Administration reference

Subcutaneous vs intramuscular: what the labels specify

By the Decadewise team Education only Last reviewed 27 July 2026 Label reporting only

Short answer

The definition: a subcutaneous injection deposits liquid in the fat layer under the skin, and an intramuscular injection deposits it inside the muscle below that layer. An approved label states the route or routes its own product was approved for, and several of the labels below also write an excluded route into the text.

What the metabolic labels specify: Mounjaro, Zepbound, Ozempic and Wegovy are each titled for subcutaneous use, and each instructions-for-use section carries a line against injecting into a muscle or a vein.

What the depot labels specify: Sandostatin LAR Depot is titled for gluteal intramuscular use and states it should never be given intravenously or subcutaneously. Lupron Depot is a single intramuscular injection.

Why the split exists: one molecule can hold both labels. Octreotide is subcutaneous as a solution and intramuscular as a microsphere suspension.

The scope: this page reports what named labels specify for their own products. It carries no procedure and no dose.

On this page

Short answer The two routes Each label rules one out Route follows the formulation What the absorption data shows SC vs IM? Why subcutaneous? Any intramuscular peptides? Can the routes be swapped? Does route change duration? Why two routes for one peptide? More from the library Sources The disclaimer

The two routes, as the labels title them

Route sits in the title line: an approved label states its route in the first line of the highlights, before any dosing text. Mounjaro reads as an injection for subcutaneous use, and Sandostatin LAR Depot reads as a suspension for gluteal intramuscular use. That line is not a suggestion inside the document, it is the document's own scope.

Subcutaneous, per the labels that use it

The tissue: the fat layer beneath the skin, which the labels reach through short needles and small volumes.

Products titled this way: tirzepatide as Mounjaro and Zepbound, semaglutide as Ozempic and Wegovy, somatropin as Norditropin and Genotropin, tesamorelin as Egrifta SV, octreotide as Sandostatin injection.

The volumes named: Mounjaro single-dose presentations hold 0.5mL, and the multi-dose presentations deliver 0.6mL per dose.

Intramuscular, per the labels that use it

The tissue: the muscle body itself, which the labels reach through longer and wider needles.

Products administered this way: octreotide as Sandostatin LAR Depot, which is titled for gluteal intramuscular use, and leuprolide as Lupron Depot, whose highlights title names no route and whose dosing section gives the injection intramuscularly. Both are long-acting suspensions rather than solutions.

The sites named: Sandostatin LAR Depot names the gluteal region. Lupron Depot names the gluteal area, the anterior thigh, or the deltoid.

What the pairing is not: the labels do not present the two routes as interchangeable options with different comfort levels. Where a document does write an exclusion, it sits in the same section as the instruction. Not every label writes one: Sandostatin injection is titled for subcutaneous or intravenous use and rules out neither of the others in that line.

Each label rules the other route out in writing

The subcutaneous side: the Mounjaro, Zepbound and Ozempic instructions for use each state that the product is not to go into a muscle or a vein. Wegovy carries the same line. Genotropin states that it must not be injected intravenously.

The intramuscular side: Sandostatin LAR Depot states that it should never be administered intravenously or subcutaneously. The prohibition runs in the opposite direction from the one on the metabolic labels, and it is just as explicit.

Why the exclusion line is worth reading: the permitted route tells you what the document reports data for. The excluded route tells you what the document instructs against, in its own words. Why each exclusion was written is not stated in the labels, so we do not infer it here.

The route line and the exclusion line, product by product

Product	Route in the label title	Route the label rules out
Mounjaro (tirzepatide)	subcutaneous use	intramuscular, intravenous
Zepbound (tirzepatide)	subcutaneous use	intramuscular, intravenous
Ozempic (semaglutide)	subcutaneous use	intramuscular, intravenous
Wegovy (semaglutide)	subcutaneous use	intramuscular, intravenous
Genotropin (somatropin)	subcutaneous use	intravenous
Sandostatin LAR Depot (octreotide)	gluteal intramuscular use	intravenous, subcutaneous

Every cell above is a statement each label makes about its own product.

Route follows the formulation, not the molecule

One molecule, two labels: octreotide is an eight amino acid cyclic peptide with a molecular weight of 1019.3 g/mol. Sandostatin injection is a clear solution of it, and its label covers subcutaneous or intravenous use. Sandostatin LAR Depot is the same peptide loaded into biodegradable microspheres, and its label covers gluteal intramuscular use only.

