Subcutaneous Injection
Also known as: subQ, subcutaneous injection
Subcutaneous injection delivers a peptide into the fatty tissue just beneath the skin. It is the most common research administration route, abbreviated subQ, with approximately 80–100% bioavailability for most peptides.
Overview
The subcutaneous layer is a layer of fat and connective tissue that sits between the dermis and muscle. It contains abundant capillaries, allowing peptides to absorb into systemic circulation efficiently. Subcutaneous injections are made at a 45–90 degree angle with a short, thin needle (27G–31G) into pinched skin at sites such as the abdomen, outer thigh, or the back of the upper arm. Absorption from subcutaneous tissue is generally slower than intramuscular injection but more consistent. Rotating injection sites prevents lipodystrophy (fat tissue changes at the injection site). The high bioavailability and relative simplicity of the technique make subQ the standard method for most research peptide protocols.
Related Terms
Frequently asked questions
How deep is a subcutaneous injection?+
Subcutaneous injections target the fat layer just beneath the skin, typically 4–8 mm deep. A short insulin needle (4–8 mm) at a 45–90° angle is appropriate.
What are the best sites for subcutaneous injection?+
The abdomen (2 inches from the navel), outer thighs, and back of the upper arm are the most common sites. The abdomen has the most subcutaneous fat and is often the easiest site.
Should I rotate injection sites?+
Yes. Repeated injections at the same site can cause lipodystrophy (changes in fat tissue) and affect absorption. Rotating sites maintains consistent bioavailability and reduces tissue damage.