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 check the evidence and the legal status before anything else. 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.
Everything you need, in one place
What the finder shows
Pick a goal and the finder shows two things. First, the approved medicines for that goal, where any exist: for weight management, semaglutide, tirzepatide and liraglutide, all prescription medicines;1,2 for growth hormone, the hormone itself for diagnosed deficiency and tesamorelin for one narrow use.3 Second, the research compounds people discuss for it, each with its regulatory status and the evidence level from our encyclopedia. For tissue repair, cognition, longevity and immune support, no peptide is FDA-approved, and the finder says so.
Where a result names an approved medicine, it gives that medicine's label dose, read from the current label; it gives no dose for anything unapproved, because no label sets one. The doses quoted are Wegovy's, Zepbound's and Saxenda's for weight management and EGRIFTA SV's and EGRIFTA WR's for tesamorelin, each from its current label.1,2,4,3,5 The other answers, about experience, injections and how much evidence you want, change only one thing: if you prefer to avoid needles, the result adds a note on whether any non-injected form exists.
Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What changed, and why
This guide used to end its quiz with a "Suggested Starting Protocol": BPC-157 at 250 mcg a day injected near the injury, CJC-1295 with ipamorelin at bedtime, Semax as a nasal spray, GHK-Cu under the skin, thymosin alpha-1 twice a week. None of those doses came from an approved label or a trial result; they were community conventions presented as a beginner's plan. The results also made claims no source supported, among them that CJC-1295 with ipamorelin was "the most widely prescribed peptide stack in clinical practice", and the category cards printed monthly search volumes with no stated source. Two substances on the lists, pentosan polysulfate and NAD+, are not peptides.
The old roadmap told readers they could "source research-grade peptides independently" and use our calculator "to determine your exact dosage". A calculator converts a dose into syringe units; it cannot tell anyone what dose is safe. The new roadmap starts with the evidence and the legal status, and ends with keeping records for a clinician.
How to read a result
Each research compound comes with its status in plain words. "FDA-approved, prescription only" means a label, a tested dose and a prescriber. "Not approved in the US" means another country approved it, and the result says which. "Development discontinued" means a company started trials and stopped. "Not approved anywhere" means no regulator has approved it for any use, whatever a seller's page says. The evidence level is the one on the compound's encyclopedia entry, where every study behind it is listed with what it measured and in whom.
A research compound's place on the list is not a recommendation; it is there because people ask about it. The compound explorer lets you filter every entry by status and evidence.
What a research-use vial can hide
When researchers bought semaglutide from online sellers without a prescription, the vials held 29% to 39% more than their labels said, and every one contained bacterial endotoxin.6 A "research use only" label does not change what a product is: in its August 2026 warning letters to five online peptide sellers, FDA said such labels did not outweigh websites that showed the products were meant for people.7 Our guide to certificates of analysis explains what a lab report can and cannot prove.
Common mistakes
Treating research-use wording as reassurance is the first. The second is taking doses from forums as if they had been tested; for most research peptides, no dose has been tested in people at all. The third is measuring: FDA has received reports of people taking several times their intended dose of a compounded GLP-1 medicine because a dose written in units or millilitres was read as milligrams.8 The fourth is combining compounds, which multiplies what nobody has tested. The fifth is leaving out a clinician, who can offer the approved options where they exist and check for interactions with everything else you take.
Sources
- Novo Nordisk. WEGOVY (semaglutide) injection and tablets, US prescribing information: indicated for chronic weight management; prescription only; dose escalation schedule. DailyMed version of June 30, 2026, read September 30, 2026.
- Eli Lilly and Company. ZEPBOUND (tirzepatide) injection, US prescribing information: indicated for chronic weight management; maintenance 5 mg, 10 mg or 15 mg weekly. DailyMed version of September 2, 2026, read September 30, 2026.
- Theratechnologies Inc. EGRIFTA SV (tesamorelin) for injection, US prescribing information: indicated for the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy. DailyMed, read September 30, 2026.
- Novo Nordisk. SAXENDA (liraglutide) injection, US prescribing information: section 2 (0.6 mg daily for one week, then weekly increases to the recommended 3 mg daily). DailyMed version 22, effective February 25, 2026, read September 30, 2026.
- Theratechnologies. EGRIFTA WR (tesamorelin) for injection, US prescribing information: section 2 (1.28 mg under the skin once daily; applies only to the 11.6 mg vial). DailyMed version 2, effective July 29, 2026, read September 30, 2026.
- Ashraf, A. R. et al. (2024). Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription: Market Surveillance, Content Analysis, and Product Purchase Evaluation Study. Journal of Medical Internet Research, 26, e65440. PMID: 39509151 · doi:10.2196/65440
- U.S. Food and Drug Administration. Warning Letter 733652 to NuScience Peptides LLC (August 24, 2026; posted September 1, 2026), one of five letters to online peptide sellers that day. Read September 30, 2026. FDA
- U.S. Food and Drug Administration. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products (July 26, 2024). Read September 30, 2026. FDA
This explainer describes how the tool works and what its numbers rest on. It is not medical advice and does not recommend any dose or product.