Subdural hematoma is a critical medical condition where blood accumulates between the layers surrounding the brain, posing severe risks due to pressure on brain tissues. Factors such as age, head trauma, use of anticoagulant medications like Nicoumalone (Acenocoumarol), and alcohol consumption elevate the likelihood of developing subdural hematoma. Clinical symptoms include intense headaches, difficulty swallowing, hoarseness, confusion, or excessive drowsiness. This case study involves a 60-year-old female patient admitted to a tertiary care hospital presenting with complaints of headache and vomiting. The patient had a medical history of rheumatic heart disease status post mitral valve replacement in 1996, atrial fibrillation with cardiovascular risk, hypertension, and dyslipidemia, all managed under ongoing treatment. Due to inadequate monitoring and prolonged administration of T.NICOUMALONE 3mg, the patient developed a subdural hematoma over time.