SARMs vs peptides: different molecules, different rules

What each class is made of

The peptide side: a sequence of amino acids, sometimes modified with a fatty acid or a cyclic bridge. Octreotide is a cyclic octapeptide at 1019.3 g/mol, tesamorelin is 44 residues at 5135.9 Da, and somatropin is 191 residues at about 22,124 daltons.

The SARM side: synthetic organic molecules with no amino acid backbone at all. The FDA warning letter that named ostarine identified it by an organic chemical name of the propanamide type, and identified LGD-4033 by a benzonitrile-type name.

What that difference costs each class: a peptide chain is a protease target, which is why the injected products dominate that side. A small molecule can survive a first pass and be swallowed.

Where the masses land on the peptide side: octreotide at 1019.3 g/mol, tesamorelin at 5135.9 Da and somatropin at about 22,124 daltons, each from its own label. We have not sourced a molecular weight for any SARM on this page, so no mass comparison between the classes is drawn here.

What each one binds, and why selectivity is the whole pitch

The receptor: the androgen receptor is a member of the steroid hormone receptor family, and its normal ligands are circulating testosterone and locally synthesized dihydrotestosterone. It sits inside the cell, so a ligand has to get in.

The problem SARMs were built for: the 2018 Narayanan review of SARM development names ubiquitous receptor expression, metabolism and cross-reactivity with other receptors as the limits on broad therapeutic use of steroidal androgens, with tissue-selective modulators proposed as the way past that.

What the peptide side does instead: the labeled peptide products act at receptors for specific hormones, so semaglutide is described as a GLP-1 receptor agonist and tirzepatide as a dual GIP and GLP-1 receptor agonist. Selectivity there comes from which receptor is targeted, not from tissue behavior at a shared one.

The practical read: the compounds in these two groups act at different receptors, and peptides as a chemical class act across several receptor families rather than one. Nothing about the two mechanisms makes their numbers interchangeable.

What the FDA has put in writing

The supplement exclusion: a 2017 warning letter states that products containing ostarine and LGD-4033 do not meet the dietary supplement definition in section 201(ff) of the FD&C Act, because neither compound was marketed as a supplement or a food before it was authorized for investigation as a new drug.

The drug finding: the same letter concludes the products are drugs under section 201(g)(1)(C), because their marketing claims showed an intent to affect the structure or function of the body, and new drugs under section 201(p) because they are not generally recognized as safe and effective.

The prescription finding on top of it: the letter goes further and calls them prescription drugs under section 503(b)(1)(A), citing toxicity, and names liver toxicity, adverse effects on blood lipid levels and a potential to increase the risk of heart attack and stroke.

The consumer-facing version: an FDA consumer update current as of 26 April 2023 states that SARMs are not FDA approved and cannot be legally marketed in the United States as a dietary supplement or a drug, listing liver injury and acute liver failure, heart attack or stroke risk, psychosis, infertility and testicular shrinkage among reported problems.

Two different prohibited classes, not one

Where SARMs sit: the 2026 Prohibited List puts selective androgen receptor modulators in S1.2, other anabolic agents, alongside clenbuterol, osilodrostat, ractopamine, zeranol and zilpaterol. The named examples are andarine, enobosarm, LGD-4033, RAD140, S-23 and YK-11.

Where the peptide hormones sit: section S2, peptide hormones, growth factors, related substances and mimetics, a different class entirely, covering growth hormone, its releasing factors and thymosin-beta 4 with its derivatives. S2 is not a class for every peptide, only for the ones the list enumerates.

What both share: prohibition at all times, in and out of competition, with every substance in each class listed as a non-specified substance.

Why the split is informative: the list files these compounds in two separate classes with two separate headings, whatever a storefront groups them under. The list does not state why it draws the line where it does, and we do not put words in it.

What was actually inside products sold as SARMs

The study: 44 products marketed and sold online as selective androgen receptor modulators were bought and analyzed with anti-doping laboratory procedures, and the results were published in JAMA in 2017.

What else was found: the paper names ibutamoren, GW501516 and SR9009 among the other unapproved drugs detected, none of which is a SARM. Substances not listed on the label appeared in 25% of the products.

The reason this belongs in a class comparison: a label on a product bought this way is not evidence of what is in it. Any comparison between two compounds assumes both bottles contain what they claim, and in this sample of 44 products that assumption held for 18.

Are SARMs peptides?

No. SARMs are nonsteroidal small molecules with no amino acid chain, and the 2018 Narayanan review describes them as ligands for the androgen receptor. Peptides are amino acid chains, which is what the word means.

Why the two get filed together anyway: the same shops sell them, the same forums discuss them, and both are frequently labeled for research use. Shared distribution is not shared chemistry.

The clearest tell: the FDA warning letter identifies ostarine by an organic chemical name. The peptide labels cited here print an amino acid count, and in several cases a sequence, instead.

Can SARMs be sold as dietary supplements?

Not according to the agency. The FDA consumer update states that SARMs cannot be legally marketed in the United States as a dietary supplement or a drug, and warning letters have applied the statutory exclusion directly: an article authorized for investigation as a new drug, with substantial public clinical investigations, is outside the supplement definition unless it was on the market as a food or supplement first.

