What happens if you don't have vitamin K? Symptoms, risks, and treatment

November 24, 2025 •

3 min read

According to the National Academy of Science Food and Nutrition Board, clinical vitamin K deficiency is rare in healthy adults but is a serious concern for newborns. A lack of this essential nutrient can impair blood clotting and lead to significant health issues. Understanding what happens if you don't have vitamin K is crucial for recognizing the symptoms and seeking timely treatment.

Quick Summary

A deficiency in vitamin K impairs blood clotting, causing easy bruising, excessive bleeding, and potential bone health problems. Certain medical conditions, long-term antibiotic use, and poor diet can increase the risk of deficiency in adults, while newborns are especially vulnerable.

Key Points

Impaired Blood Clotting: Without enough vitamin K, the body cannot produce the clotting factors needed to stop bleeding, leading to easy bruising and excessive bleeding from wounds.
Risk to Newborns: Newborns are especially vulnerable to vitamin K deficiency bleeding (VKDB) due to low vitamin K levels at birth, which is why a routine injection is recommended.
Risk Factors: Adults at higher risk include those with fat malabsorption disorders, liver disease, or those taking certain medications like anticoagulants or long-term antibiotics.
Impact on Bones: A deficiency can weaken bones over time as vitamin K is vital for proper bone mineralization, increasing the risk of osteoporosis.
Easy to Treat: Deficiency is diagnosed with blood tests and is typically corrected with oral or injectable vitamin K supplementation, along with dietary changes.
Prevention is Key: Eating a balanced diet rich in leafy greens, eggs, and fermented foods provides sufficient vitamin K for most healthy adults.

The Critical Role of Vitamin K

Vitamin K is a fat-soluble vitamin crucial for blood clotting and bone health. The two main forms are vitamin K1 (phylloquinone), found in plants, and vitamin K2 (menaquinones), produced by gut bacteria and found in animal and fermented foods. The body uses vitamin K to create clotting factors in the liver and activate proteins for bone mineralization.

Symptoms of Vitamin K Deficiency

The primary symptom of vitamin K deficiency is excessive bleeding due to impaired blood clotting. While severe deficiency is uncommon in healthy adults, certain factors increase risk. Symptoms can vary:

Common signs in adults:

Easy bruising
Prolonged bleeding from wounds or injections
Nosebleeds or bleeding gums
Heavy menstrual periods
Blood in urine or stool
Petechiae (small red or purple spots under the skin)

Critical concerns for newborns:

Newborns have low vitamin K levels at birth and are at high risk of Vitamin K Deficiency Bleeding (VKDB), which can cause serious, life-threatening bleeding, including within the brain. A vitamin K injection at birth prevents VKDB.

Causes and Risk Factors

Several factors can interfere with vitamin K absorption and metabolism.


Table: Risk Factors for Vitamin K Deficiency	Risk Factor	Reason for Increased Risk
Newborns	Low transfer across the placenta, underdeveloped gut bacteria, low breast milk content.
Fat Malabsorption	Conditions affecting fat absorption (e.g., cystic fibrosis, celiac disease, biliary obstruction) impair absorption of fat-soluble vitamins.
Medications	Warfarin (a vitamin K antagonist); long-term antibiotics reducing gut bacteria producing K2.
Liver Disease	Impaired production of clotting factors.
Poor Diet	Rare in developed countries, but severe malnutrition or low-fat diets can contribute.
Bariatric Surgery	Procedures that limit nutrient absorption.

Diagnosis and Treatment

Diagnosis involves reviewing symptoms and using blood tests like the prothrombin time (PT) test to measure clotting speed. An elevated INR with prolonged PT suggests a deficiency. Improvement after a vitamin K injection confirms the diagnosis.

Treatment depends on severity and cause. Supplementation (oral or injection) is common. Severe bleeding may require fresh frozen plasma. Dietary changes, such as increasing leafy greens, are also recommended. Newborns receive a standard injection at birth. Early detection and treatment usually lead to a good prognosis.

Prevention Through Diet and Management

A balanced diet prevents deficiency in adults. Medical supervision is key for those with underlying conditions or on specific medications.

Sources of Vitamin K1 (Phylloquinone):

Green leafy vegetables (kale, spinach, broccoli)
Soybean and canola oil
Lettuces, cabbage, parsley

Sources of Vitamin K2 (Menaquinones):

Natto
Eggs, chicken, some cheeses
Fermented foods

Consuming vitamin K-rich foods with a little fat aids absorption. The standard newborn injection is the most effective prevention for infants.

Conclusion

Not having enough vitamin K seriously impacts blood clotting and bone health. While uncommon in healthy adults, deficiency is critical for newborns and individuals with certain risk factors, leading to excessive bleeding. Diagnosis via blood tests and treatment with supplements are effective. Preventing VKDB in newborns with an injection at birth is standard practice. Recognizing symptoms and managing risks are vital for health. For more information on vitamin K, consult the National Institutes of Health (NIH) Office of Dietary Supplements.

What is the difference between vitamin K1 and K2?

K1 (phylloquinone): Found in leafy greens, involved in blood clotting. K2 (menaquinones): From gut bacteria, fermented and animal foods, involved in bone and cardiovascular health.

How is vitamin K deficiency diagnosed?

Diagnosis: Based on medical history, symptoms, and blood tests like the prothrombin time (PT) test measuring clotting speed.

Who is at risk for vitamin K deficiency?

Risk factors: Newborns, individuals with fat malabsorption, liver disease, or those taking specific medications like warfarin or long-term antibiotics.

Can a person get too much vitamin K?

No evidence of harm: High doses from food or supplements are generally not harmful, but those on warfarin need consistent intake.

What are the most common symptoms of a deficiency?

Common symptoms: Easy bruising, excessive bleeding, nosebleeds, bleeding gums, blood in urine or stool, and heavy menstrual periods.

How long does it take to correct a vitamin K deficiency?

Correction time: Varies, but improvements in clotting time can be seen within hours of supplementation.

Why is vitamin K deficiency dangerous in newborns?

Newborn danger: Can cause severe bleeding, including in the brain (VKDB), which can be life-threatening.

How can a vitamin K deficiency be prevented?

Prevention: Healthy adults can prevent it with a balanced diet. Newborns receive a preventive injection at birth.

Frequently Asked Questions

If you don't have vitamin K, your body cannot properly form blood clots. This can lead to excessive bleeding, easy bruising, nosebleeds, and in severe cases, dangerous hemorrhages.

Yes, a severe lack of vitamin K can cause serious health complications. In adults, it can increase the risk of poor bone development and osteoporosis. In newborns, it can lead to life-threatening bleeding inside the skull.

Yes, newborns are at a high risk for vitamin K deficiency because they are born with limited stores of the vitamin. Their intestines also lack the bacteria that produce vitamin K2 in adults.

A vitamin K deficiency is treated with supplements of vitamin K, often in the form of an oral dose or an injection, depending on the severity. Treating any underlying medical condition is also part of the management.

Foods rich in vitamin K1 include leafy greens like kale, spinach, and broccoli. Sources of vitamin K2 include fermented foods like natto, as well as eggs, cheese, and chicken.

Anticoagulant medications like warfarin are designed to interfere with vitamin K's clotting function. Long-term use of antibiotics can also disrupt the gut bacteria that produce vitamin K2.

In most healthy adults, a balanced diet is sufficient to prevent deficiency. In newborns, a single vitamin K injection at birth is a routine and effective preventive measure.

The first signs of a deficiency often relate to bleeding, such as easy bruising, small red spots under the skin (petechiae), or prolonged bleeding from minor cuts.