Background: Hyperkalemia is a potentially life-threatening medical condition; on the other hand pseudohyperkalemia is a benign entity, which should be suspected when serum potassium is elevated without concomitant electrolyte imbalances or remarkable degree of renal dysfunction. Patients seldom have the classical manifestations of hyperkalemia. Failure to recognize this condition causes anxiety among physicians, unnecessary laboratory testing and unwarranted treatments.
Case Report: We describe a sixty-year-old woman with persistent hyperkalemia and mean platelet count over a six-month period of 1015×103 cells/cumm. Based on this finding of thrombocytosis an immediate hematological evaluation has detected a myeloproliferative disorder, specifically essential thrombocythemia. Normalizing platelet count was paralleled by resolution of hyperkalemia.
Conclusions: Pseudohyperkalemia might be the tip of the iceberg to a major underlying pathological process. Unless a high index of suspicion to diagnose this disorder is maintained it will continue to be remarkably under diagnosed, subjecting patients to numerous unnecessary tests and treatments.

Keywords: pseudohyperkalemia, myeloproliferative disorder, essential thrombocytosis