What Are Peptides?
Short chains of amino acids that carry signals between cells.
Last reviewed September 1, 2026
A peptide is a short chain of amino acids joined by peptide bonds. Most definitions place the boundary at roughly 50 amino acids: shorter chains are peptides, longer ones are proteins.
Your body makes thousands of them. Insulin, oxytocin, glucagon and GLP-1 are all peptides. They generally work as signals, binding a receptor on a cell surface and changing that cell's behaviour.
Why they are studied as drugs
Peptides are often highly selective for their target, which can mean fewer off-target effects than small molecules. The trade-off is that digestive enzymes break them down, so most require injection rather than swallowing.
Much of modern peptide drug design is about defeating that fragility — modifying sequences and attaching fatty acid chains so a molecule survives long enough to act.