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SafetyEvidence-BasedSep 2026

MOTS-c Side Effects: What the Studies Report

MOTS-c side effects sit on unusually thin evidence. No completed clinical trial has ever given MOTS-c itself to a person and reported what happened, so the honest starting point is that the peptide has no established human safety profile at all.5 What exists instead is a scatter of adjacent findings: one completed Phase 1 trial of CB4211, a compound its maker CohBar called an analog of MOTS-c, where the main reported reaction was at the injection site;2 animal studies that mostly report benefit but include a few adverse signals; and a set of anecdotal reports from people who buy the peptide online, which anti-doping regulators repeat but label as anecdotal, not trial data.5 MOTS-c is also banned in sport at all times and is not approved by the FDA for human use.5 This page sorts what the studies actually report from what they do not, and it does not tell anyone what to take.

This is general education, not medical advice, and not a diagnosis. It describes what clinical registries, company disclosures, animal studies, regulators and vendor pages actually report about MOTS-c safety, and it labels the evidence level for every figure. MOTS-c is banned in sport and is not approved by the FDA for human use. Nothing below is a dose to take, a schedule, or an instruction to use MOTS-c or its analogs. The two dose figures on this page appear only to show what a company trial and an animal study recorded, each marked as not a recommendation.

The honest answer: no human safety profile

The reason MOTS-c side effects are hard to pin down is that the peptide has never been through the study that would define them. Every human study of MOTS-c itself that this page could fetch measured it as a biomarker, a molecule the body makes, rather than giving it as a drug. In one observational cohort of type 2 diabetics with coronary artery disease, low natural MOTS-c was itself a marker of risk: a serum level below 167 ng/ml predicted major adverse cardiovascular events, and low MOTS-c alongside high on-treatment platelet reactivity marked a roughly fourfold higher risk over two years (observational cohort, MOTS-c measured not administered, PMID 32052315).10 Other human work simply tracked endogenous MOTS-c rising with exercise.21 None of it dosed anyone, so none of it reports side effects.

That leaves three imperfect windows on safety, and this page works through each: one completed trial of the analog CB4211, the animal literature, and a body of anecdotal user reports that regulators repeat but do not endorse. For what MOTS-c is and how it is studied, the MOTS-c profile covers the molecule; this page is the MOTS-c-specific companion to the broader peptide side effects guide. No human trial has tested MOTS-c at any dose or schedule, microdosing included, so any protocol circulating online is untested by definition.

The human data: one trial, of an analog

No completed clinical trial has ever administered MOTS-c to people and reported adverse events, so the nearest thing to human safety data comes from a different molecule. CB4211 reached human testing, and its maker CohBar described it as "a novel and improved analog of MOTS-c".2 That description comes from the company: the trial registry never labels CB4211 a MOTS-c analog and cites only a mouse study as its MOTS-c reference,111 and among the sources fetched for this page, the only other source that calls it an analog is a research-foundation review, not an independent study of the compound.4 So read what follows as adjacent evidence, not as MOTS-c safety data.

The trial itself, registry identifier NCT03998514, was a Phase 1a/1b randomized, double-blind, placebo-controlled study in 88 participants, listed as completed, whose primary outcomes were the incidence and severity of adverse events and treatment-related injection site reactions. The registry posted no results table.1 The Phase 1a stage tested single and multiple ascending subcutaneous doses in 65 healthy adults; the Phase 1b stage dosed obese subjects with nonalcoholic fatty liver disease, 20 in the company results release and 23 randomized in the investor deck.23 In that Phase 1b portion, subjects received a 25 mg dose of CB4211 once daily by subcutaneous injection for four weeks (trial dose, not a recommendation, CohBar Phase 1b company release).2

What CohBar reported, in a press release and an investor presentation rather than a peer-reviewed paper, was that CB4211 was "well-tolerated and appeared safe with no serious adverse events".23 The most common adverse events were "transient and generally mild to moderate injection site reactions",2 and the investor presentation put their incidence at 79% of people on CB4211 against 33% on placebo.3 Injection-site trouble had shadowed the program before: a research-foundation review, citing CohBar, notes the study was temporarily paused in 2018 to address persistent mild injection site reactions described as "persistent painless bumps", thought to reflect some CB4211 remaining at the injection site.4 Full safety data have not been disclosed, so even this analog leaves no complete human safety record.4

What the animal studies report

Almost all of the MOTS-c evidence is preclinical, and most of it is not about harm at all. Across the fetched animal literature MOTS-c mostly shows protective or therapeutic effects, and several of those papers reach for explicit tolerability language: a 2024 ovarian cancer study, for instance, reported that MOTS-c produced its anti-tumor effect "without systemic toxicity in vivo".15 That is the general texture of the animal work, benefit reported, harm rarely the thing being looked for.

