Intramuscular Injection
Also known as: IM
Intramuscular injection delivers a compound directly into muscle tissue. It is used for some research peptides and typically results in faster peak absorption than subcutaneous injection.
Overview
Intramuscular injections penetrate through skin and subcutaneous fat to deposit the compound directly within a muscle belly. Common sites include the deltoid, vastus lateralis (outer thigh), and gluteus medius. Muscle tissue is highly vascularized, so absorption can be faster than subcutaneous for some compounds. Intramuscular injections typically use longer, larger-gauge needles (21G–25G, 1–1.5 inches) than subcutaneous injections and are generally considered more uncomfortable. Most research peptides are administered subcutaneously rather than intramuscularly because subQ achieves comparable or equivalent bioavailability with a simpler, less painful technique.
Related Terms
Frequently asked questions
Which peptides are given intramuscularly versus subcutaneously?+
Most research peptides use the subcutaneous route. Intramuscular injection may be specified in some protocols where faster absorption kinetics are studied, but subQ is the default for most research peptides.
What needle gauge is used for intramuscular injections?+
Typically 21G–25G needles, 1–1.5 inches long, are used for IM injection to reach muscle depth through skin and subcutaneous tissue.
Does IM injection hurt more than subQ?+
Generally yes. Muscle tissue is denser and more sensitive than subcutaneous fat, and IM injections use larger needles. SubQ injections with short, fine needles are typically less uncomfortable.