MOTS-c Dosage and Side Effects: What Has Been Tested in People

No dose of MOTS-c has been tested in people, so there is no MOTS-c dosage to follow. FDA’s 2026 review found no human study of the peptide by any route and no animal toxicity studies either.^[2] The only randomized human trial with any results used CB4211, a modified version of MOTS-c, at 25 mg a day for four weeks in 11 people, and its results were announced by the company but never published.^[3][4] On October 28, 2026, HHS said it would not act against licensed pharmacies that compound MOTS-c acetate as an injection for an individual patient’s prescription.^[1] That policy sets no dose and is not an approval. Side effects of MOTS-c in people are undocumented. For the analog, the only side effect the company reported in more than 10% of people was injection-site reactions.

Is there a MOTS-c dosage chart that comes from a study?

No. The charts that rank for “MOTS-c dosage” come from peptide sellers and forums. They give milligrams per injection, weekly totals and on/off cycles, and they disagree with each other. None cites a human trial of MOTS-c, because none exists. FDA searched PubMed, Embase, the Cochrane library and ClinicalTrials.gov and found no clinical study, no pharmacokinetic data in people and no human exposure data for MOTS-c via any route.^[2]

A tested dose needs at least two things the MOTS-c record lacks. One is a measure of how much of the drug reaches the blood and how long it stays there; FDA found no such study in animals or people.^[2] The other is a comparison of several doses showing which one works and which one causes harm. FDA noted that the mouse studies “have not evaluated the dose-response relationships” for any effect.^[2]

The figures closest to MOTS-c dosing in the public record are these. The pharmacy that nominated MOTS-c to FDA proposed 5 mg and 10 mg vials for injection under the skin, which describes what it wanted to make, not a dose anyone tested.^[2] The analog CB4211 was given at 25 mg daily. And mice received 0.5 to 15 mg per kilogram of body weight, mostly injected into the abdominal cavity.^[2]

The one randomized trial used an analog, CB4211

HHS justified including MOTS-c in its policy partly by pointing to a randomized, placebo-controlled trial of a MOTS-c analog that it said reported no serious adverse events.^[1] The policy does not name the trial. On ClinicalTrials.gov the only randomized trial of a MOTS-c analog is CohBar’s phase 1a/1b study of CB4211, which the company called “a novel and improved analog of MOTS-c.”^[3][4] A PubMed search for CB4211 returns nothing, so everything known about the results comes from the registry entry and one company press release.

The registry lists 88 people enrolled and the trial as completed in April 2021, with no results posted.^[3] The company described 65 healthy adults in the first stage, used “to select the most appropriate dose” for the second, and 20 in the second.^[4] Its main measures were safety ones: adverse events, lab tests, heart tracings and injection-site reactions.^[3] People in the four-week part were required to live in the clinical unit for the whole treatment period, so they were watched far more closely than anyone injecting at home.^[4]

According to the company, there were no serious adverse events, and the only side effects seen in more than 10% of people on CB4211 in the four-week part were “transient and generally mild to moderate injection site reactions.”^[4] The company also reported falls in the liver enzymes ALT and AST and a 6% fall in blood glucose, with only “a trend towards lower body weight.”^[4] CohBar never ran a larger trial and announced in November 2023 that it would liquidate.^[10] Our MOTS-c evidence review covers those efficacy results and the company’s end in more detail.

Why CB4211’s 25 mg does not become a MOTS-c dose

CohBar described CB4211 as an improved analog, which means its structure was changed from the natural peptide. The company has not published how it was changed or how its potency and breakdown compare with the natural peptide. Twenty-five milligrams of one molecule does not tell you what 25 mg, or any amount, of the other will do.

That gap is wide for MOTS-c in particular. In a lab test, anti-doping chemists found that MOTS-c added to human blood was quickly cut into shorter fragments.^[8] FDA said it “remains to be determined” whether injecting MOTS-c into a person produces active levels of the peptide at all.^[2] A modified peptide can last longer or shorter in the body than the original, and nobody has published those numbers for either molecule.

HHS wrote that the analog trial reported no serious adverse events “at an exposure well above the compounded regimen.”^[1] The policy does not say what that regimen is, and no study has measured MOTS-c exposure in people, so the comparison cannot be checked. Four weeks in 11 closely monitored people also cannot detect uncommon or slow-developing harms.

Mouse doses, and why they cannot be scaled to a person

Almost all of these doses went into the abdominal cavity, a route people do not use. The amounts also vary thirtyfold between studies with no test of which dose was needed. That is part of why FDA said the mouse results “should be interpreted with caution.”^[2]

Vendor charts sometimes convert these mouse doses into a human-equivalent dose using a body-surface-area formula. That formula comes from FDA guidance for choosing the first dose in a first-in-human trial, and it starts from a specific number: the highest dose that caused no adverse effects in formal animal toxicity studies. The guidance says the calculation “should begin after the toxicity data have been analyzed” and that a safety factor “of at least 10” is then applied.^[5] MOTS-c has no such toxicity studies: FDA found no single-dose, repeat-dose, genetic, reproductive or cancer toxicity data.^[2] Converting an effective mouse dose skips the step the method exists to protect, and the result is a guess about benefit with no safety margin behind it.