What changed between them: not the peptide, the carrier. The depot label describes release governed by the slow breakdown of the polymer microspheres in the muscle, which is the mechanism the four-week interval is built on.

The same pattern in leuprolide: Lupron Depot is lyophilized microspheres reconstituted from a dual-chamber syringe and given as a single intramuscular injection, at intervals its label sets at 4, 12, 16 or 24 weeks depending on the strength.

The reading that follows: asking whether a peptide is a subcutaneous drug or an intramuscular drug is the wrong question. The label answers for a specific formulation of it, and a different formulation of the same sequence can answer the opposite way.

What the absorption sections report about route

The subcutaneous depot effect: the Genotropin label reports a mean terminal half-life of 0.4 hours after intravenous dosing in normal adults against 3.0 hours after subcutaneous dosing in growth hormone deficient adults, and attributes the difference to slow absorption from the injection site. The two figures come from different populations, which is how the label prints them.

The same effect in a second somatropin: the Norditropin label reports a terminal half-life of about 21.1 minutes after an intravenous infusion and roughly 7 to 10 hours after a subcutaneous dose, again attributed to slow absorption from the site.

How much arrives: tirzepatide is reported at 80% mean absolute bioavailability by the subcutaneous route, semaglutide at 89%, and Genotropin at roughly 80% of the intravenous exposure. Octreotide is the outlier: its label reports subcutaneous and intravenous doses as bioequivalent.

Where a route can cost almost everything: the Egrifta SV label carries two tesamorelin figures from two different formulations, and prints them that way. Absolute bioavailability after subcutaneous dosing is reported at less than 4% for a 2mg dose of the original Egrifta, the 1mg per vial formulation, in healthy adults. The mean elimination half-life of 8 minutes is from a single 1.4mg dose of Egrifta SV, the 2mg per vial formulation, in healthy subjects. Two peptides can share a route and land nowhere near each other on either number.

What is the difference between a subcutaneous and an intramuscular injection?

The tissue the liquid ends up in, and everything the label builds on top of that. Subcutaneous means the fat layer under the skin, intramuscular means the muscle underneath it, and approved products are titled for one or the other in the first line of the prescribing information.

What the difference produces: the depot behavior is not the same. Both somatropin labels report a subcutaneous half-life several times the intravenous one and name slow absorption from the site as the reason.

What it does not decide: the milligram figure. Every dosing number on a label belongs to that label's own route, and it does not travel to a different one.

Why do the metabolic labels specify subcutaneous injection?

Because that is the route the injectable approvals were built on. The tirzepatide and semaglutide labels report their injectable exposure figures and their once-weekly interval from subcutaneous dosing, and both molecules are large: tirzepatide at 4813.53 Da, semaglutide at 4113.58 Da. Subcutaneous is not the only route semaglutide holds: the current Wegovy label covers a once-daily oral tablet alongside the injection, with its own dosing section and its own pharmacokinetics.

The protraction design: the semaglutide labels describe albumin binding as the main mechanism holding the molecule in circulation, with a maximum concentration reached 1 to 3 days after a dose. Tirzepatide reaches its peak at a median of 24 hours, in a range of 8 to 72 hours.

What the labels do not offer: a comparison arm at a different route. There is no intramuscular exposure figure in either document, which is why the exclusion line reads the way it does.

Are any peptide products labeled for intramuscular injection?

Yes, and the clearest cases are long-acting suspensions rather than solutions. Sandostatin LAR Depot, an octreotide microsphere suspension, is titled for gluteal intramuscular use. Lupron Depot, a leuprolide microsphere suspension, is given as a single intramuscular injection.

The site language differs too: the Sandostatin LAR Depot label names the gluteal region, states that sites are rotated systematically, and says deltoid injections should be avoided because of significant discomfort at that site.

The hardware differs with it: that label specifies a 1.5 inch 19 gauge safety needle supplied in the kit, with a 2 inch 19 gauge option named for patients with greater skin to muscle depth. The needle gauge page lays those specifications out beside the pen needles.

Can a subcutaneous product be given intramuscularly?

Not according to the documents. The tirzepatide and semaglutide instructions for use state plainly that the product is not to be injected into a muscle or a vein, and Sandostatin LAR Depot states the mirror image, that it should never go subcutaneously or intravenously. Those are exclusions printed in the labels themselves, not gaps a reader has to infer.

What sits beside the exclusion: none of these labels prints an exposure figure for the route it excludes. A number generated in the fat layer describes the fat layer.

What this page is not: a decision about anybody's own injection. That conversation belongs with a clinician who can see the person and the prescription.

