I’m staring at a black-and-white body map for “subcutaneous injection sites” from a peptide clinic which, according to the word on the street, has just opened a “huge office in LA”. You won’t find the wellness clinic anywhere online; there’s only a random email to contact, and you have to be personally sent the multi-page “guide and suggested weekly schedule for preparing, dosing and administering peptides”. The entire doc feels entirely The Substance-coded – the logo appears to be a close-up of a molecule, and there are instructions for how (and how often) to administer the peptide vials, with .5ml of bacteriostatic water. The “treatment menu” is also extensive, including a BPC-157/GHK-Cu blend, a CJC/Ipamorelin blend, NAD+, Retatrutide, TB-500 and Tirzepatide. There are pseudo-scientific phrases throughout the menu too, like “deep rejuvenation”, “optimised ageing”, “longevity”, “cellular fuel”, “metabolic control” and “refining physique”, telling you what each peptide will do for your body – only no one, not even scientists, is entirely sure what some of these experimental peptides can and will do. This fact, however, hasn’t stopped fitness and fashion influencers from injecting themselves, conducting what is, in many cases, the first human trials at home.

You may have heard of the word “peptides”, short chains of amino acids which are essentially the “building blocks” of proteins (long chains of amino acids), in relation to skincare products, like Hailey Bieber’s Rhode peptide treatment. There are peptide serums, collagen peptide creams and glazing fluids, usually marketed under the framing of peptides being skin-plumping or having anti-ageing properties. But peptides aren’t exactly new: they have been used in medicines for about 100 years, including FDA-approved drugs like Enfuvirtide for HIV or Linaclotide for IBS. The semaglutides in newer anti-diabetic-turned-weight loss drugs, Ozempic and Wegovy, are also considered a peptide. After Ozempic came onto the market in 2017, the word “peptides” became a beauty and longevity buzzword, and other peptides involved in the production of growth hormones. Jennifer Aniston said she swears by weekly peptide injections, and Kourtney Kardashian Barker’s wellness brand, Poosh, published an article on ‘peptide therapy’. Recently, an online peptide market has emerged as part of the “bio-hacking” movement, where people sell drugs that were abandoned in early trials for either failing to show clear benefits or causing severe side effects.

Here’s another thing: some of the so-called “peptides” sold online in the peptide market aren’t even peptides. The company Warrior Labz SARMS received a warning letter from the FDA in 2022 for selling MK-677 with the label “for research purposes only” and “not for human consumption”, when it was clearly intended for human use. MK-677 is a non-peptide growth hormone. “Many of these so-called peptides were studied in isolation for boosting the secretion of growth hormone by the human body,” says Jonathan Jarry, science communicator at McGill University’s Office for Science and Society. “A lot of the ones that are popular right now on social media had studies that were abandoned because they failed to prove benefits, so the probability that there will be benefits is very low, but the risks of injecting yourself with something when you don’t know where it came from, who manufactured it or if it was contaminated are very real.” When it comes to drug development, Jarry adds that most molecules that seem like they might work for something turn out not to.

Let’s use NAD+ as an example of the layers of ongoing science that’s often ignored or over-exaggerated by peptide clinics. In our bodies, NAD+ plays a pivotal role in cellular metabolism and is a co-substrate for enzymes that play key roles in pathways that modify ageing. NAD+ peptide therapy, either at a spa or injected at home, however, is currently not scientifically backed up, says Shin-Ichiro Imai, an academic scientist who works in the field of ageing research and professor at Washington University School of Medicine. “If you check how many clinical trials have been conducted to precisely examine the safety and efficacy of NAD+ infusion therapy, it’s almost none,” he says. The starting point for NAD research goes back to the year 2000, when Imai and Leonard Guarente made the important discovery of enzymes called sirtuins. Imai’s lab was the first to report that our body loses NAD during the process of ageing, so the idea that spread is pretty simple: if NAD is an important compound for all living organisms and we lose it over time, why not supplement it?

