503B outsourcing facilities are FDA-registered compounding pharmacies that can produce drugs without individual prescriptions, under more oversight than traditional compounding pharmacies (503A). They must follow current Good Manufacturing Practices (cGMP) and submit to FDA inspections. The FDA's crackdown on compounded semaglutide and tirzepatide has centered on 503A pharmacies and the question of whether these drugs are still in "shortage." When shortage status ends, 503A pharmacies may lose the ability to compound them, which is one reason people turn to the gray market.