Glossary
Intramuscular
An injection delivered directly into muscle tissue, abbreviated as IM, providing faster absorption than subcutaneous injection.
Also known as:
IM intramuscular injection
Intramuscular injections are administered into major muscle groups — most commonly the deltoid (shoulder), vastus lateralis (outer thigh), or gluteal muscles. The rich blood supply in muscle tissue means compounds are absorbed more quickly than via subcutaneous injection.
IM injections require longer needles (typically 21–25 gauge, 1–1.5 inch) and more precise technique to avoid nerves and blood vessels. While less common for peptides than SubQ, IM is sometimes preferred for compounds where rapid onset is important or where large injection volumes are needed.