Peptide Therapy · Reviewed by Ian K. Tseng, MD

What Are Peptides? A Plain-English Guide

Peptides are everywhere on your feed right now — in serums, in wellness podcasts, in "before you take these, know this" videos. Underneath the hype is a simple biology: a peptide is a short chain of amino acids that tells your cells what to do. Here is what that actually means, and where the marketing stops and the medicine begins.

Published July 8, 2026 · Medical review by Ian K. Tseng, MD, Medical Director

Peptides are the body's text messages

Every protein in your body is built from amino acids strung together like beads on a chain. When that chain is long — roughly 50 to 100 amino acids or more — scientists call it a protein. When it is short, they call it a peptide. That is the entire distinction: peptides are short, proteins are long. Chains of about 10 to 20 amino acids are sometimes called oligopeptides, and longer ones polypeptides, but the everyday rule of thumb holds.

What makes peptides interesting is not their size but their job. Many peptides act as signaling molecules — chemical messages that tell a specific type of cell to do a specific thing. Insulin, the hormone that manages your blood sugar, is a peptide 51 amino acids long. It was the first peptide ever synthesized in a lab, in 1921, and has been used to treat type 1 diabetes since 1923. Your body is quietly producing thousands of these messengers right now, regulating appetite, immune response, wound healing, and hormone rhythms.

Peptides vs. proteins vs. collagen — untangled

These three words get used interchangeably online, which causes a lot of confusion. Here is the clean version:

• Amino acids are the individual building blocks.
• Peptides are short chains of them.
• Proteins are long chains of them. Collagen — the protein that gives skin its structure and stretch — is one example.
• Collagen peptides (also called hydrolyzed collagen) are collagen that has been broken down into short fragments so your body can absorb them. That is why supplement powders use them instead of whole collagen.

So when a skincare label says "peptides" and a supplement tub says "collagen peptides," they are pointing at the same underlying chemistry — short amino-acid chains — used in very different ways.

The big split: cosmetic peptides vs. medical peptide therapy

This is the single most important thing to understand, because the two live in completely different worlds — different regulation, different oversight, different stakes.

Cosmetic (topical) peptides

These are ingredients formulated into creams and serums you buy over the counter and apply to the surface of your skin. Copper peptides (GHK-Cu) and Matrixyl (a synthetic peptide) are two you will see named on labels; they are marketed to support the skin's own collagen and elastin. Because they are cosmetics, they do not require a prescription and do not go through drug approval. Their claims are beauty claims, not medical ones.

Physician-supervised peptide therapy

This is a medical service, not a product you add to a cart. Our physician-supervised peptide therapy program works this way: a licensed physician evaluates your goals, health history, and bloodwork through a Good Faith Exam, and only then determines whether a prescribed protocol is appropriate. Programs are organized into categories of care — aesthetics and anti-aging, recovery and tissue repair, metabolic optimization, and performance and vitality — described by what they support in the body rather than by product names. Whether any specific therapy is right for you is a clinical decision, and not everyone qualifies.

The rule to carry with you: if someone is selling you a specific injectable peptide by name with a price and no exam, that is a red flag. We cover why in our companion article on whether peptides are safe.

Why the sudden hype?

Three things collided. First, the general public learned that a well-known class of metabolic medications are peptides, which pulled the word into everyday conversation. Second, skincare brands leaned into "peptide" as a hero ingredient. Third, social platforms reward dramatic claims, so "this peptide changed my life" and "this peptide is dangerous" both travel fast — often with more confidence than evidence. The biology is real and genuinely useful; the internet's version of it is a mix of real science, cosmetic marketing, and gray-market selling. Knowing which is which is the whole game.

Where to go next

• Topical vs. injectable peptides — why the delivery method changes everything.
• Are peptides safe? — the FDA status, buying online, and what "know before you start" really means.
• Why peptide therapy starts with bloodwork — the labs a physician reviews first.

Frequently asked questions

This article is educational and is not medical advice. Statements have not been evaluated by the FDA. Peptide therapy is a physician-supervised medical service; specific protocols are determined individually after a Good Faith Examination and bloodwork, and not all applicants qualify. Some compounded medications used in physician-prescribed protocols are not FDA-approved. Data from clinical trials on FDA-approved medications should not be used to make assessments related to compounded medications. Soothe IV's peptide program is available in California.