What is Half-Life? (Peptide Glossary)

Half-life is the time required for half of a substance to be eliminated or degraded. It is the single most important pharmacokinetic property for research design because it dictates dosing frequency: a peptide with a 30-minute half-life (like Mod GRF 1-29) produces short pulsatile exposure, while a week-long half-life (like semaglutide) supports once-weekly administration.

Research peptide engineering is largely the art of extending half-life. Native peptides are often degraded within minutes by enzymes. Common stabilization strategies visible across compound profiles include fatty acid chains that bind albumin (semaglutide's C18 chain extends it to ~7 days), DAC (Drug Affinity Complex) conjugation in CJC-1295, D-amino acid substitutions that resist proteases, and cyclization (Melanotan II).

When comparing related compounds, half-life differences define their research use. CJC-1295 with DAC (6-8 day half-life) produces sustained GH elevation in research models, while the no-DAC version (30 minutes) produces physiological pulses - the same base molecule with opposite pharmacokinetic characters. Compound pages on this site list published half-life data for exactly this reason.