The major causes of hypokalaemia are gastrointestinal and renal losses of potassium. The clinical effects are mainly muscle weakness, cardiac arrhythmias and impaired kidney function. Hypokalaemia can be corrected with oral potassium-sparing diuretics. Oral potassium chloride is less effective and the number of tablets required is large. For example, each 600 mg tablet contains 8 mmol of potassium and replacement requires 40 to 60 mmol of potassium per day. It is difficult to administer sufficient potassium through diet alone, e.g. 2.5 cm of banana contains 1 mmol of potassium. Potassium is largely an intracellular cation and a 1 mmol/L reduction in serum potassium indicates a total body deficit of approximately 350 mmol.