pironolactone is an androgen receptor antagonist that is an effective treatment for hormonally mediated acne. [1][2][3][4] Although generally well tolerated, spironolactone use is associated with hyperkalemia among patients with heart failure taking additional drugs that interfere with potassium excretion. 5 However, the prevalence of spironolactoneinduced hyperkalemia among young women taking spironolactone for acne is unclear. To date, there have been 4 small-scale clinical studies, 6-9 each fewer than 100 patients, that have measured serum potassium as a secondary outcome in patients taking spironolactone for acne. Three studies 6-8 yielded zero cases of hyperkalemia, and one study 9 showed a 13.7% rate of mild hyperkalemia, which was defined as a se-rum potassium measurement of 4.8 to 5.3 mEq/L (to convert potassium level to millimoles per liter, multiply by 1.0).Although the US Food and Drug Administration recommends frequent potassium monitoring in patients taking spironolactone, it is unclear whether this guideline is applicable to healthy patients taking spironolactone for acne. If the rate of hyperkalemia in this population is low and clinically insignificant, the cost of regular potassium monitoring may exceed the benefit of capturing these cases. In addition, concerns over hyperkalemia and frequent laboratory testing may contribute to health care spending and discourage the use of this effective drug. The objective of this retrospective study was to measure the rate of hyperkalemia in a large population IMPORTANCE Spironolactone has been shown to be an effective treatment option for hormonally mediated acne but can cause hyperkalemia. The prevalence of hyperkalemia among healthy young women taking spironolactone for acne is unclear.OBJECTIVE To measure the rate of hyperkalemia in healthy young women taking spironolactone for acne or for an endocrine disorder with associated acne.