A 16-amino-acid peptide that the body's own mitochondria encode, which rises with exercise and helps muscle handle fuel. Synthetic versions sold online borrow from mouse studies showing better endurance and insulin sensitivity, but the first controlled human trial of the injected peptide only began recruiting in 2026, and the FDA has flagged compounded MOTS-c as a safety risk.
Most peptides are encoded in the cell nucleus, but MOTS-c is written into mitochondrial DNA, inside the gene for the 12S ribosomal RNA. Its main target seems to be skeletal muscle, where it blocks part of the folate cycle and the purine-building pathway tied to it. That metabolic squeeze switches on AMPK, the enzyme cells use to sense low energy, which raises glucose uptake and fat burning much as exercise does. Under stress the peptide can also act on nuclear genes for metabolism and protein quality control.
Injected peptide (1/6)
MOTS-c, a copy of a 16-amino-acid peptide our mitochondria make, is injected.
In mice, that pathway translated into resistance to high-fat-diet obesity and insulin resistance, and intermittent treatment started late in life increased physical capacity and healthspan. In humans, a single bout of endurance cycling raised circulating mitochondrial peptides, with MOTS-c showing a trend upward, while resistance exercise did not. Blood levels of the natural peptide correlate with insulin sensitivity in lean people but not in obese people. Whether injected synthetic peptide reaches muscle and does the same job in a human is exactly what remains untested.
MOTS-c is sold online for weight loss, exercise performance, blood sugar, and longevity. In mice, injected MOTS-c prevented age-related and diet-induced insulin resistance and obesity, and it improved physical performance in young, middle-aged, and old animals. In people, the research so far has measured the body's own MOTS-c in blood: levels rise after endurance exercise, run lower in type 2 diabetes, and track insulin sensitivity in lean adults. None of that tells you what injecting it does to a person.
The first randomized, placebo-controlled trial of synthetic MOTS-c in humans, a 12-week phase 2a study in adults with prediabetes and excess weight, began recruiting in 2026 and has no results yet. Everything sold today predates that trial and comes from research-chemical vendors or compounders. The FDA has found no human exposure data for compounded MOTS-c and says it lacks the information to know whether it would harm people. The World Anti-Doping Agency lists MOTS-c among prohibited metabolic modulators.
The evidence base is a mix of mouse pharmacology and human biomarker studies. The founding 2015 paper and a 2021 follow-up showed metabolic and performance benefits in mice, and a meta-analysis of 602 participants found plasma MOTS-c lower in type 2 diabetes but, after subgrouping, higher in obesity. A human exercise study randomized subjects to endurance cycling, resistance exercise, or control and found that only endurance exercise raised circulating mitochondrial peptides. No human trial of synthetic MOTS-c has reported results.
The biggest gap is the absence of any controlled trial of the injected peptide, which the 2026 prediabetes study is the first to attempt. How much synthetic peptide survives injection, reaches muscle, and acts there is unmeasured in people. Biomarker studies cannot be read as evidence that a product works, since they measure the body's own peptide. Products sold online have no verified identity or purity, and the FDA's compounding review found no human safety information at all.
No human safety data for injected MOTS-c have been published, so its side effects are unknown. The FDA states it has identified no human exposure data for compounded MOTS-c and that compounded versions may pose a significant risk of immune reactions along with impurity and characterization problems. The mouse studies did not report toxicity, but they were not designed to find it. The phase 2a trial now recruiting follows participants for safety through week 16.
No regulator has approved this compound, and no company is seeking approval.
MOTS-c is not approved by the FDA or any other regulator. The FDA lists compounded drugs containing MOTS-c among bulk substances that may present significant safety risks, and its Pharmacy Compounding Advisory Committee is scheduled to discuss MOTS-c free base and acetate on July 23, 2026, which is a review and not an approval. The World Anti-Doping Agency names MOTS-c among prohibited metabolic modulators. Health Canada lists it among unauthorized injectable peptides it has seized.