What is Subcutaneous? (Peptide Glossary)

Subcutaneous (SubQ) administration deposits a compound into the fat layer between skin and muscle, typically using a short, fine insulin needle. It is the dominant route in peptide research because it is simple, minimally invasive, and provides steady absorption - most published peptide research, from semaglutide trials to tesamorelin studies, used subcutaneous administration.

The absorption profile of subcutaneous injection sits between intravenous (immediate, complete) and oral (slow, poor for peptides). A subcutaneous depot releases the peptide into circulation over hours, which smooths the pharmacokinetic curve. For peptides engineered for long half-life, SubQ once daily or weekly is sufficient; for short-half-life secretagogues, multiple daily administrations appear in research protocols.

In laboratory practice, subcutaneous technique involves rotating sites (abdomen, thigh, upper arm in animal models), proper reconstitution hygiene, and bacteriostatic water for multi-use vials. Research-use-only compounds are not sterile-manufactured to pharmaceutical standards, which is one more reason they must never be used outside laboratory research.