Normal potassium in the presence of gross hemolysis.

A 15-year-old boy presented to the emergency department with acute development of fever and chills. Physical exam revealed a blood pressure of 86/61, jaundice with scleral icterus, and dark urine. Laboratory tests (increased free hemoglobin, increased lactate dehydrogenase, and decreased haptoglobin) revealed a direct antiglobulin test (DAT)negative hemolytic anemia. Sequential serum potassium measurements remained normal to low (reference interval, 3.6–5.2 mmol/L) through the majority of his disease course (Fig. 1).