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Buying counterfeit weight loss drugs from illegal online pharmacies that don't require prescriptions is, in fact, a very bad idea, according to a study published Friday in JAMA Network Open.

The counterfeit drugs are sold as equivalents to the blockbuster semaglutide drugs, Ozempic and Wegovy, which are prescription only. When researchers got their hands on three illegal versions, they found that the counterfeit drugs had low-purity semaglutide, had dosages that exceeded the labeled amount, and one had signs of bacterial contamination.

The three substandard drugs tested came from three different illegal online pharmacies, which sold them as generic semaglutide drugs for weight loss, appetite suppression, diabetes, and cardiovascular health. However, the researchers, led by scientists at the University of California, San Diego, and the University of Pécs in Hungary, had initially tried purchasing counterfeit drugs from six such sellers.