Frequently asked questions
Five questions on what Peptide Intelligence covers, how the comparison is built, and who it serves.
What peptides do you cover, and why aren't FDA-approved drugs in the catalog?
The catalog tracks research-grade peptides actively sold by the vendors we cover. Compounds approved by the FDA as drugs — semaglutide, tirzepatide, and similar — are deliberately out of scope. The consumer surface for those is the pharmacy and insurance system, not gray-market vendor comparison, and we have nothing useful to add there.
Catalog entries can be archived when both the evidence base and vendor coverage fall below threshold. A recent batch archived several Khavinson-family tetrapeptides and other low-coverage compounds on those grounds. The Khavinson Bioregulators category itself remains active for entries like Epitalon that are widely studied and widely stocked. Archived entries can return if either condition improves.
Why do you only compare four vendors?
Four vendors is enough depth to compare price-per-mg and trust signals across the same product without the analysis collapsing into thin coverage of dozens of sites. The current four are listed in the vendor directory.
Selection criteria: ships to the US, publishes a public catalog, has operated long enough to be reviewable, and makes some form of Certificate of Analysis available — even when imperfect. What would expand the list: another vendor that meets those criteria and adds consistent in-stock cadence plus clear shipping and return policy. Affiliate availability is explicitly not a criterion. We continue to list vendors we have no affiliate relationship with.
See the vendor directory for the current list.
What do T1, T2, T3, and T4 mean?
Quantitative claims on the site — half-life and Tmax in the dosing visualizer, stability windows in the stability reference — carry a tier label showing how strong the underlying source is. Briefly: T1 is peer-reviewed primary literature, T2 is regulator-reviewed drug labels (FDA approved drug labels and equivalents), T3 is manufacturer Certificate of Analysis or lab data, and T4 is applied USP/ICH or class-level standards used as a fallback when no compound-specific source exists.
The full convention and the reason it exists are documented on the methodology page under Source tiers.
See Source tiers on the methodology page.
How do I suggest a peptide or flag bad data?
The contact page routes everything to a single inbox. For a new peptide, the Vendor listing request card or a plain Corrections message both work — what helps is a PubMed PMID or two for the evidence base and one or more vendor URLs for the coverage signal.
For a data error — a stale price, a wrong dose unit, a broken link — the Corrections card with the URL and what should change is enough. We do not take requests framed in a treatment context: we will not endorse a peptide for a condition, debate a protocol, or weigh in on a personal regimen.
Go to the contact page to send a message.
Who is this site for, and who is it not for?
For: researchers, scientifically literate self-experimenters, and harm-reduction-minded buyers comparing vendors on price-per-mg, stock, and testing transparency. The audience model is someone who can read a research summary, look at a Certificate of Analysis, and make their own call.
Not for: patients seeking medical advice, anyone wanting a dose or a protocol, anyone seeking a vendor endorsement. We do not prescribe, recommend, or evaluate fit for any individual. Peptides discussed on the site are research compounds. If you are seeking treatment for a condition, talk to a clinician.