Pseudohyperkalemia can result from

Hyperkalemia should be distinguished from factitious hyperkalemia or "pseudohyperkalemia," an aifactual increase in serum K+ due to the release of K+ during or after venipuncture. Pseudohyperkalemia can occur in the setting of excessive muscle activity during venipuncture (e.g., fist clenching), a marked increase in cellular elements (thrombocytosis, leukocytosis, and/or erythrocytosis) within vitro efflux of K+, and acute anxiety during venipuncture with respiratory alkalosis and redistributive hyperkalemia. Cooling of blood following venipuncture is another cause, due to reduced cellular uptake; the converse is the increased uptake of K+ by cells at high ambient temperatures, leading to normal values for hyperkalemic patients and/or to spurious hypokalemia in normokalemic patients. Finally, there are multiple genetic subtypes of hereditary pseudohyperkalemia, caused by increases in the passive K+ permeability of erythrocytes. For example, mutations in the red cell anion exchanger (AE1, encoded by the SLC4A1 gene) Ref: Harrison 19e pg: 309