Introduction

Unapproved peptides are everywhere right now. Wellness influencers, men’s health clinics and online sellers all promote these synthetic amino acid chains for uses ranging from building muscle to boosting cognition to enhancing tans. Estimates suggest hundreds of thousands of people already inject them. Some vials sell for hundreds of pounds online. Yet regulators have not approved the vast majority of these products. Human clinical trials on their safety and efficacy barely exist. And regulatory changes in the United States could soon make grey-market peptides even easier to obtain.

What Are Unapproved Peptides?

Not all peptides carry the same level of risk or the same regulatory status. It helps to know the difference.

Regulators have fully approved certain therapeutic peptides. These include glucagon-like peptide-1 (GLP-1) receptor agonists such as semaglutide, which doctors prescribe for type 2 diabetes and obesity, as well as insulin. These compounds went through rigorous clinical testing before reaching patients.

Peptides also appear in cosmetics and dietary supplements, such as collagen and creatine. These occupy a different and less tightly regulated category.

Then there is the grey market. Sellers place disclaimers such as “for research purposes only” or “not for human use” on their websites. At the same time, they describe their products using words like “healing,” “regenerative” and “cosmetic.” No medicines regulator has approved these substances for human use. The clinical evidence for their safety or effectiveness is largely absent.

The Science Behind the Hype

Grey-market sellers have latched onto a genuinely promising area of research: mitochondrial-derived microproteins, or MDPs. Scientists previously called these mitochondrial-derived peptides, and the acronym MDP still applies.

Dr Pinchas Cohen and his team at the USC Leonard Davis School of Gerontology have identified at least 10 MDPs over the past 25 years, with five more expected for publication this year. His team currently tests hundreds of other compounds for potential biological roles. In preclinical trials, researchers are exploring whether MDPs could help address diabetes, sarcopenia, metabolic syndrome, cancer, Parkinson’s disease and Alzheimer’s disease.

One MDP called MOTS-c has progressed to a phase 1b clinical trial. Researchers now seek funding to push it towards full approval. The grey-market version of MOTS-c is a different story. Manufacturers in China produce it cheaply, and it represents a very early iteration of the molecule. Its half-life is only around 30 minutes. Whether it resembles the compound under study in research settings is a serious open question.

Early-stage lab research is not the same as a proven treatment. That gap matters enormously.

Why Unapproved Peptides Are a Public Health Concern

The risks of grey-market peptides go well beyond the question of whether they actually work.

Buyers cannot verify product quality. No independent body routinely tests these products for accuracy or purity. Purchasers have no reliable way to know whether what they inject is sterile, correctly dosed or even contains what the label states.

Nobody has studied peptide combinations. Many users inject “stacks,” meaning they combine multiple peptides in one session. Dr Eric Topol of the Scripps Research Translational Institute has publicly warned that no studies exist on the safety of mixing these substances. Yet the practice keeps growing.

Clinical evidence is absent. Researchers have not conducted meaningful clinical trials of grey-market peptides in humans. Dr Cohen has proposed creating a user registry to gather real-world outcome data, given the complete absence of formal research.

BPC-157, or Body Protection Compound-157, stands out as one of the most popular grey-market peptides. Scientists isolated it from gastric secretions rather than any food source. Estimates suggest hundreds of thousands of people currently inject it. Its safety and efficacy remain unclear.

Regulatory Changes on the Horizon

The regulatory landscape around unapproved peptides is shifting. In 2023, the US Food and Drug Administration (FDA) banned compounding pharmacies from using most grey-market peptides, citing significant safety risks. Then in April 2025, the FDA removed a dozen of these substances from its list of compounds raising serious safety concerns. New scientific evidence did not drive that decision. The parties who had originally nominated the peptides for compounding simply withdrew their requests.

Patient safety organisations ECRI and the Institute for Safe Medication Practices flagged this clearly. Their joint white paper stated that the removal was “not accompanied by or the result of new scientific evidence.”

The FDA’s Pharmacy Compounding Advisory Committee now plans to meet in late July and again before February to discuss reinstating these compounds on to the approved list for compounders. Separately, moves are under way to classify grey-market peptides as dietary supplements. That category carries considerably weaker regulatory oversight than approved medicines.

Looser rules do not produce safer products. They produce more widely available products whose safety nobody has properly established.

What This Means for Consumers

The appeal of peptides is easy to understand. People want better recovery, stronger physical performance and improved wellbeing. Legitimate researchers are genuinely investigating MDPs for serious diseases. That work deserves attention.

But a meaningful gap exists between early-stage laboratory research and a product someone can safely inject at home. Injecting substances of unknown purity, in unproven doses, alongside other untested compounds, carries real risks. The scientific-sounding name on a vial does not change that.

Staying critical of marketing claims and understanding the difference between preclinical research and proven medicine are among the most important steps anyone can take to protect their health.

Source: jamanetwork