Does the route change how long a peptide stays in circulation?

For the somatropin products it plainly does, and both labels say why. Genotropin reports a mean terminal half-life of 0.4 hours intravenously in normal adults against 3.0 hours subcutaneously in growth hormone deficient adults, and Norditropin reports about 21.1 minutes intravenously against 7 to 10 hours subcutaneously in growth hormone deficient patients, each attributing the gap to slow absorption out of the injection site.

The counterexample in the same set: the Sandostatin label reports octreotide absorbed rapidly and completely after a subcutaneous dose, with intravenous and subcutaneous doses found to be bioequivalent. Route is not always a duration lever.

What none of this licenses: reading one product's half-life onto another. These are three separate documents describing two separate molecules.

Why does one peptide end up with two different routes?

Because the approvals cover formulations rather than sequences. Octreotide holds a subcutaneous and intravenous label as a clear solution and a gluteal intramuscular label as a microsphere suspension. The exclusion runs one way in writing: the depot label states it should never be given intravenously or subcutaneously, while the solution label names its own two routes without ruling the depot's out.

What the depot format buys: the LAR label describes release governed by slow biodegradation of the polymer in the muscle, which is what turns a peptide dosed several times a day into one given every four weeks.

The reading to keep: the phrase "octreotide is a subcutaneous drug" is not true or false, it is underspecified. The label of the specific product answers it.

Sources

What this page is built from: ten current prescribing information documents, each cited for statements about its own product. Every route line, exclusion line and pharmacokinetic figure above traces to one of them.

Last reviewed: 27 July 2026.

1
Mounjaro (tirzepatide) injection, for subcutaneous use. Prescribing information, Eli Lilly and Company. Sections 2.2, 11, 12.3, and Instructions for Use. DailyMed SPL, set id d2d7da5d-ad07-4228-955f-cf7e355c8cc0.
2
Zepbound (tirzepatide) injection, for subcutaneous use. Prescribing information, Eli Lilly and Company. Sections 2.2, 11, 12.3, and Instructions for Use. DailyMed SPL, set id 487cd7e7-434c-4925-99fa-aa80b1cc776b.
3
Ozempic (semaglutide) injection, for subcutaneous use. Prescribing information, Novo Nordisk. Sections 2.1, 11, 12.3, and Instructions for Use. DailyMed SPL, set id adec4fd2-6858-4c99-91d4-531f5f2a2d79.
4
Wegovy (semaglutide) injection, for subcutaneous use. Prescribing information, Novo Nordisk. Sections 2.1, 11, 12.3, and Instructions for Use. DailyMed SPL, set id ee06186f-2aa3-4990-a760-757579d8f77b.
5
Genotropin (somatropin) for injection, for subcutaneous use. Prescribing information, Pfizer. Sections 2, 2.3, and 12.3. DailyMed SPL, set id ffebf88b-d257-4542-9808-74d9b7167765.
6
Norditropin (somatropin) injection, for subcutaneous use. Prescribing information, Novo Nordisk. Sections 2.1, 11, and 12.3. DailyMed SPL, set id 1058e17c-9261-459c-a3e6-fae38d196c14.
7
Sandostatin LAR Depot (octreotide acetate) for injectable suspension, for gluteal intramuscular use. Prescribing information, Novartis. Sections 2, 11, and 12.3. DailyMed SPL, set id d0b7fe9e-7000-4b79-ba3b-291ce92c14f9.
8
Sandostatin (octreotide acetate) injection, for subcutaneous or intravenous use. Prescribing information, Novartis. Sections 2.1, 11, and 12.3. DailyMed SPL, set id 4e2c9856-1836-49f0-9472-4dbeeb408f39.
9
Lupron Depot (leuprolide acetate for depot suspension). Prescribing information, AbbVie. Sections 2, 2.1 to 2.5, and 11. DailyMed SPL, set id cbc8f94e-7330-4465-05ad-16d64493a5dd.
10
Egrifta SV (tesamorelin) for injection, for subcutaneous use. Prescribing information, Theratechnologies. Sections 2.1, 11, and 12.3. DailyMed SPL, set id 3d783378-b02d-4f19-99dd-0fc91a042224.

The disclaimer

Every page is reviewed by medical professionals before it ships, and written with longtime biohackers who were doing this before it was a trend. Reviewed still does not mean prescribed: nothing here is medical advice.

It is research, trial data, and reported use, with the numbers intact so you can check them. For decisions about your body, see a doctor who can look at your labs.