Andarine (S4) is a selective androgen receptor modulator (SARM) that can increase muscle mass and bone density without negative androgenic side effects like traditional anabolic steroids. Studies showed S4 was well-tolerated at doses up to 22mg daily for 14 days, resulting in increased lean body mass, decreased fat mass, and improved strength and well-being. As a SARM, S4 is orally bioavailable and a partial agonist of androgen receptors, allowing it to selectively target muscles and bones over sex organs. It can thus help with muscle growth and fat loss while cutting or bulking.