Pseudohyperkalemia is a laboratory artifact that can show a clinically nonsignificant hyperkalemia due to a variety of causes, including hematologic abnormalities, errors in blood sample collection, and complications of serum potassium measurement. Rarely, pseudohyperkalemia can present in a familial form.

Hematologic abnormalities are a common cause of pseudohyperkalemia and include significant leukocytosis or thrombocytosis. Pseudohyperkalemia is also often due to errors in blood sample collection, such as potassium release secondary to a tourniquet or hemolysis within the test tube. Pseudohyperkalemia can be a complication of serum potassium measurement due to excess potassium release from the clot that forms during the separation of serum. Familial pseudohyperkalemia is caused by hereditary xerocytosis. This defect causes red cell membrane abnormalities that increase cellular potassium leak within collection tubes. Plasma potassium measurement, which is becoming more common, is not often affected by these spurious elevations.