ConditionBlood & immune system
Vitamin K Deficiency
Vitamin K deficiency is a shortage of vitamin K, which the liver needs to make several blood-clotting proteins. Without enough, blood clots slowly, causing easy bruising and bleeding from the gums, nose, gut or urinary tract. It is most important in newborns, who are born with low vitamin K and can develop dangerous bleeding, including in the brain, unless they receive a vitamin K shot at birth. In adults it is uncommon and usually linked to poor absorption, long antibiotic courses, liver disease or very poor diet.
Also called: Hypovitaminosis K, low vitamin K, vitamin K deficiency bleeding (VKDB) in infants
At a glance
- What it does
- Vitamin K activates clotting factors II, VII, IX and X, plus proteins C and S.
- Who is at risk
- Newborns, especially without the birth shot. Adults with malabsorption, long antibiotic use, liver disease or poor intake.
- Signs
- Easy bruising, oozing from cuts or injection sites, nosebleeds, gum bleeding, blood in urine or stool.
- Diagnosis
- Prolonged prothrombin time (PT/INR) that corrects with vitamin K.
- Treatment and prevention
- Vitamin K by mouth or injection. A single shot at birth prevents newborn bleeding.
When to get help
Call 911 or go to the ER
- A baby with unusual sleepiness, vomiting, seizures, a bulging soft spot or poor feeding (possible bleeding in the brain): call 911 or your local emergency number
- Vomiting blood, black or bloody stools, or heavy bleeding that will not stop
- Severe headache or confusion in someone with a bleeding problem
See a doctor within a day or two
- A baby with bruising, bleeding from the umbilical cord stump, nose or gums, or blood in the diaper, especially if they did not get a vitamin K shot at birth
- A baby who is still yellow (jaundiced) after 2 to 3 weeks of age, or has pale stools
- New easy bruising or bleeding in an adult taking long-term antibiotics or with malabsorption
- Bleeding while taking warfarin, or a high INR result
Book a routine appointment
- Chronic diarrhea, celiac disease, cystic fibrosis, weight-loss surgery or liver disease with easy bruising
- Planning to decline the newborn vitamin K shot: discuss risks with your pediatrician
What vitamin K does
Vitamin K is needed to activate several clotting factors made in the liver. Without it, the liver produces inactive versions, and blood takes longer to clot. Vitamin K also plays a role in bone health.
There are two main forms:
- Vitamin K1 (phylloquinone): in leafy green vegetables such as kale, spinach, collards and broccoli, and in some vegetable oils
- Vitamin K2 (menaquinones): made by gut bacteria and found in fermented foods and some animal products
The body stores only small amounts, so deficiency can develop within weeks if intake or absorption stops.
Vitamin K deficiency in newborns
Babies are born with low vitamin K because little crosses the placenta, breast milk contains low levels, and their gut bacteria are not yet established. Without prevention, some develop vitamin K deficiency bleeding (VKDB):
| Type | Timing | Features |
|---|---|---|
| Early | First 24 hours | Usually linked to certain medicines taken in pregnancy, such as some anti-seizure drugs |
| Classic | Days 2 to 7 | Bleeding from the cord, gut, skin or circumcision site |
| Late | 2 to 12 weeks, up to 6 months | Often bleeding in the brain, with lasting damage or death. Most common in exclusively breastfed babies who did not receive the shot, and in babies with liver or absorption problems |
The CDC and American Academy of Pediatrics recommend a single vitamin K injection for every newborn shortly after birth. It is safe and very effective. Babies who do not receive it are many times more likely to develop VKDB. Oral vitamin K regimens are less effective than the injection.
Babies with prolonged jaundice or pale stools may have a liver problem that blocks vitamin K absorption and need urgent assessment.
Causes in adults
- Malabsorption: celiac disease, cystic fibrosis, inflammatory bowel disease, short bowel syndrome, chronic pancreatitis and weight-loss surgery
- Blocked bile flow: bile is needed to absorb fat-soluble vitamins
- Long-term antibiotics, which reduce vitamin K-producing gut bacteria, especially with poor food intake
- Very poor diet, including in hospital patients who are not eating, alcohol use disorder and eating disorders
- Liver disease, which reduces production of clotting factors even with enough vitamin K
- Medicines: warfarin works by blocking vitamin K. Excess warfarin causes the same bleeding pattern (warfarin toxicity). Some cephalosporin antibiotics, high-dose vitamin E and orlistat can also interfere
Symptoms
- Easy bruising and small bruises without injury
- Bleeding from the gums or nose
- Oozing from cuts, injection sites or after procedures
- Heavy menstrual periods
- Blood in the urine or stool, or black stools
- In babies: bleeding from the cord stump, nose or gums, bruising, blood in stools or vomit, and signs of brain bleeding such as sleepiness, poor feeding, vomiting and seizures
Diagnosis
- Prothrombin time (PT) and INR: prolonged
- Activated partial thromboplastin time (aPTT): may also be prolonged
- Response to vitamin K: PT corrects within hours to a day after vitamin K, confirming the diagnosis
- PIVKA-II (inactive prothrombin) testing in some cases
- Tests for the cause: liver function, celiac antibodies, and stool tests for fat malabsorption
Treatment
- Vitamin K (phytonadione): given by mouth, injection or IV depending on severity and absorption. IV vitamin K works within hours.
- Fresh frozen plasma or prothrombin complex concentrate for active serious bleeding, to replace clotting factors immediately.
- Treat the underlying cause: manage malabsorption, adjust antibiotics, improve nutrition.
- Ongoing supplements for people with chronic malabsorption.
People taking warfarin
Do not change how much vitamin K you eat suddenly. Aim for a consistent intake from week to week, and tell your anticoagulation clinic about diet changes or new supplements.
Prevention
- The vitamin K shot for all newborns
- A varied diet with leafy greens
- Supplements as prescribed for people with malabsorption or on long-term nutrition support
Frequently asked questions
What are the symptoms of vitamin K deficiency?
The main symptoms are easy bruising and bleeding: nosebleeds, bleeding gums, oozing from cuts, heavy periods, and blood in the urine or stool. In babies, signs include bleeding from the umbilical cord or nose, bruising, and serious signs of brain bleeding such as sleepiness, vomiting and seizures.
Why do newborns get a vitamin K shot?
Newborns have very low vitamin K at birth, and breast milk contains little. Without supplementation, some babies develop vitamin K deficiency bleeding, which can cause bleeding in the brain. A single vitamin K injection at birth safely prevents this.
What causes vitamin K deficiency in adults?
In adults it is uncommon and usually caused by poor absorption from conditions like celiac disease, cystic fibrosis or bile duct blockage, long courses of antibiotics, very poor diet, liver disease, or weight-loss surgery. Warfarin causes a similar effect by blocking vitamin K.
Which foods are high in vitamin K?
Leafy green vegetables such as kale, collards, spinach, turnip greens and broccoli are the richest sources. Vegetable oils such as soybean and canola oil, and fermented foods like natto, also contain vitamin K. People on warfarin should keep their intake consistent.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: Vitamin K deficiency bleeding
- American Academy of Pediatrics: Policy statement on vitamin K and the newborn infant
- NIH Office of Dietary Supplements: Vitamin K fact sheet for health professionals
- MedlinePlus: Vitamin K
- Merck Manual: Vitamin K deficiency