Clinical inquiries. How soon should serum potassium levels be monitored for patients started on diuretics?

Case series show that hypokalemia following initiation of diuretic therapy occurs in most patients within 2 to 8 weeks. However, no studies are available that adequately predict the risk of this complex and multifactorial condition. Patients taking diuretics should have a potassium level checked in the first 2 to 8 weeks after initiating therapy. Mild hypokalemia (3.1 to 3.4 mmol/L) may be transient, so a repeat measurement may be considered before initiating potassium replacement. Dietary sodium restriction may also help to conserve potassium, because this will decrease urinary flow rate and potassium loss. The frequency with which to check potassium levels should be guided by the patients’ underlying clinical conditions and dietary potassium and sodium intake. (Grade of Recommendation: C, based on case series)