How are peptides typically administered?

Most therapeutic peptides are administered via subcutaneous injection because digestive enzymes destroy peptides taken orally. Subcutaneous injections go into the fatty tissue just beneath the skin, typically in the abdomen, thigh, or upper arm. This route provides steady absorption and bypasses first-pass metabolism. Some peptides have alternative administration routes: oral semaglutide (Rybelsus) uses absorption enhancers to survive digestion; PT-141 (Bremelanotide) is FDA-approved as a subcutaneous injection; GHK-Cu is commonly applied topically in skincare; and some peptides are formulated as nasal sprays (Semax, Selank). Subcutaneous peptide injections use small insulin syringes (29-31 gauge needles) that cause minimal discomfort. Patients typically learn to self-inject after demonstration by healthcare providers. Injection sites should be rotated to prevent lipohypertrophy (fatty tissue buildup). Peptides requiring frequent dosing often use compounded combinations to reduce injection burden. For those uncomfortable with injections, some providers offer clinical administration, though this is less practical for ongoing therapy.