Why the route matters
Many peptides are broken down by digestive enzymes, so the same amount taken by mouth and by injection can behave very differently. When a profile says “routes studied”, it lists the routes researchers actually tested — not the routes people use.
If the human research used eye drops and the community injects, that gap matters. TB-500 is a clear example.
The routes
Subcutaneous (SC)
Into the fat layer just under the skin, with a short insulin needle. The most common route in peptide research and community reports. Absorbed steadily over minutes to hours.
Intramuscular (IM)
Into a muscle. Often absorbed faster than . Used in some clinical studies and for some approved medicines.
Intravenous (IV)
Directly into a vein. Used in clinical trials under supervision. Not something done outside a clinic.
Oral
By mouth. Most peptides are digested before they reach the blood; a few are studied orally because they are unusually stable or specially formulated (oral semaglutide uses an absorption enhancer).
Nasal
Sprayed into the nose, where a thin lining allows some absorption. Studied for several neuro-active peptides. Dosing is less precise.
Topical
Applied to the skin. Used mainly for cosmetic and wound-healing research. Whether a peptide penetrates deeply enough to act is often the open question.
Reading the research
When you read a study, check three things: the route, the dose per kilogram, and the species. A rodent dose given into the abdomen (intraperitoneal) tells you little about a human dose given under the skin.