To the Editor: Agarwal and colleagues (Dec. 30 issue)(1) report the findings from a trial evaluating the use of chlorthalidone as an antihypertensive agent in patients with advanced chronic kidney disease (CKD) and poorly controlled hypertension. Although the findings show the potential of chlorthalidone as a valuable add-on therapy for poorly controlled hypertension, the article lacks the necessary discussion of common and potentially harmful side effects of thiazide diuretics. In a recent cross-sectional analysis conducted in Switzerland, we showed that approximately one in five patients receiving a thiazide diuretic presented with hyponatremia or hypokalemia.(2) Chlorthalidone was the thiazide diuretic with . . .