The short version: a peptide is a short chain of amino acids
— a tiny protein. Anabolic steroids (ring-shaped hormones) and SARMs (small synthetic
molecules) are not peptides. The GLP-1 family — semaglutide, tirzepatide,
retatrutide — are peptides. It matters because whether something is a peptide
changes how it's stored, how it's taken and how you'd track it.
These words get used loosely, and a lot of "peptide" lists quietly mix in things
that aren't peptides at all. Here's the clean version.
The four groups people muddle
Peptides — short amino-acid chains (BPC-157, the GLP-1s, growth-hormone
peptides). Usually a lyophilised powder you reconstitute and keep cold.
Anabolic steroids — hormones built on a four-ring structure (testosterone
and relatives). Chemically nothing like a peptide.
SARMs — selective androgen receptor modulators; small synthetic molecules,
often oral. Not peptides.
Other small molecules & coenzymes — things like MK-677 or NAD+ that
travel in the same conversations but aren't peptides.
Quick reference
Compound
Peptide?
What it actually is
Tirzepatide
Yes
GLP-1/GIP peptide
Semaglutide
Yes
GLP-1 peptide
Retatrutide
Yes
GLP-1/GIP/glucagon peptide
BPC-157
Yes
Short amino-acid chain
MK-677 (ibutamoren)
No
Oral small-molecule secretagogue
SARMs (e.g. RAD-140)
No
Small synthetic molecules
Testosterone
No
Anabolic steroid hormone
NAD+
No
Coenzyme, not amino-acid chain
Why the distinction is practical, not pedantic
Storage. Peptides are usually reconstituted and kept cold; oral small
molecules typically sit at room temperature. See
do peptides need refrigerating.
Form. A powder-in-a-vial that you mix behaves very differently from a
capsule.
Tracking. Knowing what a thing is keeps your records honest — the library
groups everything by what it actually is, not by marketing labels.
Common questions
Is semaglutide the same kind of thing as tirzepatide?
Both are peptides in the GLP-1 family; tirzepatide also acts on the GIP receptor. You can see
them side by side on the comparison page.
Are "research peptides" a different category?
No — "research use only" is a labelling status, not a chemical class. A research-labelled vial
of a peptide is still a peptide. See how to read a
vial label.
Why do some lists call MK-677 a peptide?
Loose usage. It's a small molecule, not an amino-acid chain — which is also why it's taken
orally rather than reconstituted.