What Are Peptides?

The Basics

Peptides are short chains of amino acids — the same building blocks that make up proteins. Where proteins might be hundreds or thousands of amino acids long, peptides are typically just 2 to 50 amino acids. That small size is what makes them biologically active in specific, targeted ways.

Your body produces peptides naturally to regulate everything from hunger and sleep to tissue repair and immune function. The peptides studied in research today often mimic or enhance these natural signals.

How Peptides Work

Most peptides work by binding to specific receptors on cell surfaces, acting like keys that fit particular locks. When a peptide binds to its receptor, it triggers a cascade of signaling inside the cell — telling it to grow, repair, release a hormone, or change behavior in some way.

Because peptide-receptor interactions tend to be highly specific, peptides can produce targeted effects with potentially fewer off-target consequences than small-molecule drugs. That specificity is a big part of why peptide research has accelerated in the past decade.

Major Categories

How Peptides Are Administered

Because most peptides are broken down in the digestive tract, they can't typically be taken as a pill. The most common routes of administration in research are:

• Subcutaneous injection — the most common route. Small insulin syringes are used to deliver peptides just under the skin.
• Intramuscular injection — used for certain peptides that need deeper tissue absorption.
• Nasal spray — used for peptides targeting the brain, like Semax and Selank.
• Oral — only a few peptides survive digestion well enough for this route (e.g., BPC-157 in gut applications).

Reconstitution

Peptides are typically shipped as a freeze-dried (lyophilized) powder that needs to be mixed with sterile bacteriostatic water before use. The amount of water affects the concentration, which determines how much volume you'd draw for any given dose.

ThePBrief provides a reconstitution calculator for every peptide in our database. Select a peptide and you'll see visual guides for exactly how much water to add and how many units to draw for a given dose.