Subcutaneous (SubQ) injection
The most common method for research peptides. Inject into the fatty tissue just beneath the skin — typically the abdomen, thigh, or upper arm. Use a short (4–6mm) insulin needle at a 45–90° angle. Rotate injection sites to avoid lipodystrophy (fat tissue changes). SubQ injections are slower to absorb than IM but are easier to self-administer.
Intramuscular (IM) injection
IM injections deliver the peptide directly into muscle tissue, resulting in faster absorption. Common sites include the deltoid, vastus lateralis (outer thigh), or gluteus medius. Use a longer needle (16–25mm) at 90°. IM is less common for peptides but may be preferred for TB-500 and some other compounds.
Nasal spray
Some peptides — particularly Selank, Semax, and PT-141 — are available as nasal sprays. This method bypasses first-pass metabolism and allows direct delivery to the bloodstream via the nasal mucosa. Bioavailability is lower than injection but the method is needle-free and convenient. Nasal sprays require careful storage and have a shorter shelf life once opened.
Oral administration
Most peptides are destroyed by digestive enzymes before reaching the bloodstream, making oral administration ineffective for the majority of compounds. BPC-157 is a notable exception — some evidence suggests oral BPC-157 retains activity in the gut, making it useful for gastrointestinal conditions. Always verify whether a specific peptide has demonstrated oral bioavailability before choosing this route.
Key takeaways
- SubQ injection is the most common and practical method for most peptides
- Rotate injection sites to prevent tissue damage
- Nasal sprays work for select peptides (Selank, PT-141) but have lower bioavailability
- Most peptides are not orally bioavailable — BPC-157 is a key exception