Science first.
Then everything else.
Most of what's written about peptides online is marketing. We wanted a reference that tells you how strong the evidence is, including when it's weak.
For each compound we cover what it is, how it works step by step, what has been shown in people, in animals and in the lab, how it is used, what goes wrong and who should stay away. Every important claim carries a grade, so you can see at a glance whether it rests on a large human trial or a single mouse study.
The NexGen evidence scale
Two claims can sound identical and rest on completely different evidence. Every claim gets a letter grade and a confidence rating.
A regulator has approved it, and official prescribing information exists.
e.g. Tirzepatide for weight lossTested in people, from randomised trials down to small pharmacokinetic studies.
e.g. GHK-Cu on skin, SemaxPhysicians use it outside an approved label, based on clinical experience or indirect human data.
e.g. Clinic joint injectionsWidespread in fitness and longevity circles without controlled proof.
e.g. Ipamorelin stacksCell, animal or mechanism data only. Not yet shown in people.
e.g. BPC-157 tendon healingVery low → High
The grade tells you what kind of evidence exists. The dots tell you how good it is within that grade. One small human trial and ten large ones are both Grade B, but they don't deserve the same trust.
Published: what a trial actually used. Clinical: what physicians do off-label. Community: what circulates in practice. A community figure is never presented as a medical standard. Where no reliable figure exists, we say so instead of inventing one.
Peptides 101
Amino acids are the beads. A few of them strung together make a peptide. Hundreds make a protein.
A peptide is short enough to carry one clear instruction, and your body already runs on hundreds of them. Some tell the pancreas to release insulin, some tell the brain you've eaten, and some tell tissue to repair. Almost every compound in this guide works the same way: it carries a signal to a target, and the target changes what it does.
Receptors are locks. A peptide only affects cells that carry its matching receptor. An agonist turns the lock and switches a response on. An antagonist sits in the lock and blocks it. Once a receptor fires, a cascade inside the cell amplifies the message, which is how a microgram-scale dose can change a whole tissue.
Some act on enzymes instead. A few compounds, such as 5-Amino-1MQ, switch an enzyme on or off rather than binding a surface receptor.
Half-life sets the schedule. Native peptides are cleared within minutes to hours. Engineered ones like tirzepatide carry a fatty-acid tail that binds albumin, so one dose lasts about a week.
Why most are injected. Your gut breaks proteins down, so a swallowed peptide usually gets digested before it can act. A subcutaneous injection skips the gut. A few survive other routes: Semax and Selank are given in the nose, and BPC-157 is unusually stable in stomach acid.
The types you'll meet
| Type | Meaning | Example |
|---|---|---|
| Natural peptide | A copy of something your body already makes | GHK-Cu |
| Analogue | A natural peptide modified to last longer or act harder | Semaglutide |
| Secretagogue | Tells a gland to release more of its own hormone | Ipamorelin |
| Hormone | A complete signalling molecule | HGH, Oxytocin |
| Fragment | The useful piece cut from a larger protein | TB-500, AOD-9604 |
| Small molecule | Not a peptide, but used the same way | 5-Amino-1MQ |