Vitamin K Deficiency
A shortage of the vitamin needed for normal blood clotting
Quick Facts
- Type: Nutritional and clotting disorder
- Key role of vitamin K: Helps blood clot normally
- Main sign: Easy bruising and bleeding
- Most at risk: Newborns and people with malabsorption
Overview
Vitamin K is a nutrient the body uses to make several proteins that allow blood to clot. When vitamin K is low, these clotting proteins do not work properly, so even minor injuries can lead to prolonged bleeding or easy bruising. Vitamin K also plays a role in bone health.
Deficiency is uncommon in healthy adults because vitamin K is found in many foods—especially leafy green vegetables—and is also made by bacteria in the intestine. It is more likely in newborns, in people who cannot absorb fat properly, and in those with liver disease or on certain medications. Most cases respond well to vitamin K supplements once the cause is recognized.
Symptoms
The main effect of low vitamin K is a tendency to bleed or bruise more easily than normal. Possible signs include:
- Easy or excessive bruising
- Bleeding from the gums or nose
- Blood in the urine or stool
- Heavy or prolonged bleeding from small cuts
- Heavy menstrual bleeding in some women
In newborns, vitamin K deficiency can cause serious bleeding, including dangerous bleeding into the brain, which is why a vitamin K injection is routinely given at birth. Any unexplained or severe bleeding should be evaluated promptly.
Causes
Vitamin K deficiency develops when intake, absorption, or use of the vitamin is reduced. Causes include:
- Poor absorption of fat: Conditions such as celiac disease, cystic fibrosis, or bile duct problems reduce uptake of fat-soluble vitamins.
- Liver disease: The liver uses vitamin K to make clotting proteins, so liver damage impairs clotting.
- Medications: Long-term antibiotics can reduce vitamin-K-producing gut bacteria; blood thinners such as warfarin work by blocking vitamin K.
- Newborn status: Babies are born with low vitamin K stores and breast milk contains little of it.
- Very poor diet: Rarely, severely limited food intake contributes.
Risk Factors
- Newborn infants, especially if exclusively breastfed without vitamin K at birth
- Conditions that impair fat absorption (celiac disease, cystic fibrosis, gallbladder or bile duct disease)
- Chronic liver disease
- Long-term antibiotic use
- Use of blood thinners such as warfarin
- Severely restricted diet or malnutrition
Diagnosis
Doctors usually suspect vitamin K deficiency when there is unexplained bleeding or bruising, often together with a known risk factor. Evaluation may include:
- Clotting tests: A prothrombin time (PT) or INR measures how long blood takes to clot and is often prolonged in deficiency.
- Response to vitamin K: Improvement in clotting after giving vitamin K helps confirm the diagnosis.
- Tests for the cause: Assessment of liver function, absorption problems, or medications that may be responsible.
Treatment
Treatment replaces vitamin K and addresses the underlying cause. Approaches include:
- Vitamin K supplements: Given by mouth or, when bleeding is significant or absorption is poor, by injection.
- Treating the cause: Managing liver disease, correcting malabsorption, or reviewing medications that interfere with vitamin K.
- Newborn prevention: A single vitamin K injection at birth prevents bleeding from deficiency.
- Urgent treatment of bleeding: Serious or active bleeding may need vitamin K plus clotting factor replacement in a hospital.
For people on warfarin, vitamin K is used carefully and only as directed, because it counteracts the medication.
Prevention
- Eat vitamin-K-rich foods such as leafy greens (spinach, kale, broccoli) as part of a balanced diet
- Manage conditions that affect fat absorption with medical care
- Ensure newborns receive routine vitamin K at birth
- Take long-term antibiotics only as prescribed
- If on warfarin, keep vitamin K intake steady and follow monitoring instructions
When to See a Doctor
See a doctor for unexplained or frequent bruising, bleeding gums, or nosebleeds. Seek emergency care immediately for:
- Bleeding that will not stop
- Vomiting blood or passing black, tarry, or bloody stools
- Severe headache, confusion, or weakness, which may signal bleeding in the brain
- Any significant bleeding in a newborn
Frequently Asked Questions
What does vitamin K do?
Vitamin K helps the body make proteins that allow blood to clot, so wounds stop bleeding. It also supports bone health. Without enough of it, blood clots less effectively and bleeding or bruising becomes more likely.
Who is most at risk of vitamin K deficiency?
Newborns, people who cannot absorb fat well (such as those with celiac disease or cystic fibrosis), people with liver disease, and those on long-term antibiotics or blood thinners are most at risk. It is uncommon in otherwise healthy adults.
Why do newborns get a vitamin K shot?
Babies are born with very low vitamin K stores and breast milk contains little of it, which can lead to serious bleeding, including in the brain. A single vitamin K injection at birth safely prevents this.
Can I get enough vitamin K from food?
Yes. Leafy green vegetables like spinach, kale, and broccoli are rich in vitamin K, and a balanced diet usually provides plenty. Deficiency from diet alone is rare unless absorption is also impaired.
Is vitamin K deficiency dangerous?
It can be, because it raises the risk of abnormal bleeding. Most cases are treated effectively with supplements, but serious bleeding—such as into the brain—is an emergency that needs immediate care.
References
- National Institutes of Health, Office of Dietary Supplements. Vitamin K.
- MedlinePlus, U.S. National Library of Medicine. Vitamin K.
- Mayo Clinic. Vitamin K.
- Centers for Disease Control and Prevention (CDC). Vitamin K and newborns.