Doses per week, cycles and timing

Searches for a weekly MOTS-c dose usually lead to charts with several injections a week and planned breaks of a few weeks. No published study tested a weekly total or an on/off cycle in people. The schedules that appear in the research record are short and specific:

• Once daily, for 7 days or 4 weeks, in the CB4211 trial, with a different molecule.^[3]
• Once or twice daily for days to 12 weeks in mice, mostly by injection into the abdominal cavity.^[2]
• Three times a week in very old mice in the 2021 lifespan experiment, at 15 mg/kg.^[2][7]

No credible trial of MOTS-c itself is registered: the one ClinicalTrials.gov listing comes from a sponsor whose TB-500 record opens with the words “This fictional study is an example of a ClinicalTrials.gov-style record.”^[9] Until there is real human data, every weekly plan is an extrapolation from mice or from a different molecule.

MOTS-c side effects: what is documented and what is not

Seller pages tend to list mild injection-site redness, fatigue, headache and nausea as MOTS-c side effects. None of those lists traces to a published study of MOTS-c in people. Here is what the record supports.

The immune question is the most specific risk FDA described. Peptides injected under the skin are more likely to provoke antibodies than those given into a vein, and clumped peptide or manufacturing impurities raise that chance.^[2] FDA’s briefing explains that antibodies against a peptide can cancel its effect and, in some cases, neutralize the activity of “the endogenous peptide counterpart,” meaning the version the body makes itself. MOTS-c is made naturally in mitochondria, so that possibility applies here, though it has never been tested.^[2]

The absence of adverse-event reports is also weak evidence of safety. FDA’s database held no MOTS-c reports, but the briefing notes that unless someone files a report, the agency “may not be aware” of problems with a 503A compounded product.^[2] The new HHS policy requires compounders to report serious adverse events, which should improve this if pharmacies comply.^[1] If you have a reaction, you or your prescriber can report it directly through FDA MedWatch.^[11]

If you take a GLP-1 drug, the blood-sugar question deserves attention before anything else. Our guide to adding peptides alongside a GLP-1 covers combination risks, and peptide blood work and monitoring covers what a prescriber might check.

What the October 2026 HHS policy allows for MOTS-c

MOTS-c is one of six peptides in the policy HHS issued on October 28, 2026. HHS said it does not intend to take enforcement action against state-licensed pharmacies, federal facilities or licensed physicians that compound these peptides under section 503A, as long as every condition in the policy is met. The policy is interim: it lasts until FDA finalizes a rule deciding whether each peptide goes on the 503A bulks list, and HHS said it may revisit the policy if a safety signal or quality problem appears.^[1]

Three points are easy to miss. First, the policy approves nothing; HHS itself says compounded drugs “are not FDA-approved,” and FDA does not review their safety or effectiveness.^[1] Second, it leaves the dose to the prescriber, who has no human MOTS-c study to base it on. Third, it does not cover research-use-only vials sold online; HHS framed the policy as a way to draw patients away from those.^[1] Our explainer on the HHS peptide compounding policy covers all six peptides, and 503A vs 503B pharmacies explains why only the first kind is included. Because of the single-ingredient rule, the MOTS-c blends some clinics sell fall outside the policy; see peptide blends and stacks.

The policy’s safety reasoning also differs from FDA’s own review five months earlier. HHS said the rodent studies showed metabolic benefit “without systemic toxicity.”^[1] FDA’s briefing found that no formal toxicity studies of MOTS-c had been done, and concluded that its potential safety risks in humans “are unknown.”^[2] Both statements can be accurate at once: the mouse studies were designed to look for benefit, and not finding obvious harm in them is a different thing from a toxicity study.

Questions to ask a prescriber before MOTS-c

• What dose are you prescribing, and what is it based on, given that no human MOTS-c dose study exists?
• Which pharmacy compounds it, is it a 503A pharmacy, and will it give me the certificate of analysis for the batch?
• Is it MOTS-c acetate alone, or a blend that falls outside the HHS policy?
• How will you check my blood sugar, especially if I take a GLP-1, insulin or metformin?
• What reaction should make me stop, and how do I report it?

Clinics that list MOTS-c are on our MOTS-c provider rankings, and the MOTS-c peptide profile covers how sellers present it. A prescription brings a clinician into the decision. Every MOTS-c dose prescribed today is still set without a human trial behind it. For the legal status of the peptides outside the HHS policy, see which peptides are legal.