Eli Lilly publicly urged regulatory action after internal testing found an impurity forming when tirzepatide (the active ingredient in Zepbound/Mounjaro) was combined with vitamin B12 in compounded, ‘personalized’ formulations. Lilly warned the impurity’s short- and long-term human effects are unknown and asked the FDA to recall compounded tirzepatide products containing vitamins or supplements. The company’s move follows broader industry disputes over compounded GLP‑1 copies and comes as the FDA has signaled plans to crack down on compounding pharmacies marketing copycat metabolic drugs. Regulators and telehealth companies will now face pressure to reconcile access, safety and enforcement.