Subcutaneous Injection

A subcutaneous injection delivers a substance into the layer of fat just beneath the skin — not into muscle (intramuscular) and not into a vein (intravenous). The subcutaneous tissue is well-vascularised but absorbs compounds more slowly than a direct venous injection, which makes it suitable for peptides that need a controlled release into the bloodstream. For most research peptides, subcutaneous is the standard administration route because it's the route used in the animal studies and clinical trials that generated the evidence base. It's also practically accessible: the abdomen, thigh, and upper arm are common sites, using small-gauge (usually 27–30G) needles. The fact that a peptide requires subcutaneous injection is one of the constraints on its practicality in a clinical context — daily injections are a compliance barrier that orally bioavailable drugs don't face. BPC-157 research into oral administration is partly driven by this practicality consideration, though the oral bioavailability question is unresolved. A subcutaneous injection is not a medical recommendation. The administration method and any protocols are decisions for a licensed practitioner.