Injectable peptides

What counts as an injectable peptide?

A peptide is any amino-acid chain of 40 or fewer, FDA's line between peptides and larger proteins [1]. Many FDA-approved peptide drugs are given by injection. Examples include Forteo (teriparatide), dosed at 20 mcg subcutaneously once a day [2], and Pregnyl, a polypeptide hormone from the human placenta given by injection [3]. Some approved peptides, like Wegovy, are also available as tablets. The term is a delivery method, not a claim about approval status, and it groups regulated medicines alongside products that have not been reviewed at all.

Why are unapproved peptides also sold as injectables?

Many peptides marketed online outside FDA approval, including research-use-only and compounded products, are also sold in injectable form. FDA has flagged this route specifically: reviewing one peptide nomination, the agency wrote that injectable routes of administration may present a particular risk for immunogenicity [4]. A research use only product and a compounded peptide are both legally distinct from an FDA-approved injectable peptide. Because these products are not FDA-approved, there is no label describing their risks the way Forteo's or Pregnyl's labels do.