The presence of only slightly visible hemolysis will significantly increase the serum level of which electrolyte?

• A. Sodium
• B. Potassium
• C. Chloride
• D. Bicarbonate

Answer: (B)

Hemolysis releases the contents of red blood cells into the serum. Red blood cells have a high concentration of potassium inside them, while the serum potassium is normally much lower. When even a small amount of rupture occurs, a relatively large amount of potassium pours into the serum, raising its measured level. Sodium, chloride, and bicarbonate are more characteristic of extracellular balance, and their intracellular concentrations are not as dramatically different from plasma levels, so they don’t show the same rise with slight hemolysis. In short, potassium is the electrolyte most affected by hemolysis, making pseudohyperkalemia a common pre‑analytical artifact.