The mouse study the CB4211 trial registry actually cites is a neuropathic-pain experiment, where intrathecal MOTS-c produced dose-dependent pain relief and, as the authors put it, "limited side effects relating to antinociceptive tolerance, gastrointestinal transit inhibition, locomotor function, and motor coordination".11 Even the safety-adjacent language here is about how little went wrong in a short animal experiment, not a systematic safety study.

Two findings cut the other way, and they matter more on a side-effects page than the long list of benefits. In a 2026 study, MOTS-c blunted the reparative function of human mesenchymal stromal cells and, in a mouse model of renal artery stenosis, MOTS-c-pretreated cells failed to improve the kidney; the authors concluded it "may paradoxically exacerbate senescence and inflammation".12 And a 2018 review, relaying a recent report rather than its own experiment, says that in senescent cells MOTS-c, together with the related peptide humanin, exacerbated the senescence-associated secretory phenotype by stimulating secretion of pro-inflammatory cytokines such as IL-6 and tumor necrosis factor alpha; the review relays that finding rather than reporting its own experiment.13 Both are cell and animal findings, not human ones, but they are the clearest signals in these records that MOTS-c is not automatically benign.

Where doses appear, they are animal doses on animal schedules, with no way to carry them across to a person. In one acute lung injury model, MOTS-c was given at 5 mg/kg twice daily by intraperitoneal injection for six days before the lung insult (animal study, mice, intraperitoneal, PMID 31931370).14 That per-kilogram, intraperitoneal, six-day design is one short animal-study design with no established human equivalent. It is also worth naming what is absent: among the fetched studies there is no dedicated safety-pharmacology, dose-ranging, or dose-limiting-toxicity study of MOTS-c, dosing periods are short, and route matters, for example in a mouse colitis model injected MOTS-c eased the disease while native MOTS-c given by mouth produced no significant improvement, and the same group then reported that an orally administered MOTS-c analogue, a modified molecule rather than native MOTS-c, did ease the colitis, so what decided the result was the molecule as delivered, not the route alone,16 and peripherally administered MOTS-c does not cross the blood-brain barrier on its own.17

One concern worth heading off: because a mouse study reports that MOTS-c improved insulin sensitivity,22 a fair question is whether it could drive blood sugar too low. In the fetched animal work that did not appear. In a gestational-diabetes mouse model MOTS-c lowered elevated glucose therapeutically,22 and a PubMed search for MOTS-c and hypoglycemia, run in the research for this page, returned no studies. That is an absence of evidence in short animal experiments, not a safety guarantee in people.

Injection-site and online reports, not trial data

Search results for MOTS-c side effects are dominated by anecdote, and it needs to be labelled as such. The U.S. Anti-Doping Agency, describing people who buy the peptide online, reports "many reported side effects, including increased heart rate or heart palpitations, injection site irritation, insomnia, local or generalized immune reactions, and fever", and USADA itself frames these as anecdotal reports from people who say they buy it online, not trial findings.5 A commercial vendor writeup goes further and describes post-injection redness, swelling and mild irritation that it calls "usually harmless and fade quickly", plus mild digestive discomfort some users report, which is vendor and user-report content, not clinical data.20 Neither source is a controlled study, and the honest weight to give them is low.

There is a real, non-anecdotal risk in this picture, and it is about the product rather than the molecule. A 2026 Sports Medicine review places MOTS-c among unapproved peptides sold on a gray market that operates largely outside regulatory oversight.9 The FDA, in placing MOTS-c in its compounding category 2, warned that compounded MOTS-c "may pose significant risk for immunogenicity for certain routes of administration" and raised concerns about peptide-related impurities and API characterization.8 Those FDA concerns apply specifically to compounded MOTS-c products and do not establish the safety or toxicity of MOTS-c itself.

