BACKGROUND Electrolyte imbalance is frequent in many situations, but severe hyperchloremia is markedly rare in the absence of renal impairment. We report a patient with preserved renal function who exhibited severe hyperchloremia and negative anion gap. CASE REPORT A 70-year-old female with preserved renal function presented with fatigue and impaired consciousness. Venous blood gas analysis was notable for a chloride level of 137 mEq/L and anion gap of -18.2 mEq/L. Careful history taking revealed that she had taken bromide-containing over-the-counter painkillers. Her symptoms and laboratory tests gradually improved after intravenous hydration and painkiller withdrawal. The serum level of bromide ions on admission was later found to be 4-times higher than that considered toxic. CONCLUSIONS It is important to recognize that hyperchloremia with a negative anion gap strongly suggests bromide intoxication, and that bromide intoxication can develop even in patients with preserved renal function. Careful history taking is essential to the diagnosis because some over-the-counter drugs that are widely available and a few prescription drugs contain bromides.