Why most peptides are injected
Peptides are fragile. Taken as a pill, most are chopped up by stomach acid and digestive enzymes before they ever reach the bloodstream, and even the survivors are often too large to cross the gut wall efficiently. This 'low oral bioavailability' is the central engineering problem of peptide medicine, and it's why injection — which bypasses the gut entirely — is the default route.
It's also why the rare oral peptide products are a genuine feat of formulation rather than the norm.
The common routes, explained
Subcutaneous injection — a small injection into the fat layer just under the skin — is the most common route for peptide therapy. Absorption from this layer is gradual and predictable, and it's a route many patients can be taught to do at home under provider direction.
Intramuscular injection delivers into muscle, which has a richer blood supply and can change how quickly a peptide is absorbed. Intravenous (IV) administration puts the peptide directly into the bloodstream and is done in a clinical setting. A few peptides are given as a nasal spray, absorbed across the nasal lining, and a small number are formulated for oral use. Each peptide's profile lists its route.
Route and dose are provider-directed
The route, the schedule, and the specifics are clinical decisions your provider makes for your prescription — they aren't things to improvise from a forum post. If a provider prescribes a peptide, your care team gives you exactly the guidance you need for that prescription.
We intentionally don't publish self-administration walkthroughs or dosing calculators. That's not a limitation of this site; it's part of treating peptides as the supervised medical service they are.