In the laboratory, a biochemical blood test was performed on an outpatient female patient who was being treated with diuretics. Serum potassium concentration was found to be 6.7 mmol/L (normal range 3.5-5.1 mmol/L). There was no visible hemolysis, and the blood was drawn immediately before the analysis.
The patient was asked to bring all her medications. It turned out that she was initially prescribed a loop diuretic (furosemide) and a potassium supplement for the treatment of congestive heart failure. However, during subsequent visits, spironolactone, a potassium-sparing diuretic (unlike furosemide) and an aldosterone antagonist, was prescribed instead of potassium. The patient misunderstood the instructions and continued to take the diuretic along with the potassium supplement. One week after discontinuing potassium intake, her serum potassium concentration normalized. Source: J. Marshall - Clinical Biochemistry, 2001
