HomeDeficienciesVitamin K deficiency

Vitamin K deficiency

Symptoms, at-risk groups, and clinical context for vitamin k deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.

→ See full Vitamin K profile

Vitamin K deficiency is uncommon in healthy adults because gut bacteria produce some K2 and small amounts are stored in tissues. The main concern is VITAMIN K DEFICIENCY BLEEDING (VKDB) IN NEWBORNS — a potentially fatal condition. All US newborns receive a vitamin K injection at birth to prevent it. In adults, deficiency primarily affects people on long-term antibiotics, those with severe fat malabsorption, or warfarin users.

Common symptoms

  • Easy bruising and prolonged bleeding from minor cuts
  • Bleeding gums, frequent nosebleeds
  • Heavy menstrual bleeding
  • Blood in urine or stool (dark, tarry stools)
  • Internal bleeding — especially gastrointestinal
  • In newborns with VKDB: bleeding from the umbilical stump, mucous membranes, GI tract, or — most seriously — into the brain (intracranial hemorrhage)
  • Signs of internal bleeding in infants: extreme sleepiness, pale skin, bulging fontanelle, vomiting, seizures (MEDICAL EMERGENCY)
  • Increased risk of bone fractures (chronic deficiency affects bone metabolism via osteocalcin)

At-risk groups

  • Newborns who do not receive prophylactic vitamin K injection at birth
  • Exclusively breastfed infants (breast milk is low in vitamin K)
  • Infants with cholestatic liver disease, biliary atresia, or cystic fibrosis
  • People taking warfarin or other vitamin K antagonists (intentional, requires monitoring)
  • People on long-term broad-spectrum antibiotics (alters gut flora)
  • People with severe fat malabsorption (Crohn's, celiac, short-bowel syndrome)
  • People with chronic liver disease
  • People who've had bariatric surgery
When to see a doctor: Any unexplained bleeding in a newborn — bleeding from the umbilical stump, blood in stool, vomiting blood, or signs of brain bleeding (extreme sleepiness, seizures) — is a MEDICAL EMERGENCY requiring immediate ER care. In adults, unexplained easy bruising or bleeding warrants a coagulation panel (PT/INR). Do NOT take vitamin K supplements if you are on warfarin without your doctor's approval — it can dangerously alter your medication's effect.
Sources: NIH ODS — Vitamin K Health Professional Fact Sheet · Hemorrhagic Disease of Newborn — StatPearls (NBK558994)
← All deficiencies

Related deficiencies

Nutrients with overlapping symptoms — useful when investigating an unclear clinical picture.

Vitamin B6 (Pyridoxine)FolateVitamin CZincPhosphorus / PhosphateRiboflavin