What's the difference between research-grade and pharmacy-compounded peptides?

It comes down to who makes them and under what rules. Research-grade peptides (sold as "research use only" or "not for human consumption") are lab chemicals. Nothing requires them to be tested for sterility, endotoxins, or potency, and no prescription is involved. Per the FDA, that RUO label lets a supplier sell for lab or animal work; it does not authorize human use. Compounded peptides are made by a licensed pharmacy under section 503A, or a 503B outsourcing facility, of the Federal Food, Drug, and Cosmetic Act. They need a prescription and follow USP sterile standards (USP <797>, sterility per <71>). The ingredient also has to be eligible: the FDA's advisory committee put several peptides, including BPC-157, in Category 2 in 2023 over immunogenicity and impurity concerns, so 503A pharmacies can't compound those for people. Neither is FDA-approved. Whether a peptide fits you is a question for a licensed prescriber.