Hypernatremic dehydration secondary to lactation failure remains a potentially life-threatening condition in countries where advanced laboratory investigations are scarce. An 11-day term baby with excessive weight loss (33.6%), reduced urine output, fever, jaundice, doughy skin, opisthotonus posturing, and tachycardia with poor perfusion was presented to our neonatal care. The baby was diagnosed with shock with hypernatremic dehydration. An initial bolus of 20 ml/kg of N/S was repeated 3 times (each over 20 minutes), i.e., a total of 204 ml was given over 1 hr, until the vital signs were normalized to PR-145, RR-45, T-37.2°C, SPO2-100%, and CRT < 3 seconds, and the baby began to void urine. Free water deficit and sodium excess was managed by gradual and slow correction over 72 hours to prevent cerebral oedema and neurologic sequelae. The baby required reconstituted solutions of 5% D/W + 1/2 N/S at a rate of 27 ml/hr for 72 hrs. Sepsis and hyperbilirubinemia were treated with antibiotics and phototherapy. Management of symptomatic hypernatremic dehydration must be considered in settings with inadequate laboratory facilities.