Peptides — What Works, What Is Legal, What to Avoid

Hydrolysed collagen is just collagen protein broken into small, easily absorbed peptides, and it is a legitimate over-the-counter supplement. The evidence is genuinely reasonable for skin elasticity and hydration, and there is some support for joint comfort and tendon or ligament recovery, especially when taken with vitamin C around loading. What it does not do is build muscle any better than a good complete protein — collagen is a poor muscle-building protein because it lacks enough leucine. Treat it as a targeted connective-tissue and skin supplement, not a mass-builder.

When a label boasts "whey peptides" or "hydrolysed protein", it simply means the protein has been partly broken into peptides so it digests and absorbs a little faster. It is real, safe and food-form, and it works exactly as well as ordinary quality protein for building muscle — the faster absorption is a minor, mostly irrelevant edge for most people, and hydrolysates cost more. This is the one place "peptides" on a supplement label is completely honest and completely unremarkable.

GLP-1 and dual GLP-1/GIP receptor agonists such as semaglutide (Wegovy, Ozempic) and tirzepatide (Mounjaro) are the one peptide class that reliably and powerfully changes body composition, with large trials behind them. That is exactly why they are licensed prescription medicines that must be assessed, prescribed and monitored by a clinician: they have real side effects, need dose titration, and are not appropriate for everyone. The vials sold online without a prescription are a different and dangerous world — frequently underdosed, mislabelled or counterfeit, with no medical oversight. The drug is real; buying it off a website is not the way to use it.

Bremelanotide (PT-141) is a melanocortin-receptor peptide licensed in the US as an on-demand treatment for low sexual desire in some women, so unlike the "research" peptides it does have a genuine medical identity. It can raise blood pressure and cause nausea and flushing, which is precisely why it belongs under a prescriber, not on a self-injected schedule from an unregulated vial. It is not licensed as a medicine in the UK at all, so any use would be a specialist off-label decision — certainly not an over-the-counter supplement.

BPC-157 is genuinely interesting in preclinical work — rodent studies show tendon, muscle and gut healing effects — which is why it is everywhere online. But there are essentially no published human trials proving it is safe or effective, its long-term safety is unknown, and it is not a licensed medicine anywhere. In the UK it cannot legally be sold for human consumption and is marketed as a "research chemical not for human use", and WADA added it to the banned list in 2022. Interesting science is not the same as a proven, legal product you should be injecting.

TB-500 is a synthetic version of a fragment of thymosin beta-4, promoted for tissue repair and recovery, usually paired with BPC-157. As with BPC-157, the supportive evidence is preclinical and animal-based, human trials proving benefit and safety are lacking, and it is not a licensed medicine. It is sold as a research chemical rather than a product for human use, and it is prohibited in sport by WADA. The marketing is confident; the human evidence is not there.

Growth-hormone secretagogues such as ipamorelin, CJC-1295, sermorelin and the GHRP family do genuinely stimulate your pituitary to release more growth hormone, so they are not inert. But raising GH and IGF-1 is not a free lunch — it can affect blood sugar, cause water retention and joint aches, and the physique benefits people are sold have not been shown to outweigh the risks in healthy adults. They are unlicensed for this use, sold as research chemicals, and prohibited in sport. Manipulating your endocrine system from an unregulated vial without monitoring is a genuinely risky thing to do.

IGF-1 LR3 is a modified, long-acting version of insulin-like growth factor 1, a powerful growth factor. It is emphatically not a casual supplement: growth-factor manipulation carries serious theoretical risks, including effects on blood sugar and concerns about promoting abnormal cell growth, and there is no safe, evidence-based self-dosing protocol for physique use. It is unlicensed, sold as a research chemical, and banned in sport. This is among the least sensible things in the whole peptide space to self-source.

GHK-Cu is a copper-binding peptide used topically in serums, with some reasonable evidence for skin appearance and wound-related benefits when applied to the skin. As a low-risk cosmetic ingredient it is a fair enough thing to try in a serum. What it is not is a fitness, recovery or muscle peptide, and the injectable versions sold for those purposes fall back into the unlicensed research-chemical category with none of the topical evidence to support them.

Melanotan II is an injectable peptide used to darken skin, and it is one of the few peptides the UK medicines regulator (the MHRA) has issued specific safety warnings about. It is unlicensed, its purity and contents from grey-market sellers are unknown, and reported effects include nausea, blood-pressure changes and concerns about changes to moles and skin lesions. There is no version of this that counts as a sensible supplement decision.