What is the difference between peptide pills, nasal sprays and injections?

What the labels measure

Why a swallowed peptide mostly does not arrive

A peptide in the gut meets acid and protein-cutting enzymes, and even an intact one is large, polar and charged, which are poor traits for crossing the gut wall. A 2026 review in this area lists those properties together as the reason oral peptide bioavailability is low and often insufficient. Every swallowed product in the table above sits at or below 2%.

Low is not zero, and "digested" is not the whole story. The Rybelsus and Ozempic tablets label states that semaglutide absorption "predominantly occurs in the stomach", helped by the absorption enhancer SNAC, which a 2018 study found protects the peptide locally and only transiently raises absorption. Linaclotide (Linzess) is the opposite case: a swallowed peptide that its label calls minimally absorbed, with negligible systemic availability, because it acts on a receptor on the inner surface of the intestine and never needs to reach the blood.

Why nasal sprays land in between

The nose skips the stomach's enzymes and the liver's first pass, and the labels for nasal peptides report figures several times higher than the tablets: 2.8% for nafarelin and 3.3–4.1% for Stimate. Those are still small fractions. The Synarel label adds a practical limit of the route: sneezing during or just after a dose may impair absorption, and a decongestant is kept back for at least 2 hours after dosing.

Injections are higher, but not uniformly complete

Subcutaneous injection delivers 89% of a semaglutide dose and about 100% of a bremelanotide dose by their labels, and less than 4% of a tesamorelin dose by the Egrifta label. A 2014 review describes subcutaneous absorption of biotherapeutics as relatively slow and mostly incomplete. Intramuscular injection is not reliably better: one crossover study of hCG measured higher exposure after an intramuscular dose, a second found the two routes bioequivalent, and a study of recombinant FSH found no significant difference.

How the approved pills compensate

The Wegovy tablet label sets a 25 mg once-daily maintenance dose, 175 mg a week, against a 2.4 mg once-weekly maintenance injection: about 73 times the milligrams, by Prof. Peptide's arithmetic from the two label doses. The tablets also carry conditions the injection does not. The label directs an empty stomach, no more than 4 ounces of water, and at least 30 minutes before food, drink or other oral medicines.

For the adverse events reported at these label doses, see semaglutide side effects.

What the research market sells in these forms

Prof. Peptide read the public catalogs of 71 of its 83 listed vendors on October 7, 2026, and counted capsule or tablet products at 30 of them and spray, mist or atomizer products at 21. Only 3 of those vendors used the word "nasal" in a product title, so a "spray" listing is not necessarily a nasal one. These are Prof. Peptide's own counts of what is listed, not evidence that any of these products is absorbed, and none of them is an approved drug.

The record, compound by compound

For every peptide on this site that is sold or studied as a pill, see which peptides come in pill form.

For the nasal equivalent, see which peptides come as a nasal spray.