Research on NAD+ is still relatively emerging. NAD+ is a compound that beauty influencers online are calling the secret to reversing ageing and achieving glowing skin; it’s available at many med spas. In 2014, Imai and Guarente published a paper outlining how supplementing NAD can improve age-associated functional defects, counteracting many diseases of ageing, including neurodegenerative diseases, something that’s so far been demonstrated in mice and rats but not humans. However, in the scramble to “age backwards” people are overlooking the science on how NAD actually breaks down in the body. While peptide clinics sell at-home NAD+ injections for hundreds of dollars, Imai says even if you put NAD+ directly into your blood circulation, it’s still extremely difficult to get into tissues or cells. “What’s bad about having a very high level of NAD+ in your blood is this: NAD can be consumed by many different enzymes, and one of them actually creates a very problematic compound that could do harm to your body,” he says. “Some people who have had NAD+ infusions have had very bad side effects; there haven’t been any tests on humans, but clinics are skipping this process.”

Adam Taylor, professor of anatomy at Lancaster Medical School, says that although peptides can have positive effects, not all peptides are created equal, and not everyone responds to peptides in the same way. “It is often the case that everything is OK, until it isn’t, and then people may be left out of pocket or with damage to their health,” he says. “As more is learnt about these emerging therapies, the risks and benefits will become clearer.” There’s also the illusion that anything injected, not taken orally, will work better. This isn’t the case for NAD+ – Imai says there have been a number of early clinical trials showing that taking NMN, a base that’s one step before NAD, orally can convert to NAD quickly in the body (again, which is something you don’t need to do). Imai “strongly opposes” NMN infusion for safety reasons, but it’s still something that’s starting to become available in the world of peptide therapies.

The rising popularity of weight loss peptides may be one reason why people are becoming more willing, and even eager, to inject themselves with peptides (even untested ones). It’s why people are promoting and selling unapproved GLP-1 drugs like Retatrutide on TikTok. “The idea that I can inject something to feel better and look better is totally an Ozempic outcome,” says Dr Melissa Doft, a double board-certified plastic surgeon in New York. Another is that people are falling into health-related conspiratorial circles online. After all, wellness clinics offering vitamins and treatments devoid of scientific backing have existed for years. “If these peptides were shown to work, they would become part of conventional medicine, but, unfortunately, what happens is there’s not enough evidence, so they become part of alternative medicine,” says Jarry. “People will often resort to conspiracy theories as to why doctors are not offering these things.

There’s also a deeper reason why “peptide stacking” is taking off right now: they’ve become associated with muscles, looksmaxxing and masculinity in a way that Jarry’s called “Goop for men”. By injecting yourself with something that doesn’t even have a name, it’s just a combination of letters and numbers (so manly!) in often black and white packaging, men are participating in wellness pursuits without the feeling of being frivolous. We’re currently living through a cultural return of the toxic alpha male online (just look at the raw meatfluencers), and some peptide stacks are being called “wolverine stacks”, marketed as an alternative to performance-enhancing drugs with claims like “heightmaxxing” (helping you grow taller). “I suspect there’s an appeal to peptides because they are not steroids and many of these peptides are branded as ways to naturally increase your body’s production of growth hormone,” says Jarry. “I think people can be easily reassured by the appeal to nature; if something has the coating of it being natural, people think it must be safe.” The reality is that just because something is already in your body, it doesn’t mean you should inject more of it.

Peptide stacking, therapy or at-home injections may have taken off on the manosphere, where so-called “clinics” with black market sites can move to a different URL to skirt FDA regulations, but injecting yourself with unapproved substances has now become part of how wellness culture is evolving more generally. It’s taking the beauty world’s problem with pushing questionable gummy or capsule supplements to the next level – when you inject yourself with anything, you are bypassing some of the body’s natural defences. By making a peptide trend with bold and unsubstantiated claims, beauty and wellness clinics can continue to sell back to us things that we naturally contain in multitudes. “It’s all about marketing, right? That’s why there’s such a craze for peptides right now,” says Jarry. “When life is built around peptides, we already have plenty of peptides in our bodies.”