Chains of amino acids too short to count as full-fledged proteins. Peptides are an important class of drugs: almost 100 are approved as medicines, including insulin, human growth hormone and GLP-1, the active principle of Wegovy (a weight-loss drug made by Novo Nordisk) and Ozempic (a treatment for type-2 diabetes).
BPC-157 and TB-500 are two peptides popular among athletes seeking rapid recovery from bone fractures and torn ligaments, and increasingly among older men pursuing "anti-ageing" and general well-being. BPC-157 is a fragment of a stomach protein; TB-500 is a fragment of thymosin beta-4, a protein found in most body cells. Both act as signalling molecules. Animal experiments demonstrate that both promote wound healing and blood-vessel formation and reduce inflammation, without flagging worrying side-effects.
Human studies are scarce. A recent review found only three small ones for BPC-157, one of which suggested possible relief for chronic knee pain. Although thymosin beta-4 is the subject of promising trials for heart-attack recovery and corneal problems, TB-500 itself is not. Users usually administer the stack by injection.
No jurisdiction has approved the compounds as medicines, but few ban their sale; they can be marketed as "experimental chemicals" so long as no medical claims are made. Professional sports bodies, including the World Anti-Doping Agency, ban them. A "folk pharmacology" has developed on internet forums, where users swap tips, warn of side-effects and run informal product-testing laboratories to sort the wheat from the chaff.
Peptides are generally legal to sell in many rich countries via a loophole: they can be marketed as "research chemicals" labelled as not for human use. Sellers offer syringes, sterilised water and video injection instructions alongside the compounds. A study of 27 grey-market peptide samples carried out in Belgium and published in 2018 found purity levels ranging from 5% to 99.9%; six vials exceeded the legal maximum for arsenic and one for lead.
The grey market extends well beyond BPC-157. ACE-031 is said to boost muscle by inhibiting myostatin. Ipamorelin is a "secretagogue" designed to boost the body's production of human growth hormone (HGH); side-effects of excess HGH include heart disease, elevated cancer risk and acromegaly. Retatrutide, a weight-loss drug made by Eli Lilly and still in clinical trials, is widely available from unlicensed sellers. PT-141, otherwise known as bremelanotide, has been through clinical trials and is prescribed to pre-menopausal women to boost libido. BPC-157 may encourage angiogenesis—the creation of new blood vessels—which could encourage tumour growth as well as tissue repair.
A 2025 study by Luke Turnock, a criminologist at the University of Leicester, and Evelyn Hearne, a public health researcher at Liverpool John Moores University, found that many peptide users were dissatisfied with conventional medicine's response to diffuse symptoms like brain fog, fatigue and low mood, and turned to peptides as alternatives. A January survey by LloydsPharmacy found that 28% of respondents had bought GLP-1 drugs from unlicensed websites or social-media sellers.
In August 2025 Health Canada announced the seizure of drugs sold by the firm Canada Peptide. In September 2025 the European Medicines Agency issued a public warning about grey-market GLP-1 drugs, ordering product withdrawals and speaking of "cross-border collaboration with enforcement officers" and website blocking. Britain's medicines regulator has shut down two manufacturing sites suspected of making illegal weight-loss drugs.
On February 27th 2026, Robert F. Kennedy Jr, America's health secretary, announced on Joe Rogan's podcast his intention to allow 14 peptides to be prepared by licensed compounding pharmacies on prescription. Kennedy had earlier declared the American drug regulator's "war on public health is about to end", promising to halt its "aggressive suppression" of peptides and other fringe medicines.
In the absence of clinical oversight, cautious peptide users turn to direct-to-consumer blood-testing firms. SiPhox Health, a startup in Massachusetts, has developed a painless blood-draw device and markets its services to "high performers, biohackers, and athletes". Function Health, a firm in Austin, tracks dozens of biomarkers for upwards of $365 per year; its celebrity backers include Matt Damon and it was valued at $2.5bn in a fundraising round in November 2025.
A chicken is an egg's way of producing more eggs.