For MOTS-c, this page links to our supply partner, Peptara Labs.

Disclosure: Some links on this page are referral links. Peptides Vietnam may earn a fee at no cost to you. Editorial content is never sold.

The missing piece: no long-term human data

The single most important safety fact about MOTS-c is a gap. The longest human dosing found in the fetched sources is the four-week CB4211 Phase 1b course (trial dose, not a recommendation, CohBar Phase 1b company release), and that was an analog, with no peer-reviewed publication or registry results table, only company topline disclosures.12 Beyond it, no longer human dosing or safety follow-up appears in these sources. USADA states "it is unknown under what conditions (if any) it is safe to use MOTS-c because there are no completed human clinical trials".5 A research-foundation review is just as flat: "MOTS-c therapeutic safety has not been established", and it adds that MOTS-c has not been clinically tested in humans as a therapeutic peptide and that preclinical models have not thoroughly evaluated its safety.4 The FDA, quoted in that review, has said it has not identified any human exposure data on products containing MOTS-c by any route.4 A 2026 Sports Medicine review, surveying peptides sold this way, warns that "rigorous human safety data are scarce, and there is potential for serious harm to patients".9 None of that says MOTS-c is dangerous. It says the work needed to know has not been done.

Banned in sport, and not approved

Two status facts round out the picture. First, MOTS-c is banned in sport. According to USADA, a WADA signatory, MOTS-c is "prohibited at all times" on the WADA Prohibited List, classified under the hormone and metabolic modulators section as an activator of AMP-activated protein kinase.5 USADA notes it was added as an example to that section in the 2024 list, and it remained on the 2025 list.67 Anti-doping scientists took it seriously enough to build a validated mass-spectrometry assay to detect synthetic MOTS-c in plasma,18 and review papers had flagged it as a misuse risk years earlier.19

Second, it is not an approved medicine. USADA states MOTS-c is not approved by the FDA for use in humans or in compounded medications.5 The FDA placed it in category 2 of its compounding review, the tier for substances that may present significant safety risks,8 and a research-foundation review notes that since September 2023 the FDA has not allowed pharmacies to compound MOTS-c for human use.4 The regulatory read is consistent: an experimental compound, marketed ahead of its evidence, that the FDA has not approved for human use.

The short version

  • No completed human trial has ever dosed MOTS-c itself, so it has no established human side-effect profile.
  • The nearest human data is the CB4211 trial, a compound CohBar called a MOTS-c analog: injection site reactions were the main adverse event, put by CohBar at 79% versus 33% on placebo, with no serious adverse events reported and no peer-reviewed publication or registry results table, only company topline disclosures.
  • Animal and cell studies mostly report benefit, but a few show harm: in cells MOTS-c increased senescence and inflammatory markers, and MOTS-c-pretreated cells failed to improve renal outcomes in a mouse model.
  • The online side-effect lists (palpitations, injection-site irritation, insomnia, immune reactions, fever) are anecdotal self-experimenter reports, not trial data.
  • No long-term human safety data appears in the fetched sources; the longest reported human dosing is four weeks, of an analog (trial dose, not a recommendation, CohBar Phase 1b company release).
  • MOTS-c is prohibited in sport at all times and is not FDA approved; the FDA flags possible immunogenicity, peptide-related impurity, and API-characterization concerns for compounded MOTS-c, depending on the route.
  • No completed human trial has administered MOTS-c itself or tested a human microdosing schedule, so every figure here is study evidence, never a recommendation.

Frequently asked questions

Does MOTS-c have proven side effects in humans?+

Not in the way the question implies. No completed clinical trial has ever given MOTS-c itself to people and reported what happened, so there is no established human side-effect profile. The closest human data comes from CB4211, a compound its maker CohBar described as an analog of MOTS-c, whose Phase 1b study reported injection site reactions as the most common adverse event and no serious adverse events, though full results have not been disclosed. Everything else circulating as MOTS-c side effects comes from animal studies, cell studies, or anecdotal user reports, not from trials of the peptide in people.

What side effects showed up in the CB4211 trial?+

CB4211 is described by its maker as an analog of MOTS-c, not MOTS-c itself, and it was a short Phase 1 study, so read it as adjacent evidence. In its Phase 1b portion, the most common adverse events were transient, generally mild to moderate injection site reactions, reported by CohBar in 79% of people on CB4211 versus 33% on placebo, with no serious adverse events. The program had earlier been paused in 2018 over persistent painless injection-site bumps, and no results were posted to the trial registry as of the 2026-09-29 fetch.

