test called the prothrombin time (PT) test, which measures how long it takes for blood to clot. An abnormally high PT value, especially one that improves rapidly after vitamin K administration, confirms the diagnosis.

Treatment depends on the severity and underlying cause. Mild cases can often be managed through oral supplementation, while more severe bleeding may require a vitamin K injection. For newborns, the standard is a single intramuscular injection shortly after birth.

Dietary Sources of Vitamin K

Maintaining adequate vitamin K intake is the best way to prevent a deficiency. Rich sources include:

Leafy Greens: Spinach, kale, collard greens, turnip greens, and Swiss chard.
Cruciferous Vegetables: Broccoli, Brussels sprouts, and cabbage.
Plant Oils: Soybean and canola oil.
Fermented Foods: Natto (fermented soybeans) is an exceptionally rich source of K2.
Animal Products: Smaller amounts are found in meat, cheese, and eggs.

Comparison: Vitamin K vs. Other Nutrients and Coagulation


Feature	Vitamin K	Vitamin C	Vitamin D	Calcium
Role in Coagulation	Essential cofactor for activating clotting factors (II, VII, IX, X, proteins C and S).	Influences platelet aggregation and vascular health; deficiency (scurvy) can cause fragile capillaries and bleeding.	Influences thrombosis-related pathways, but not a primary clotting factor like vitamin K.	Crucial for proper functioning of vitamin K-dependent proteins; helps chelate calcium for clotting.
Deficiency Impact	Impaired coagulation, excessive bleeding, hemorrhages.	Scurvy, fragile blood vessels, poor wound healing.	Bone health issues (rickets/osteoporosis); recent links to thrombosis.	Impairs many physiological functions, including nerve signaling and bone health; impacts clotting indirectly.
Dietary Sources	Leafy greens, vegetable oils, fermented foods.	Citrus fruits, strawberries, broccoli, bell peppers.	Sunlight, fatty fish, fortified dairy.	Dairy products, leafy greens, fortified foods.
Absorption/Metabolism	Fat-soluble; requires fat for proper absorption. Gut bacteria produce K2.	Water-soluble; easily absorbed and excess is excreted.	Fat-soluble; synthesized in skin with UV light.	Absorbed via intestines; regulated by vitamin D.

Conclusion

Vitamin K is the specific vitamin deficiency that causes poor blood clotting by inhibiting the activation of key coagulation factors produced in the liver. While rare in healthy adults, certain medical conditions like malabsorption disorders, specific medications, and the unique circumstances of newborns can lead to a deficiency. Recognizing the symptoms, understanding the causes, and ensuring a diet rich in vitamin K, especially green leafy vegetables, is crucial for maintaining proper hemostasis and preventing dangerous bleeding episodes. Consult a healthcare provider if you suspect a vitamin deficiency or experience unexplained bleeding.

For more information on the critical function of vitamin K, refer to the Office of Dietary Supplements at NIH.

Frequently Asked Questions

A deficiency in vitamin K is the primary cause of poor blood clotting. Vitamin K is essential for the liver to produce several key proteins, or clotting factors, that are necessary for the coagulation process.

Vitamin K acts as a crucial cofactor for an enzyme that activates clotting factors II, VII, IX, and X. Without sufficient vitamin K, these factors are not properly activated, leading to a dysfunctional clotting cascade and increased bleeding risk.

Yes, a severe vitamin K deficiency can be dangerous and even life-threatening. The main danger is uncontrolled hemorrhage, which can occur internally, particularly intracranial bleeding in infants, or externally from wounds.

Symptoms can include easy bruising, excessive bleeding from small cuts or injections, nosebleeds, bleeding gums, blood in the urine or stool, and heavy menstrual periods.

In healthy adults with a balanced diet, vitamin K deficiency is rare because the vitamin is widely available in many foods, and gut bacteria produce additional amounts. It is more commonly seen in individuals with malabsorption issues, liver disease, or those taking specific medications.

Newborns are at high risk because they are born with very low levels of vitamin K. This is due to poor placental transfer, a sterile gut that has not yet produced vitamin K2, and low vitamin K content in breast milk.

Foods rich in vitamin K include green leafy vegetables like kale and spinach, cruciferous vegetables such as broccoli and Brussels sprouts, vegetable oils, and fermented foods like natto.