Peptides sit at the intersection of biological plausibility, clinical promise, and aggressive commercialization—yet most lack FDA approval and rigorous safety data. Peter Atia provides a practical framework for evaluating gray-market peptides (SS-31, melanotan-II, CJC-1295, BPC-157) by examining mechanism of action, human efficacy evidence, safety profiles, and whether approved alternatives exist, helping you determine if any peptide warrants real-world use. A viable mechanism of action is essential for any drug evaluation; less than 3% of FDA-approved medications lack defined mechanistic pathways, and peptides without them should be viewed with extreme skepticism. Most popular gray-market peptides like BPC-157 lack replication in humans despite strong animal data, making efficacy claims speculative and risk-benefit analysis impossible without long-term safety studies.