Poor purity can cause patients to experience fever, chills, nausea, skin irritation, infections and low blood pressure.

Eli Lilly's weight-loss drug Zepbound and diabetes medication Mounjaro are no longer in short supply. That could limit cheaper copycat versions.

Zealand Pharma CEO Adam Steensberg said Friday that the company is working on a next-generation weight loss drug that’s designed to work differently from those currently on the market and with the potential for fewer side effects.

Peptide companies' are creating knock-off versions of these drugs that have not been approved by the FDA and contain ingredients that may lack the purity of the branded medications.