What side effects do people report from buying MOTS-c online?+

Anti-doping and vendor sources list several, but all of them are anecdotal, not trial data. USADA reports that people who say they buy MOTS-c online describe increased heart rate or heart palpitations, injection site irritation, insomnia, local or generalized immune reactions, and fever, and USADA itself frames these as anecdotal reports from people who say they buy it online, not trial findings. A commercial vendor writeup adds injection-site redness and swelling it calls usually harmless, plus mild digestive discomfort. None of this is evidence from a controlled study.

Is there long-term safety data for MOTS-c?+

No. The longest human dosing in the fetched sources is the four-week CB4211 Phase 1b course (trial dose, not a recommendation, CohBar Phase 1b company release), and that was an analog, not MOTS-c. USADA states it is unknown whether MOTS-c is safe to use because there are no completed human clinical trials, a research foundation review says its therapeutic safety has not been established and it has not been clinically tested in humans as a therapeutic peptide, and the FDA has said it has not identified any human exposure data for MOTS-c by any route. No trial has tested any microdose or self-directed schedule either.

Is MOTS-c banned or FDA approved?+

It is banned in sport and it is not approved. According to USADA, MOTS-c is prohibited at all times on the WADA Prohibited List as an activator of AMP-activated protein kinase in the hormone and metabolic modulators class, and it is not approved by the FDA for use in humans or in compounded medications. The FDA placed MOTS-c in category 2 of its compounding review for possible significant safety risks, and since September 2023 has not allowed pharmacies to compound it for human use.

Sources and references

Every figure on this page traces to one of these sources, fetched on 2026-09-29. Numbers match the citation markers in the text.

