Intramuscular (IM) Injection
Also known as: IM · intramuscular injection
Injection directly into muscle tissue, typically using a longer needle than subcutaneous injection.
IM injection reaches muscle, which has denser vasculature than subcutaneous fat, producing faster absorption for most compounds. IM is standard for oil-based compounds and some water-based peptides where faster absorption is specifically desired. Typical IM sites include the deltoid, vastus lateralis (outer quad), and ventrogluteal.
IM injection requires a longer needle (typically 1–1.5 inch, 22–25 gauge) to reliably cross the subcutaneous layer into muscle. Most research peptides do not require IM — SubQ is the default and easier route. IM is mechanism-driven, not convenience-driven.
Related Terms
Subcutaneous (SubQ) Injection
Injection into the fatty layer immediately beneath the skin and above muscle tissue.
Injection Site Rotation
The practice of varying injection location across sessions to prevent tissue irritation, lipohypertrophy, and absorption inconsistency.
Insulin Syringe
A small-gauge, low-volume syringe (typically 29–31 gauge, 0.3–1mL capacity) calibrated in insulin units for subcutaneous injection.
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