Sermorelin + MOTS-c Stack: Safety and Monitoring Guide

What is actually known about each peptide?

Sermorelin is a 29-amino-acid analogue of human growth hormone-releasing hormone (GHRH) that prompts the pituitary to release the body's own growth hormone; it is not growth hormone [7]. MOTS-c (mitochondrial open reading frame of the 12S rRNA-c) is a 16-amino-acid peptide encoded in mitochondrial DNA, first reported in 2015 [8].

The two peptides are in very different positions. Sermorelin has a pediatric treatment trial, short adult physiology studies and a regulatory history that ended in withdrawal. MOTS-c has no human dosing of any kind in the published record [1].

Is there any human safety data for MOTS-c?

No. FDA searched PubMed, Embase, the Cochrane library and other sources and found no clinical study in which MOTS-c was given to people; the 12 papers the nominator cited were not clinical studies [1]. A search of FDA's adverse-event database through March 9, 2025 retrieved no MOTS-c reports [1]. FDA also found no animal toxicity studies, no pharmacokinetic data in humans or live animals, and no human exposure data by any route of administration [1][2].

What exists is cell and rodent work. In mice, injected MOTS-c reduced weight gain on a high-fat diet (about 20% lower body weight after 8 weeks at 0.5 mg/kg/day intraperitoneal), improved insulin sensitivity and exercise performance, and in one study a late-life schedule of 15 mg/kg three times weekly from 23.5 months of age lengthened median lifespan from 912 to 970 days [1][8][9]. FDA noted that no dose-response relationships were assessed and that the molecular targets are unknown [1].

Even the basic kinetics of an injection are unsettled. In vitro, MOTS-c is quickly broken down in human blood, which raises the question of whether injecting it can produce active levels in a person [1]. In humans, exercise raises the body's own MOTS-c in muscle and blood [9]; one randomized study of 30 healthy adults found circulating MOTS-c showed only a trend to rise after endurance exercise [10]. That is a measurement of natural levels, not of an injected dose.

The specific concern FDA raised for the injected form is immunogenicity, an immune reaction driven by peptide aggregation and related impurities; MOTS-c has no immunogenicity data [1][2]. Separately, the nomination FDA reviewed proposed 5 mg and 10 mg subcutaneous injections, and there is no approved dose and no human dosing study [1].

What does sermorelin's human record show?

Sermorelin was approved as Geref for two uses only: a diagnostic test of pituitary growth hormone reserve (NDA 019863, approved 1990) and treatment of idiopathic growth hormone deficiency in children with growth failure (NDA 020443, approved 1997) [4]. It was never approved for adults, anti-aging, weight loss or athletic performance [4]. The manufacturer discontinued it in 2008 and FDA withdrew both approvals effective June 18, 2009 [4]. In March 2013 FDA determined that Geref was not withdrawn for reasons of safety or effectiveness [4].

The main safety dataset is the one-year open-label pediatric trial: 110 previously untreated prepubertal children with growth hormone deficiency received 30 micrograms/kg subcutaneously at bedtime, and 86 were evaluable for efficacy [3]. No adverse changes in general biochemical or hormonal analyses were noted, fasting glucose did not change, IGF-I was not excessively raised, and the peptide was well tolerated overall [3].

The adult data are physiology, not outcomes. Ten healthy older men (mean age 68) took 0.5 mg and 1 mg subcutaneously twice daily for 14 days each in random order; at the high dose, 24-hour growth hormone and IGF-I rose to levels not significantly different from nine young men (mean age 26) [5]. After an intravenous dose in healthy men, sermorelin was eliminated quickly yet growth hormone stayed elevated for about 3 hours [11].

Which labs would a monitoring plan rest on?

For sermorelin, the studies cited here reported IGF-I in both the pediatric and the older-men work, and fasting glucose in the pediatric trial [3][5]. In the one-year pediatric study, IGF-I was not excessively generated and fasting glucose was unchanged [3]. On the question of pituitary suppression, one study of 30 healthy men aged 19 to 43 found that three intranasal doses of GHRH(1-29) in one day did not suppress growth hormone secretion that night; that result does not establish the effects of other doses, durations or routes [11].

There is no equivalent list for MOTS-c. With no human dosing study, no laboratory marker has been shown to track its effect or its risk [1]. Any MOTS-c monitoring panel would have to be extrapolated from mouse data, not from measured human outcomes.

Does stacking them change either risk?

No human study has given MOTS-c, alone or together with sermorelin [1]. Sermorelin raises growth hormone and IGF-I in people [5]; MOTS-c improved insulin sensitivity in mice [8][9]. Whether those effects interact in a person cannot be described from any published measurement, and no combination has been tested for additive toxicity.

It is also not possible to conclude that the pair is safer than either peptide alone. FDA found no human exposure data for MOTS-c and its adverse-event search retrieved no reports [1], so there is no human safety record for MOTS-c in either direction.

Regulatory status of each peptide

Sermorelin is not listed on FDA's page of bulk substances that may raise significant safety risks when compounded (content dated 04/22/2026) [2]. On FDA's list of nominated substances for outsourcing facilities (updated March 21, 2025), sermorelin acetate is in category 1 and carries the list's symbol for substances that are components of FDA-approved drugs [12]. It does not appear in any category on FDA's list for state-licensed pharmacies and physicians (updated May 14, 2026), and it is not one of the six peptides in HHS's October 2026 draft enforcement-discretion policy [13][14]. With Geref off the market, US sermorelin products are compounded, and compounded drugs are not FDA-approved [15].

MOTS-c is not an FDA-approved drug and is not a component of one; FDA's 2026 review found no USP or National Formulary monograph, no listing in the European or Japanese pharmacopeias and no product authorized by the European Medicines Agency [1]. It sits in the 'nominated but withdrawn' table of FDA's safety-risk page, where FDA cited the absence of human exposure data, missing safety information, and immunogenicity risk from aggregation and impurities; removal from category 2 was not a finding that it is safe [2]. It appears in none of the three categories on FDA's list for state-licensed pharmacies or on the outsourcing-facility list, so FDA's category 1 policy does not cover it [13][12][16].

Two later events do not change that. On July 23, 2026 the Pharmacy Compounding Advisory Committee voted in favor of adding MOTS-c to the bulks list, against FDA staff's recommendation; that advice is not binding and adding it would take formal rulemaking [17][15]. HHS's draft policy filed in October 2026 names MOTS-c acetate for subcutaneous or intramuscular injection and says HHS does not intend to take enforcement action against certain state-licensed pharmacies, federal facilities or licensed physicians if its conditions are met — a draft statement that is not binding and not an approval [15][14].

Sport

Both peptides are named on WADA's Prohibited List. Sermorelin is in S2.2.4 (growth hormone releasing factors), MOTS-c in S4.4.1 (activators of AMP-activated protein kinase); both are prohibited at all times, in and out of competition, and both are on the 2026 List and the 2027 List [6][18].