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Peptides 101
What peptides are and what they do, in plain English.
What’s a peptide?
A peptide is a tiny string of building blocks called amino acids. They’re the same building blocks that make up the protein in the food you eat.
Think of each bead as one building block.
A short string = a peptide. A really long string = a protein.
Your body already makes thousands of peptides on its own. Insulin — the one that helps control blood sugar — is a peptide you’ve probably heard of.
What do they do?
Most peptides work like text messages inside the body.
One part of the body sends out a peptide.
It travels to the cells it’s meant for.
Those cells “read” it and do a job — like repair, use energy, or signal “I’m full.”
Each peptide carries a different message. That’s why they’re studied — to learn how the body heals, uses energy, handles hunger, and ages.
Want it all on one page?
Our one-page cheat sheet lists every peptide by what it’s studied for. Easy to save or print.
Get the one-page cheat sheet (PDF)The most popular peptides, in one sentence each
Grouped by what they’re studied for. Tap any one to learn more.
Healing & recovery
Studied to learn how the body fixes tendons, muscles and the stomach lining.
Learn →·Usage →Weight & appetite
A copy of a natural “I’m full” message. Studied in weight-loss and blood-sugar research.
Learn →·Usage →Skin & rebuilding
Found naturally in the body. Studied for skin and collagen — the stuff that keeps skin firm.
Learn →·Usage →Energy & aging
Growth hormone
Words to know
Common words you’ll see on our site and around peptides, in plain English.
Peptide calculator →- Amino acid
- The tiny building blocks peptides are made of — the “beads” on the string.
- COA
- The lab’s report card for a batch.
- Purity (99%)
- How much of the vial is the peptide itself — 99% means almost nothing else is in there.
- mg
- Milligrams — how much peptide is in the vial.
- Lyophilized
- Freeze-dried. The peptide comes as a small puck of dry powder.
- Vial
- The small glass bottle the peptide comes in.
- Batch / lot number
- The code for one production run. It matches the vial to its lab report.
- Receptor
- The “mailbox” on a cell. A peptide’s message only works on cells that have the right mailbox.
- GLP-1
- A natural “I’m full” message your gut sends after you eat. Semaglutide, tirzepatide and retatrutide all copy it.
- HPLC
- The lab test that measures purity. It separates everything in the sample so the lab can see what’s there.
- Blend (or “stack”)
- Two or more peptides combined in one vial — like BB, GLOW and KLOW.
- Research use only
- Sold for laboratory research — not for people or animals to use.
How do I know it’s the real thing?
Every batch we sell is tested by an independent lab — not us.
The lab sends back a report called a COA (Certificate of Analysis). Think of it as a report card: it shows what’s in the vial and how pure it is. We post every one online, so you can check before you buy.
Still have questions?
We’re real people and we’re happy to help.
All Midwest Compounds products are for research use only. Not for human or animal use.