Injection sites the trial protocols used

The documents this page reports from

Three record types, not forum consensus: the ClinicalTrials.gov registry entry, which states the route each arm received, the clinical pharmacology section of the approved label, which reports which site the sampling study dosed, and the dosage and administration section, which names the regions the program allowed.

What each one can settle: the registry entry settles route. SURPASS-2, registered as NCT03987919, records both tirzepatide and semaglutide as administered subcutaneously across a 1879-patient phase 3 trial.

What the registry cannot settle: the specific region. Registry intervention text is short, so every site list on this page is taken from a label section rather than from a protocol record.

What we cut: any site claim we could not tie to one of the three. Where a document is silent, this page says so rather than filling the gap.

The site lists, product by product

How to read the table: each row reproduces the regions one label names for its own product, plus the rotation language that sits beside it. No row is a recommendation and no row transfers to a different product.

The detail that is easy to drop: the tirzepatide labels split the arm out. The abdomen and thigh sit in the self-injection language, and the back of the upper arm appears only where another person gives the injection.

What the exposure work found across sites

The tirzepatide finding: the Mounjaro and Zepbound clinical pharmacology sections report that similar exposure was achieved with subcutaneous administration in the abdomen, thigh or upper arm. Mean absolute bioavailability is reported at 80%.

The semaglutide finding: the Ozempic and Wegovy sections report the same result in the same three regions, with absolute bioavailability at 89% by the subcutaneous route.

Which site the growth hormone studies used: the Genotropin section reports a 0.03 mg/kg subcutaneous injection in the thigh returning roughly 80% of the intravenous exposure in adults with growth hormone deficiency. Norditropin reports its own thigh-dosed study in 18 adult patients.

What the equivalence claim covers: those specific products at those specific sites. It is a finding about two large lipidated peptides, and neither label extends it to anything else.

The protocols that name one site and stop

Tesamorelin: the Egrifta SV label names the abdomen and nothing else, with rotation to different areas of the abdomen and an exclusion for scar tissue, bruises and the navel. One of the two pivotal trials behind it randomized 412 patients with HIV-associated lipodystrophy and excess abdominal fat to a daily subcutaneous injection of 2mg of tesamorelin or placebo for 26 weeks.

What that program measured: the primary endpoint was the percent change in visceral adipose tissue on computed tomography. Separately, and pooled across the clinical trials rather than from the 412-patient study alone, the label reports the injection site reaction rate at 25% against 14% on placebo over the first 26 weeks. Neither figure states why the abdomen was the site chosen, and the label does not say.

Octreotide as a depot: the Sandostatin LAR Depot label names the gluteal region at four-week intervals and states that deltoid injections should be avoided because of significant discomfort at that site. The label gives its own reason there, which most of the site lists on this page do not.

The pattern worth keeping: a narrow site list usually tracks the formulation and the endpoint, not the molecule. The route page works through the same split from the other direction.

Which injection sites do the trial protocols name?

Three regions dominate the subcutaneous programs: the abdomen, the thigh and the upper arm. The semaglutide labels name all three. The tirzepatide labels name abdomen and thigh for self-injection and reserve the back of the upper arm for an injection given by someone else.

Outside that group: the somatropin labels add the buttocks, Egrifta SV narrows to the abdomen alone, and the two intramuscular depots move to the gluteal region, with Lupron Depot also naming the anterior thigh and the deltoid.

What none of them do: rank the regions. Not one of these documents states that one allowed site works better than another allowed site.

Does the injection site change how much drug is absorbed?

For the two compounds with a published answer in the label, no. Both tirzepatide labels and both semaglutide labels report similar exposure across the abdomen, thigh and upper arm, which is why the Wegovy label states the site can change without a dosage modification.

The limit on that answer: it was generated for those molecules, in those regions, by the subcutaneous route. Nothing in either document extends it to a different peptide, a different formulation or a different route.

Where the labels are silent: the somatropin documents report exposure from thigh-dosed studies without publishing a site comparison, so their site lists rest on tolerability language rather than on an equivalence finding.

Why do the protocols specify rotating the site?

Tissue damage at a repeated site, and the labels name it directly. Norditropin states that somatropin given subcutaneously at the same site over a long period can cause tissue atrophy, and puts rotation in the same sentence as the reason.

The insulin version of the same warning: the Humalog label ties rotation within a region to reducing the risk of lipodystrophy and localized cutaneous amyloidosis, and states that injection into an affected area is not to be done.

The rat data behind the octreotide line: the Sandostatin label reports injection-site sarcomas or squamous cell carcinomas in a 116-week subcutaneous rat study at the highest dose, says the increase was most probably caused by irritation and by the high sensitivity of the rat to repeated subcutaneous injections at one site, and notes no such reports in patients treated up to five years.

What do the protocols record when the drug is not injected?

They record no site at all, because there is none. The enobosarm cancer cachexia trial gave a once-daily oral dose or placebo across a 159-patient safety population, 52 of whom received placebo, and the registry entry lists the intervention without a route to a body region.

Why that contrast is useful: injection-site language is a property of injected drugs, and most of the compounds people compare against peptides are not injected. The SARMs comparison covers why that split is chemical rather than arbitrary.

