The simplest definition
A peptide is a short chain of amino acids — usually between 2 and 50 — linked by peptide bonds. Think of them as tiny messengers. They do not build tissue directly like protein; instead, theysignal your cells to behave in specific ways. Some tell your pituitary to release growth hormone. Others tell fibroblasts to lay down collagen. Some calm inflammation; others turn it up.
How peptides work in the body
Your body already makes thousands of peptides naturally. Insulin is a peptide. Oxytocin is a peptide. The ones used in research are either identical to human sequences or slightly modified to last longer or bind more strongly. When you inject a peptide subcutaneously, it enters the bloodstream, finds its receptor on a target cell, and triggers a cascade — usually within minutes to hours.
Because peptides are highly specific, they tend to have fewer off-target effects than small-molecule drugs. That specificity is why researchers study them for everything from tendon repair to fat loss to neuroprotection.
The most common categories
GLP-1 agonists like Tirzepatide and Retatrutide suppress appetite and improve glycemic control.
BPC-157 and TB-500 accelerate tendon, ligament, and gut-lining repair through angiogenesis.
CJC-1295, Ipamorelin, and Tesamorelin stimulate natural GH pulses without shutting down your axis.
Epitalon and FOXO4-DRI target cellular senescence and telomere maintenance.
Are peptides safe?
Peptides sold for research are not FDA-approved for human consumption. That said, many have extensive safety data from clinical trials — especially the bioregulators and GH secretagogues. The risks are generally dose-dependent and reversible: water retention, mild blood-sugar shifts, injection-site irritation, and rare allergic reactions. The best practice is to start low, use sterile technique, and source from a verified vendor.
How to get started
- 1Pick a goal. Fat loss, healing, muscle, sleep, or longevity. Use our peptide library to browse by category.
- 2Learn the protocol. Every peptide has a recommended dose, frequency, and cycle length. Read the full entry before ordering.
- 3Practice reconstitution. Our step-by-step guide walks you through mixing, drawing, and storing.
- 4Use the calculator. Enter your vial size and BAC water into our visual syringe tool so you never guess the draw.
Key terms to know
- Subcutaneous (SubQ)
- Injection into the fatty tissue under the skin — the standard method for most peptides.
- Reconstitution
- Mixing lyophilized (powder) peptide with bacteriostatic water to create an injectable solution.
- Mcg vs mg
- Micrograms (mcg) and milligrams (mg). 1 mg = 1,000 mcg. Most peptide doses are measured in mcg.
- Cycle
- A planned period of use followed by time off — e.g., 8 weeks on, 8 weeks off.