Whether you’re involved in the world of wellness, follow celebrity culture or simply get served anti-ageing content by the algorithm, there’s a good chance you’ll have come into contact with the latest fad spreading across the US and beyond: peptides.
This broad-brush term that describes short chains of amino acids – which, technically, includes anything from insulin to GLP-1s like Ozempic – is taking on a new meaning among thousands of influencers and those who follow them.
With reported benefits ranging from weight loss to better sleep, injury prevention and even enhanced libido, more and more people are turning to these compounds to improve their lives, feel younger and live longer.
But be warned. The peptide world, which usually involves the purchase of injectable, unregulated substances from the internet, is chock-full of caveats. Some undoubtedly provide benefits. But how can you tell which ones they are? And what about the ones that don’t?
Peptides: The evidence
Lumping all peptides into one group is about as useful as discussing the health benefits of food.
Broadly, these molecules act as biological signals, triggering specific actions in cells and tissues. They sit, structurally speaking, between individual amino acids and full proteins: specific enough to have a defined function, small enough to be synthesised and sold online.
The compounds currently sweeping wellness communities seemingly boast a wide range of potential uses. BPC-157, a gastric peptide naturally produced in the stomach, is touted for injury healing and recovery. GHK-Cu, a copper peptide, is claimed to have anti-ageing effects on skin. TB-500 is marketed alongside BPC-157 in injury ‘recovery stacks’ (combinations of therapies or drugs).
The craze has spread far enough that, in San Francisco, people are reportedly attending so-called ‘peptide raves’ – social events centred on communal self-injection.
But if you came to this space hoping for solid science, prepare to be disappointed.
BPC-157, for example, is often held up as the poster child of the peptide movement, supposedly having the strongest evidence base among the current wave. Yet even that, on inspection, amounts to almost nothing.
“I am shocked by how bad the evidence is,” says Dr Andrew Steele, director of The Longevity Initiative. “I thought it was going to be shaky, but there is just absolutely nothing here.“
While animal trials have shown that BPC-157 likely has significant benefits, including enhanced injury recovery and the promotion of blood vessel growth (known as ‘angiogenesis’), trials in humans are distinctly lacking.
According to a 2025 review of the peptide, studies in humans amount to little more than asking people months after receiving BPC-157 whether their knee or bladder pain had subsided. No control groups were used in the research, nor was BPC-157 tested against a placebo.
Research into other peptides is similarly scant, and beyond the evidence vacuum lies some serious safety concerns.
Take TB-500, for example – another peptide known to promote angiogenesis which is commonly used by athletes and body builders to aid muscle growth and recovery. It’s a synthetic fragment of a naturally occurring peptide called thymosin beta-4, which has been linked in studies to colorectal and pancreatic tumour growth.
“TB500 is another tissue healing peptide, a bit like BPC-157,“ Steele says. “One of the big hurdles a tumour has to overcome is that as cells grow very quickly, they often grow so fast that they do not have a good enough blood supply. [What that means is] if you take a peptide that improves angiogenesis, you might be giving cancer a leg up.”
So, while there’s no evidence that TB-500 and BPC-157 directly cause cancer, anyone using them with a tumour already lurking inside them could potentially be promoting its growth – a credible concern given the biology, according to Steele.
Then there's Melanotan II – an artificial peptide that stimulates pigment cells in the skin to produce melanin and make users look more tanned.
According to Cancer Research UK, “melanotan nasal sprays and injections are not safe to use“, and clinical case reports have linked its use to skin cancer, including melanoma.
What’s in the tin?
Whether these compounds do what they say on the tin is one problem. What else is in the tin is quite another.
Because peptides are often sold as research chemicals rather than medicines, they’re entirely exempt from pharmaceutical regulation.
A private testing study found around 8 per cent of sampled peptide products contained bacterial endotoxins – contaminating substances introduced during the manufacturing process that go undetected by standard purity testing.
“There are just so many red flags around these peptides, even if we knew they worked,“ Steele says. “Buying a research-grade one off someone on the internet might be good enough for use in a lab, but is it good enough to stick in your body?“
This isn’t abstract. In July 2025, two women were hospitalised at RAADFEST, a Las Vegas anti-ageing festival, after receiving peptide injections from a physician specialising in ‘age reversal’ therapies. Both developed swollen tongues, breathing difficulties and elevated heart rates.
The exact compounds involved remain unknown, but the saga is a poignant reminder of the risks involved in seeking unregulated medical treatments.
This one (or two) might work
There are two exceptions worth separating from the rest.
Copper peptides – known as GHK-Cu – do have genuine clinical backing, but only for topical use on skin.
Research has found they stimulate collagen and elastin production, reduce inflammation and act as antioxidants.
Clinical trials and lab studies broadly confirm these benefits, making them one of the better-evidenced anti-ageing skincare ingredients available.
They can cause mild skin irritation in some people, but the risk profile for a face cream is a world apart from an injected research chemical.
And then there are the glucagon-like peptide-1sƒ (GLP-1s), which is one corner of the peptide world where the science really holds up. Semaglutide, sold as Ozempic and Wegovy, is technically a peptide, and its high-profile success may have helped fuel the broader craze, leading many to assume that other peptides available online must carry similar promise. They don’t.
But GLP-1s are rigorously trialled, regulated medicines. Beyond weight loss, emerging evidence suggests they reduce cardiovascular and possibly dementia risk through mechanisms that may include direct anti-inflammatory effects.
“The GLP-1s could be longevity drugs in an indirect way because they probably slow down ageing through weight loss,” Steele says. “But they might also be anti-ageing in a broader sense because they probably have various anti-inflammatory properties.”
And it’s likely, he adds, there are many other peptides out there with untapped anti-ageing potential.
“I would be shocked if there are no anti-ageing longevity peptides out there. But the problem is we do not have the evidence for any of the ones that exist now.”
In short, ‘peptide’ is a broad term for a smorgasbord of compounds that don’t neatly fit any box. Some are lifesaving medicines. Some are unproven. Some may be actively dangerous.
The general rule: if it requires a prescription, it’s probably there for a reason. If it arrives as a white powder or liquid in a vial from the internet, treat it with caution.
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