Common questions about peptides — what they are, how they work, how they’re used, and how the legal landscape around them actually works. For compound-specific answers, check the directory.
Peptides are short chains of amino acids (typically 2-50) linked by peptide bonds. They are smaller than proteins and serve as signaling molecules in the body, acting as hormones, neurotransmitters, growth factors, and antimicrobials. Peptides are naturally produced by the body, and synthetic versions are used in research and medicine.
The main difference is size: peptides typically contain 2-50 amino acids, while proteins contain 50 or more. Proteins have complex three-dimensional structures, while most peptides are simpler chains. Functionally, peptides often act as signaling molecules, while proteins serve structural and enzymatic roles.
It depends on the specific peptide and jurisdiction. Some peptides are FDA-approved prescription drugs (semaglutide, tirzepatide, bremelanotide). Others are classified as research chemicals. Some are under FDA reclassification review. Always check the legal status of a specific peptide in your jurisdiction.
The most common route is subcutaneous injection using insulin-type needles. Some peptides can be taken nasally (Selank, Semax), orally (BPC-157, KPV, some GLP-1 agonists), or topically (GHK-Cu). The route depends on bioavailability — most peptides are degraded by stomach acid, which is why injection is preferred.
GHRPs (Growth Hormone Releasing Peptides) like Ipamorelin and Hexarelin stimulate GH release by activating the ghrelin receptor. GHRH analogs like CJC-1295 and Sermorelin stimulate GH release by activating the GHRH receptor. They work through different mechanisms and are often stacked together for synergistic effects.
Cycling refers to using a peptide for a defined period followed by a break. For example, 8 weeks on, 4 weeks off. Cycling prevents receptor desensitization, maintains effectiveness, and allows the body to restore natural function.
Lyophilized peptides should be stored frozen or refrigerated (2-8 C) and protected from light. Once reconstituted with bacteriostatic water, they should be refrigerated and used within 3-4 weeks. Never freeze reconstituted peptides.
Reconstitution is dissolving lyophilized peptide powder in bacteriostatic water. The water is slowly added and gently swirled (never shaken) to dissolve the powder. The amount of water determines the concentration.
GLP-1 agonists are peptides that mimic glucagon-like peptide-1, a natural hormone regulating appetite and blood sugar. They include semaglutide, tirzepatide, and liraglutide. They are FDA-approved for type 2 diabetes and obesity.
Side effects vary by class. GLP-1 agonists commonly cause nausea and GI issues. GH-releasing peptides may cause water retention and numbness. Melanotan II causes nausea and mole changes. BPC-157 and TB-500 are generally well-tolerated. Always start with lower doses.
A compounding pharmacy creates customized medications. 503A pharmacies fill individual prescriptions. 503B outsourcing facilities produce larger batches under FDA oversight. They are an important source for peptides not commercially available as branded products.
The FDA is reviewing certain peptides for potential reclassification. If reclassified, these peptides could return to legal compounding status through licensed pharmacies. As of 2026, no formal rule has been published.
Most peptides have poor oral bioavailability due to stomach acid degradation. Exceptions include semaglutide (Rybelsus, with an absorption enhancer), BPC-157 (GI effects when oral), KPV (efficacy in IBD models), and Dihexa. For most peptides, injection is necessary.
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