Federal regulators are tracking more than 1,700 reported problems involving compounded versions of the two best-known weight loss injections, according to a report from MedicalDaily, which notes the agency says the real number is almost certainly higher than what has been counted.

The drugs are compounded semaglutide (the active ingredient in Ozempic and Wegovy) and compounded tirzepatide (Mounjaro and Zepbound). Compounded means a pharmacy prepares the product for a patient whose needs an approved drug cannot meet, and it is not reviewed or approved by the FDA before reaching that patient, which is the distinction consumers most often miss.

What the numbers actually say

As of May 31, the agency had received 990 adverse event reports associated with compounded semaglutide and more than 730 associated with compounded tirzepatide. Those totals do not establish that the products caused every reported problem, and they are likely undercounts, because state-licensed pharmacies that are not outsourcing facilities are not required to file reports at all.

Separately, America's Poison Centers reports that poison centers managed 22,966 exposure cases involving this drug class from 2019 through 2025, and describes a nearly 1,500 percent rise in related calls since 2019. The organization cautions that its case records are self-reported and that annual data stay preliminary until locked.

The vial is the problem

The clearest pattern in the agency's reporting is measurement. Approved injectables arrive in prefilled pens calibrated to a set dose, while many compounded versions arrive as a multiple-dose vial and a syringe, which hands the arithmetic to the patient.

In the agency's dosing error alert, most reports described patients drawing up more than prescribed and administering five to 20 times the intended dose, with some requiring hospitalization. Clinicians made errors too: the agency describes providers miscalculating milligram-to-unit conversions and producing doses five to 10 times higher than intended.

Research use only is not a formality

Alongside the compounded market sits a less supervised one, with products sold as peptides for weight loss, muscle growth, and recovery, some labeled as never intended for human use. The agency has warned companies that sold unapproved drugs containing semaglutide, tirzepatide, retatrutide, survodutide, or mazdutide under that labeling while supplying consumers with dosing instructions.

Shabbir Imber Safdar of Partnerships for Safe Medicines told WBAY that consumers are misled by the assumption that advertised products must be legal, naming retatrutide among compounds he said cannot legally be distributed to Americans. Regulators agree: the agency states retatrutide and cagrilintide cannot be used in compounding, are not components of any approved drug, and have not been found safe and effective for any condition.

Bottom line

Adverse event reports record what someone experienced while using a product, not what the product did, and the agency says so directly. The unsettled part is regulatory: the agency has proposed excluding semaglutide, tirzepatide, and liraglutide from the bulk substances outsourcing facilities may compound with, and a final determination is still pending after the comment period closed in July.