Japan warns of off‑label weight‑loss use of diabetes drug Mounjaro

Mounjaro, a medication approved in Japan in 2023 for type‑2 diabetes, has become popular for off‑label weight‑loss use. Health‑tech firm YourPill cautions that combining Mounjaro with low‑dose oral contraceptives can diminish contraceptive effectiveness, increasing the risk of unintended pregnancy. The drug slows gastric emptying, which can impair pill absorption, especially during the initial treatment period or after dose increases.

Reports also show that some psychiatrists and cosmetic clinics are prescribing Mounjaro to patients seeking to lose weight, despite no evidence of safety or efficacy for this indication. Medical professionals warn that such use may exacerbate eating disorders and cause severe nutritional deficits. Japan’s Ministry of Health, Labour and Welfare has issued notices to healthcare facilities urging proper use of the drug, and professional societies have joined the call for caution.