The Peptide Encyclopedia

Peptides are short chains of amino acids — the building blocks of proteins. Unlike full proteins, peptides are small enough to be absorbed and used as signaling molecules. They act as messengers, triggering specific biological processes such as hormone release, tissue repair, immune modulation, and fat metabolism. Hundreds of peptides occur naturally in the human body; synthetic versions mimic or amplify these effects.

FDA-approved peptides (e.g., semaglutide, tirzepatide, sermorelin) are legal by prescription in the United States. Research-grade peptides exist in a legal gray zone: they can be purchased for laboratory research purposes in most US states, but administering them to humans without a prescription is technically off-label. Laws vary internationally. Always consult a physician and understand local regulations before use.

Administration varies by compound. Most peptides are injected subcutaneously (under the skin) because they degrade in the digestive tract. Exceptions include: nasal sprays (Semax, Selank), oral tablets (Semaglutide as Rybelsus — specially formulated), topical creams (GHK-Cu, copper peptides for skin), and intravenous infusions (Cerebrolysin). Route of administration significantly affects bioavailability and onset.

BPC-157 and semaglutide (Ozempic/Wegovy) are the two most searched peptides globally. BPC-157 dominates the healing and recovery community — it has shown remarkable tissue repair properties in animal studies. Semaglutide leads the weight-loss space with FDA approval and massive clinical trial evidence (14.9% mean weight loss in STEP 1). Among growth hormone peptides, the CJC-1295/Ipamorelin stack is the most commonly used combination.

Yes — all peptides can have side effects. GLP-1 agonists (semaglutide, tirzepatide, retatrutide) commonly cause nausea (20–46%), diarrhea, and vomiting, especially during dose escalation. Growth hormone peptides (CJC-1295, Ipamorelin, MK-677) may cause water retention, increased hunger, and mild fatigue. BPC-157 has an excellent safety profile in animal studies with few reported human side effects. Melanotan II and PT-141 can cause facial flushing, nausea, and spontaneous erections. Always research compound-specific profiles before use.