  1. 1.ClinicalTrials.gov NCT03998514. Phase 1a/1b randomized, double-blind, placebo-controlled study of CB4211 in healthy non-obese subjects and subjects with NAFLD. Status completed, enrollment 88, no results table posted. Fetched 2026-09-29. clinicaltrials.gov / NCT03998514
  2. 2.CohBar, Inc. Announces Positive Topline Results from the Phase 1a/1b Study of CB4211 (GlobeNewswire, 2021-08-10). Company topline safety and tolerability summary and dose details. globenewswire.com / CohBar topline 2021
  3. 3.CohBar, Inc. Q2 2021 Investor Presentation, SEC EDGAR Exhibit 99.3, August 10, 2021. Reports the CB4211 Phase 1b injection site reaction incidence. sec.gov / CohBar Exhibit 99.3
  4. 4.Cognitive Vitality report on MOTS-c, Alzheimer's Drug Discovery Foundation, last updated September 17, 2025. Reviews the CB4211 trial history, FDA and USADA statements, and the state of MOTS-c safety evidence. alzdiscovery.org / MOTS-c report
  5. 5.U.S. Anti-Doping Agency, What is the MOTS-c peptide? dateModified 2026-08-07. Prohibited status, FDA approval status, and anecdotal user-reported side effects. usada.org / what is MOTS-c
  6. 6.U.S. Anti-Doping Agency, Explanation of Key Changes on the 2024 WADA Prohibited List. Notes MOTS-c added as an example to Section S4. usada.org / 2024 key changes
  7. 7.U.S. Anti-Doping Agency, Athlete Advisory: What's New on the 2025 WADA Prohibited List. Lists MOTSc as an AMPK activator example. usada.org / 2025 advisory
  8. 8.U.S. FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks. Places MOTS-c in category 2 and flags immunogenicity and impurity concerns. fda.gov / category 2 substances
  9. 9.PMID 41966639. Sports Med, 2026. Review: Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. pubmed.ncbi.nlm.nih.gov/41966639
  10. 10.PMID 32052315. 2020. Observational cohort in type 2 diabetics with revascularized coronary artery disease: beta-amyloid and MOTS-c as additive predictors of adverse outcome. MOTS-c measured, not administered. pubmed.ncbi.nlm.nih.gov/32052315
  11. 11.PMID 37285113. 2023. Mouse study: intrathecal MOTS-c in spared nerve injury neuropathic pain. The MOTS-c reference cited in the CB4211 trial registry. pubmed.ncbi.nlm.nih.gov/37285113
  12. 12.PMID 42324588. Inflamm Regen, 2026. MOTS-c activates metabolic signaling but blunts reparative function in human mesenchymal stromal cells, with a murine renal artery stenosis model. pubmed.ncbi.nlm.nih.gov/42324588
  13. 13.PMID 30058454. 2018. Review (Rejuvenation Res), Mitochondrial-Derived Peptides Exacerbate Senescence: relays a recent report that MOTS-c and humanin increased pro-inflammatory cytokine secretion in senescent cells. pubmed.ncbi.nlm.nih.gov/30058454
  14. 14.PMID 31931370. 2020. Mouse study: intraperitoneal MOTS-c against LPS-induced acute lung injury. pubmed.ncbi.nlm.nih.gov/31931370
  15. 15.PMID 39321430. 2024. Mouse and cell study: MOTS-c suppresses ovarian cancer without systemic toxicity in vivo. pubmed.ncbi.nlm.nih.gov/39321430
  16. 16.PMID 36528071. 2023. Orally administered MOTS-c analogue ameliorates colitis (mouse model): intraperitoneal MOTS-c ameliorated disease, oral native MOTS-c did not, and an orally administered MOTS-c analogue did. pubmed.ncbi.nlm.nih.gov/36528071
  17. 17.PMID 33861582. 2021. Mouse study: peripherally administered MOTS-c does not cross the blood-brain barrier without a cell-penetrating carrier. pubmed.ncbi.nlm.nih.gov/33861582
  18. 18.PMID 30394592. 2019. Doping-control methods paper: a validated mass-spectrometry assay to detect synthetic MOTS-c in human plasma under the WADA International Standard. pubmed.ncbi.nlm.nih.gov/30394592
  19. 19.PMID 26842585. 2016. Review of emerging agents affecting skeletal muscle and mitochondrial biogenesis; lists MOTS-c among compounds that could be misused by athletes. pubmed.ncbi.nlm.nih.gov/26842585
  20. 20.pepdose.com, MOTS-c Side Effects. Commercial peptide vendor writeup of anecdotal, user-reported side effects. Fetched 2026-09-29. Not clinical data. pepdose.com / mots-c-side-effects
  21. 21.PMID 33473109. 2021. Human and animal study: exercise induces endogenous MOTS-c in human skeletal muscle and circulation. pubmed.ncbi.nlm.nih.gov/33473109
  22. 22.PMID 34798268. 2022. Mouse model of gestational diabetes: MOTS-c lowered elevated glucose and protected pancreatic beta cells. pubmed.ncbi.nlm.nih.gov/34798268

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This guide is for educational purposes only and is not medical advice. It describes what published research, clinical registries, company disclosures and regulatory records say about MOTS-c; it is not an endorsement, a dose, or an instruction to use any compound. MOTS-c is an unapproved, experimental peptide with no established human safety profile and is prohibited in sport. Consult a qualified healthcare professional before making any decision about your health.

Sources

  1. 1.ClinicalTrials.gov NCT03998514
  2. 2.CohBar Phase 1a/1b topline release (2021)
  3. 3.CohBar Q2 2021 investor presentation (SEC Ex. 99.3)
  4. 4.Cognitive Vitality MOTS-c report (ADDF)
  5. 5.USADA, What is the MOTS-c peptide?
  6. 6.USADA, 2024 WADA Prohibited List key changes
  7. 7.USADA, 2025 WADA Prohibited List advisory
  8. 8.FDA, category 2 bulk substances (safety risks)
  9. 9.PubMed PMID 41966639
  10. 10.PubMed PMID 32052315
  11. 11.PubMed PMID 37285113
  12. 12.PubMed PMID 42324588
  13. 13.PubMed PMID 30058454
  14. 14.PubMed PMID 31931370
  15. 15.PubMed PMID 39321430
  16. 16.PubMed PMID 36528071
  17. 17.PubMed PMID 33861582
  18. 18.PubMed PMID 30394592
  19. 19.PubMed PMID 26842585
  20. 20.pepdose.com, MOTS-c Side Effects
  21. 21.PubMed PMID 33473109
  22. 22.PubMed PMID 34798268