Vitamin K deficiency is uncommon in healthy adults and is judged by a clearly longer clotting time. The main concern is vitamin K deficiency bleeding in newborns, because little vitamin K crosses the placenta and breast milk is low in it; US and Canadian pediatric societies recommend a vitamin K shot at birth to prevent it. In adults, deficiency mainly affects people with fat malabsorption or after bariatric surgery.
Common symptoms
Easy bruising and prolonged bleeding from minor cuts
Bleeding gums or frequent nosebleeds
Heavy menstrual bleeding
Blood in urine or stool (dark, tarry stools)
Internal bleeding, especially in the gut
In newborns: bleeding from the umbilical stump, skin, nose or gut, or into the brain
Signs of brain bleeding in infants, such as extreme sleepiness, pale skin, a bulging soft spot, vomiting or seizures, need emergency care
Long-term low status may reduce bone mineralization
At-risk groups
Newborns not given vitamin K at birth
Exclusively breastfed infants (breast milk is low in vitamin K)
People with fat malabsorption, such as cystic fibrosis, celiac disease, ulcerative colitis or short bowel syndrome
People who have had bariatric surgery
People on long courses of antibiotics with low vitamin K intake
People taking bile acid sequestrants or orlistat for long periods
When to see a doctorAny unexplained bleeding in a newborn, such as bleeding from the umbilical stump, blood in stool, vomiting blood, or signs of brain bleeding like extreme sleepiness or seizures, is an emergency and needs immediate care. In adults, unexplained easy bruising or bleeding is a reason to ask for a clotting test (PT/INR). If you take warfarin, do not start vitamin K supplements without your doctor's approval, because they change how the medicine works.