Eli Lilly (NYSE:LLY) is taking the unusual step of asking people who took compounded versions of their drug tirzepatide, marketed as Zepbound for weight loss and Mounjaro for type 2 diabetes, for medical records to examine potential safety concerns.

Eli Lilly & Co. is asking people who took copies of its blockbuster weight loss drug to give the company access to their medical records as it continues to build a case against businesses selling the compounded drugs.

We recently learned that you took one of our products from a compounded pharmacy,” Lilly wrote in a letter viewed by Bloomberg News. “We would appreciate if you could complete the enclosed form and sign the Authorisation for Release of Medical Information so that we can obtain more details from the treating physician around your experience.