Everything You Need to Know
About Peptides
New to peptides? This guide covers the fundamentals — what they are, how they work, the major categories, and how to get started safely. No jargon. No assumptions. Start here.
What are peptides?
The 60-second explanation.
Peptides are short chains of amino acids — the same building blocks that make up proteins. While proteins can contain hundreds or thousands of amino acids, peptides are smaller, typically between 2 and 50 amino acids long.
Your body produces peptides naturally. They act as signaling molecules — messengers that tell your cells what to do. Different peptides trigger different biological responses: healing tissue, releasing hormones, fighting pathogens, regulating metabolism, and much more.
Therapeutic peptides are synthetic versions of these natural signals. By introducing specific peptides externally, researchers aim to amplify or restore biological processes that may be diminished by age, injury, or disease.
Peptide vs. Protein?
Size. Peptides are under ~50 amino acids; proteins are larger. Insulin (51 amino acids) sits right at the boundary.
Peptide vs. Steroid?
Completely different. Steroids are lipid-based hormones (testosterone, cortisol). Peptides are amino acid chains. Different chemistry, different mechanisms.
Are peptides natural?
Yes — your body produces hundreds of peptides. Therapeutic peptides are synthetic copies designed to mimic or enhance these natural signals.
Are peptides legal?
It depends on the specific peptide and your country. Some are FDA-approved prescription medications. Others are available as research chemicals. See our legality guide for details.
How do peptides work?
Peptides are signaling molecules. Here's the simplified version.
Administration
The peptide enters your body — usually via subcutaneous injection, intranasal spray, or oral capsule.
Receptor Binding
The peptide's amino acid sequence acts like a key, binding to specific receptors on target cells throughout your body.
Signal Cascade
Binding triggers an intracellular signaling cascade — a chain reaction of biochemical events inside the cell.
Biological Response
The cascade produces the therapeutic effect: tissue repair, hormone release, immune activation, gene expression changes, etc.
The 6 major peptide categories
Peptides are organized by their primary therapeutic application. Each category contains multiple compounds.
Peptide Finder Quiz
Answer 4 questions and get a personalized recommendation for where to start.
Getting started: 6-step roadmap
Follow this sequence whether you're exploring for the first time or ready to begin.
Important safety considerations
Peptides are not FDA-approved drugs
With few exceptions (semaglutide, tirzepatide, PT-141), most peptides discussed here are not FDA-approved for therapeutic use. They are used off-label or as research chemicals.
Quality varies dramatically
The peptide market includes everything from pharmaceutical-grade compounds to untested products. Always verify third-party Certificates of Analysis (COA) showing purity and identity testing.
Medical supervision matters
Peptide therapy should ideally be supervised by a licensed healthcare professional who can order appropriate bloodwork, monitor for side effects, and adjust protocols.
More is not always better
Peptides work through receptor signaling. Excessive dosing can cause receptor desensitization (downregulation), making the peptide less effective over time. Follow established protocols.
Sterile technique is non-negotiable
Contamination during reconstitution or injection can cause infection. Follow the procedures in our Mixing Guide. If a solution looks cloudy, discolored, or has particles — discard it.
Know your contraindications
Many peptides have specific contraindications (active cancer, pregnancy, certain medications). Review the safety section of each peptide's Encyclopedia entry and discuss with your provider.