Inside one molecule: semaglutide runs both ways. Wegovy has an injection with three named regions and a tablet with none, and the label reports absolute bioavailability of about 1% to 2% for the oral form against 89% subcutaneous.

Which labels include the buttocks as an injection region?

Three of the documents on this page. Norditropin names the back of the upper arm, abdomen, buttock or thigh. Genotropin names the thigh, buttocks or abdomen. Humalog names the abdominal wall, thigh, upper arm or buttocks.

Which ones do not: the tirzepatide and semaglutide labels, which stop at abdomen, thigh and upper arm, and Egrifta SV, which stops at the abdomen.

Where the lists diverge: the documents do not cite a common source for their site lists, and none of them explains how its own list was arrived at. We report the divergence rather than an account of it.

Why do the tirzepatide labels treat the upper arm differently?

Because they split the region by who is holding the pen. The Mounjaro and Zepbound labels put the abdomen and thigh in the general administration line and place the back of the upper arm in the clause covering an injection given by another person.

What the semaglutide labels do instead: list the abdomen, thigh and upper arm together, without that split, in section 2.1.

Why the detail survives compression badly: flattening both labels to the same three regions loses the one structural difference between them, and the split is easy to miss because it sits in a subordinate clause.

More from the library

Where this sits: five adjacent pages, each reading a different class of document off the same shelf.

• Subcutaneous vs intramuscular: which route each label is titled for, and which route each one excludes.
• Needle gauges and syringe sizes: the hardware specifications that travel with those site lists.
• Tirzepatide vs semaglutide: what the one head-to-head trial between them actually measured.
• Storage after reconstitution: what the labels state about a vial once water is in it.
• Semaglutide dosage guide: the trial record for the compound with the widest site list above.

Once a week: one protocol read of this kind goes out in the weekly briefing, free.

Sources

What this page is built from: eleven prescribing information documents and three published trials with their registry entries, each cited for its own product or its own protocol.

Last reviewed: 27 July 2026.

1. 1

   Mounjaro (tirzepatide) injection, for subcutaneous use. Prescribing information, Eli Lilly and Company. Sections 2.2 and 12.3. DailyMed SPL, set id d2d7da5d-ad07-4228-955f-cf7e355c8cc0.

2. 2

   Zepbound (tirzepatide) injection, for subcutaneous use. Prescribing information, Eli Lilly and Company. Sections 2.4 and 12.3. DailyMed SPL, set id 487cd7e7-434c-4925-99fa-aa80b1cc776b.

3. 3

   Ozempic (semaglutide) injection, for subcutaneous use. Prescribing information, Novo Nordisk. Sections 2.1 and 12.3. DailyMed SPL, set id adec4fd2-6858-4c99-91d4-531f5f2a2d79.

4. 4

   Wegovy (semaglutide) injection, for subcutaneous use; Wegovy (semaglutide) tablets, for oral use. Prescribing information, Novo Nordisk. Sections 2.1 and 12.3. DailyMed SPL, set id ee06186f-2aa3-4990-a760-757579d8f77b.

5. 5

   Norditropin (somatropin) injection, for subcutaneous use. Prescribing information, Novo Nordisk. Sections 2.1, 5, and 12.3. DailyMed SPL, set id 1058e17c-9261-459c-a3e6-fae38d196c14.

6. 6

   Genotropin (somatropin) for injection, for subcutaneous use. Prescribing information, Pfizer. Sections 2.3, 5, 12.3, and Instructions for Use. DailyMed SPL, set id ffebf88b-d257-4542-9808-74d9b7167765.

7. 7

   Humalog (insulin lispro) injection, for subcutaneous or intravenous use. Prescribing information, Eli Lilly and Company. Sections 2.2 and 5.2. DailyMed SPL, set id c8ecbd7a-0e22-4fc7-a503-faa58c1b6f3f.

8. 8

   Egrifta SV (tesamorelin) for injection, for subcutaneous use. Prescribing information, Theratechnologies. Sections 2.1 and 5.6. DailyMed SPL, set id 3d783378-b02d-4f19-99dd-0fc91a042224.

9. 9

   Sandostatin LAR Depot (octreotide acetate) for injectable suspension, for gluteal intramuscular use. Prescribing information, Novartis. Section 2. DailyMed SPL, set id d0b7fe9e-7000-4b79-ba3b-291ce92c14f9.

10. 10

    Sandostatin (octreotide acetate) injection. Prescribing information, Novartis. Sections 2.1 and 13.1. DailyMed SPL, set id 4e2c9856-1836-49f0-9472-4dbeeb408f39.

11. 11

    Lupron Depot (leuprolide acetate) for depot suspension. Prescribing information, AbbVie. Section 2.5. DailyMed SPL, set id cbc8f94e-7330-4465-05ad-16d64493a5dd.

12. 12

    Frias JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. N Engl J Med. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519. PMID 34170647. Registered as NCT03987919.

13. 13

    Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359-2370. doi:10.1056/NEJMoa072375. PMID 18057338. Registered as NCT00123253.

14. 14

    Dobs AS, Boccia RV, Croot CC, et al. Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial. Lancet Oncol. 2013;14(4):335-345. doi:10.1016/S1470-2045(13)70055-X. PMID 23499390. Registered as NCT00467844.