The Food and Drug Administration is warning people to be on the lookout for counterfeit Ozempic, the diabetes drug that many people use off-label for weight loss.

The federal agency and Novo Nordisk, the Danish pharmaceutical giant that makes Ozempic, said this week that they had learned about “several hundred units” of the drug that made it onto the market outside of the company’s approved supply chain.

Ozempic, made by Novo Nordisk, is part of a class of drugs known as GLP-1 agonists. The drugs are used to treat type 2 diabetes and obesity.