What the agency did about it: the same update says warning letters have gone out to companies selling unapproved products marketed as SARMs over the years, and that criminal actions have been pursued against distributors.

What none of that establishes: anything about a specific product in front of a specific reader. This is the regulatory record, not a verdict on a bottle.

Why are SARMs taken orally when most peptides are injected?

Molecule size and digestion. The clinical work on enobosarm used a once-daily oral capsule in a 159-patient phase 2 trial, which is a normal route for a small molecule. Amino acid chains face proteases in the gut, which is why the approved peptide products carry an injection route.

The exception that proves the rule: oral semaglutide exists, and the Wegovy label, which covers both the injection and the tablet, reports absolute bioavailability of about 1% to 2% after the oral tablet against 89% after subcutaneous administration. Getting a peptide through the gut costs most of the dose.

What the route difference drags with it: everything on the administration side. Our route page covers what the injected labels specify, and none of it applies to an oral compound.

What did laboratory testing find inside products sold as SARMs?

Mostly something other than the label. In the 2017 JAMA analysis of 44 internet-sold products, 23 contained one or more SARMs of any kind, which the paper lists as ostarine, LGD-4033 or andarine and which need not be the one on the label, 17 contained a different unapproved drug, and 4 contained no active compound at all.

The dosing accuracy question: the printed amount matched the analyzed amount in 18 of 44 products, so the quantity differed substantially in the other 26.

Why we keep returning to this figure: a comparison between two compounds assumes the compounds are what they say. Our page on why charts disagree works through what that uncertainty does to arithmetic downstream.

Do SARMs and peptides fall under the same anti-doping class?

No. The 2026 Prohibited List puts selective androgen receptor modulators in S1.2, other anabolic agents, and peptide hormones in S2. Two sections, two headings, two different sets of named examples.

What they have in common: both classes are prohibited at all times, in and out of competition, and every substance in each is a non-specified substance.

What the separation encodes: the list groups by biological effect, so a split at that level is a statement that the two are not doing the same job in the body.

What risks has the FDA named for SARMs in writing?

The consumer update lists increased risk of heart attack or stroke, psychosis and hallucinations, sleep disturbances, sexual dysfunction, liver injury and acute liver failure, infertility, pregnancy miscarriage and testicular shrinkage.

The warning letter version: the 2017 letter names life-threatening reactions including liver toxicity, and says the long-term safety profile remains unclear with more clinical evidence needed on liver toxicity, blood lipid effects and cardiovascular risk.

The reporting caveat the agency adds itself: the update says the real number of consumers experiencing adverse events is likely higher than the reports received, because these are not approved drugs.

More from the library

Nearby: five pages covering the classification, the arithmetic and the individual compounds named above.

• HGH vs peptides: the other class comparison, where the split runs by chain length instead of receptor family.
• Tirzepatide vs semaglutide: what a comparison looks like when one trial ran both arms itself.
• Why dosing charts disagree: what unverified contents do to every number downstream.
• BPC-157 guide: the research record for a short peptide with no approval behind it.
• Injection sites in the trials: the protocol detail that only exists on the injected side of this comparison.

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

Sources

What this page is built from: two FDA documents, one anti-doping standard, three published papers and four prescribing information documents, ten in all. Every figure above traces to one of them.

Last reviewed: 27 July 2026.

1. 1

   Egrifta SV (tesamorelin) for injection, for subcutaneous use. Prescribing information, Theratechnologies. Section 11. DailyMed SPL, set id 3d783378-b02d-4f19-99dd-0fc91a042224.

2. 2

   Genotropin (somatropin) for injection, for subcutaneous use. Prescribing information, Pfizer. Section 11. DailyMed SPL, set id ffebf88b-d257-4542-9808-74d9b7167765.

3. 3

   Sandostatin (octreotide acetate) injection. Prescribing information, Novartis. Section 11. DailyMed SPL, set id 4e2c9856-1836-49f0-9472-4dbeeb408f39.

4. 4

   Wegovy (semaglutide) injection and tablets. Prescribing information, Novo Nordisk. Sections 11 and 12.3. DailyMed SPL, set id ee06186f-2aa3-4990-a760-757579d8f77b.

5. 5

   US Food and Drug Administration. Warning letter to Infantry Labs LLC, MARCS-CMS 535333, 23 October 2017. fda.gov warning letter 535333.

6. 6

   US Food and Drug Administration. FDA Warns of Use of Selective Androgen Receptor Modulators (SARMs) Among Teens, Young Adults. Consumer Update, content current as of 26 April 2023. fda.gov consumer update.

7. 7

   World Anti-Doping Agency. World Anti-Doping Code International Standard Prohibited List 2026, in effect 1 January 2026. Classes S1.2 and S2. wada-ama.org/en/prohibited-list.

8. 8

   Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D. Chemical Composition and Labeling of Substances Marketed as Selective Androgen Receptor Modulators and Sold via the Internet. JAMA. 2017;318(20):2004-2010. doi:10.1001/jama.2017.17069. PMID 29183075.

9. 9

   Narayanan R, Coss CC, Dalton JT. Development of selective androgen receptor modulators (SARMs). Mol Cell Endocrinol. 2018;465:134-142. doi:10.1016/j.mce.2017.06.013. PMID 28624515.

10. 10

    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.