A 15-minute plain-English read that defines every word it uses. If you already know this material, skim the bold lines and the last section.
This guide teaches you to read and reason about peptides the way people who work with them actually do: what the names mean, how to weigh the evidence behind a claim, and how to tell research from marketing. It was written for motivated readers with no science background — but the field still talks about molecules and cells, so this guide gets you the vocabulary first.
Nothing here asks you to memorize. Read it once, know that it exists, and come back when a word stops you.
Your body is built and run by proteins — big molecules that do jobs: carry oxygen, fight infections, send signals. (A molecule is any chemical built from atoms joined in one specific arrangement — a drop of water is a molecule, and so is the DNA in a cell. It's the general word for "a chemical thing with a definite shape," and that's the only sense we'll use it in.)
Every protein is a chain of smaller units called amino acids. There are 20 standard kinds, and you can think of them as an alphabet:
The word "peptide" doesn't describe one thing with one job. It describes a size class of molecule: small enough to make in a lab cheaply, big enough to be astonishingly specific about what it attaches to. That combination is why there's a whole industry around them.
Two real examples, so this isn't abstract:
The links that join amino acids into a chain are called peptide bonds — that's where the name comes from. For now, "chain of letters" is all you need.
One more word: "sequence." The order of amino acids in a chain. Change the order and you change the molecule entirely — the same way rearranging letters turns "silent" into "listen." When people write a peptide's sequence, they write it in a standard direction, start-to-end, like reading left to right.
Almost every idea in this guide is built on five words. Here they are in kitchen English.
Cell. The basic unit of life. Your body is ~30 trillion of them. Everything a peptide does, it does to or around cells.
Receptor. A molecule on the outside of a cell shaped so that exactly one kind of signal fits it — like a socket that only takes one plug. When the right molecule plugs in, the receptor passes a message into the cell: "do this." Cells have thousands of receptors each, of hundreds of kinds. Nearly every peptide medicine works by plugging one specific receptor.
Agonist / antagonist. Two flavors of plug. An agonist plugs a receptor and switches it on — it tells the cell to do the thing. An antagonist plugs the same receptor and blocks it — nothing else can plug in, so the message never gets sent. Semaglutide is an agonist (it switches on the "you're full" signal). Many overdose antidotes are antagonists.
Enzyme. A molecule whose job is performing one chemical task over and over — cutting, joining, copying. The enzymes that matter most here are proteases: enzymes whose job is chopping peptides and proteins into pieces. Your stomach and blood are full of them. This is the villain of the whole peptide story — peptides get chopped up, which is why they mostly can't survive as pills and wear off quickly. Almost every design trick you'll learn exists to outsmart a protease.
Half-life. How long until half of the molecule is gone — cleaned up, chopped up, filtered out by the kidneys. A peptide with a 10-minute half-life is mostly gone in an hour and would need dosing many times a day. Drug designers spend enormous effort stretching short half-lives into long ones. When you read "half-life extension" anywhere, read "making it last longer."
This one fact explains half of everything in the peptide world.
Your digestive system treats anything protein-or-peptide-shaped as food. That's literally its job — stomach acid and protease enzymes break the food you eat into amino acids before absorbing them. A swallowed peptide arrives at the stomach as a promising medicine and leaves as soup. It never reaches your bloodstream intact.
So most peptides are injected — a small needle puts them straight into tissue or blood, past the digestive system entirely. You'll see the word "bioavailability" along the way: it just means the fraction of the dose that actually reaches your bloodstream alive. Injected: high. Swallowed: usually zero.
(There are exceptions — engineered ways to sneak a peptide past the stomach. The best-known one is oral semaglutide. Notice what it took: a co-formulated helper molecule, ~1% bioavailability, and strict rules about taking it on an empty stomach. The exception proves how hard the problem is.)
Peptide names look like code because they are code — and the code is learnable. Three layers:
The ending tells you the family. Drug names are assigned stems by the WHO's INN system (international nonproprietary names — the generic name of a drug):
| Ending | Means | Example |
|---|---|---|
| -tide | a peptide (generic flag) | octreotide |
| -relin | triggers release of a hormone | tesamorelin, ipamorelin |
| -glutide | imitates the GLP-1 gut hormone | semaglutide, dulaglutide |
| -relix | blocks release of a hormone | cetrorelix |
Just from an ending you can often tell what a molecule is and roughly what it does, before reading anything else. There are more of these stems — once you know the pattern, you'll start recognizing them on sight.
Prefixes and suffixes tell you what was modified. A lab-modified peptide carries its modifications in its name, like a car's trim badge:
Real names use these badges, and you can read them the first try:
You are not expected to produce this notation. You're learning to read it: the goal is that a name like "desmopressin (dDAVP)" stops being noise and starts being a sentence.
The short names are nicknames, and nicknames lie. "BPC-157," "TB-500," "CJC-1295" are catalog nicknames, not scientific names. Sometimes one nickname covers two different molecules, and vendors don't always say which one they mean. This is a running theme — part of reading like an insider is knowing when a name is not answering your question.
You will see peptides for sale online labeled "for research use only." Understand precisely what that does and doesn't mean:
None of this is a recommendation to buy or use anything. This program is about understanding — reading claims, evidence, and marketing correctly. What you do with that understanding is outside its scope.
A claim is any statement of fact: "BPC-157 accelerates tendon healing." A source is where the claim came from: a clinical trial, a rat study, a forum post, a vendor's sales page.
The whole game is noticing that these are different things, and asking of every claim: says who, and how would they know? A few starting heuristics, in descending order of trustworthiness:
Every page on this site links each claim to its source, so you can always check yourself — that's the standard this site holds itself to — follow the links and check for yourself.
Want to keep going — from the basics to a genuinely professional understanding of peptides?
The Peptide Fundamentals Program is coming soon: a full structured course that builds on everything in this intro — the design tricks, the evidence reading, the naming, worked through real examples with practice questions and flashcards. Watch for it.
If you want to put this intro to work right now, pick any peptide on this site and read its page the new way: the name decoded, the claims tied to their sources, the marketing separated from the evidence. That's the whole skill.
The most-used peptide combinations, what the research actually says, and where to buy — one page, one email.
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