BACKGROUND AND OBJECTIVE: One of the most essential vitamins for body is vitamin 12B; its deficiency can cause various sign and symptom in the human body. Psychiatric manifestation of vitamin 12B deficiency including: aggression and agitation, is often accompanied by symptoms such as irritability and confusion, impaired orientation, amnesia, impaired concentration and attention, insomnia, anorexia and Negativism. Vitamin 12B deficiency may cause irreversible effects on the brain structure and it’s very important to early diagnose and treatment.

CASE REPORT: A Middle-aged man with psychiatric manifestations include: restlessness, nightmares, hallucinations, including seeing the scene of the fire in his home and the forest area around the house, auditory hallucinations and delusional beliefs with depressed mood, suicidal ideas, insomnia and anorexia who confer to neurologist office then refer to psychiatrist after mental status examination and laboratory study result show that vitamin 12B deficiency, other evaluations such as endoscopy and colonoscopy were normal then the patient gone under treatment by administration  intramuscular vitamin 12B supplemental and psychiatric manifestations improved dramatically after treatment.

CONCLUSION: This case report showed that psychiatric manifestations of vitamin 12B deficiency can occur even in the absence of anemia.