It is legal to sell research only peptides that are not FDA approved, but as soon you talk about efficacy and human use, you also become a target for the FDA warning letters. [1] [2] [3].
Anyone selling these peptides who are indexed by search engines face increase scrutiny immediately, especially if you're going to try to sell the patented ones, because then you're a Target of not just the FDA but also Eli Lilly... peptides are big business but it's big risk if you do it wrong.... Eli Lily wants people spending $1,000 per month to use these peptides.
I think the trick about selling peptides to people is to probably do it word of mouth, no indexing by google, no ads, double gated website with invite only structure.
[0] https://www.npr.org/2026/08/13/g-s1-138594/eli-lilly-files-6...
[1] https://www.fda.gov/inspections-compliance-enforcement-and-c...
[2] https://www.fda.gov/inspections-compliance-enforcement-and-c...
[3] https://www.raps.org/resource/fda-warning-letters-target-mar...