Background: Severe hyponatremia is rare when carbamezapine is used as a monotherapy. It acts by inappropriate anti-diuretic secretion. Here we present a case of female with severe asymptomatic hyponatremia. Case report: A 61 year female which was a known case of trigeminal neuralgia and hypertension presented to opd for her routine checkup. She was taking tab carbamezapine 300mg TDS, temisartan 40 mg and amlodipine 5 mg once a day. Her blood pressure was 126/82 mm of Hg, pulse rate was 72 bpm. Her systemic investigation was normal. Her baseline blood investigation was sent as a part of routine checkup and her sodium was reported to be 109 mEq/l. Her sodium was repeated again and was found to be 111 mEq/L. she was admitted in view of hyponatremia in the ward. Her serum osmolarity was 228 mosm/kg , urine sodium was 92 mEq/l, urine osmolarity was 306mOsm/kgH20, uric acid was 2.1 mg/dl. Tsh was normal. Our patient was diagnosed with SIADH . Her carbamezapine was stopped, salt intake was increased and fluid were restricted. 5 day after her sodium improved to 126 m Eq/l. she was discharged and on followup her sodium was 132m Eq/l after 1 week. Conclusion : hyponatremia is a life threatening condition and is multifactorial. acute hyponatremia is more symptomatic than chronic. Hence we should be very careful in managing these patients
