Why health experts are concerned about the rise of peptides

Peptide may not yet be the 2026 Oxford Word of the Year, but it must surely be in the running.

From your friendly neighbourhood influencer, to the gym bros, injectable peptides have been all over social media and are now making mainstream news when things go horribly wrong.

People are taking them, and promoting them, for a seemingly endless list of reasons. Depending on who you ask, they’ll either put a pep in your step, give you a tan, make your skin glow, or even build you bigger muscles.

But for those of us not immersed in this new form of chemical pop culture, what the heck are they?

They’re chemical messengers

Many peptides occur naturally in the body (endogenous), or in the food we eat (exogenous). These short chains of amino acids are smaller than proteins and are entirely natural.

However, the peptides created in labs for varied purposes are synthetic.

Within the body, peptides act as precision chemical messengers regulating critical processes such as metabolism, growth, immunity, and tissue repair and building.

They are water-soluble, so they cannot pass directly through cell membranes. Instead, they bind to receptors on the surface of target cells to trigger a cascade of events inside the cell.

Some key categories of peptides include:

Some commonly used medicines are peptides

Some peptide medicines are familiar and legitimate: insulin, for example, is a peptide hormone with a long history of clinical use.

People are now taking peptides for a variety of reasons, including weight loss – such as with glucagon-like peptide-1 (GLP-1) receptor agonists which suppress hunger and slow down the functioning of the stomach.

These peptides have become commonly prescribed for diabetes control or weight loss.

Others are used for ‘optimisation’

The recent boom in peptide talk and use is mostly for products promoted online for more efficient weight loss, muscle growth, injury recovery, tanning, anti-ageing, libido, energy, or “optimisation” (the quest for a better you).

Most people using these products aren’t injecting into a vein. Peptides are typically injected just under the skin (subcutaneously) using smaller insulin-style needles into the abdomen, thigh or upper arm.

Others are available as nasal sprays, tablets or creams. But injection is the most common route for the enhancement peptides promoted online.

This peptide surge is just one aspect in a much broader push toward human “enhancement”, where the line between treating illness and enhancing a healthy body keeps blurring. Social media is being used to normalise enhancement substances, including peptides, well beyond elite sport.

However, because there is no routine surveillance of peptide use in Australia, we don’t yet know which peptides are most commonly used or how patterns of use are changing over time.

How are peptides regulated?

In Australia, peptide products used for therapeutic purposes are regulated as therapeutic goods.

Many of the products now being advertised or sold online are not approved by the Therapeutic Goods Administration (TGA), meaning they haven’t been assessed for safety, quality or effectiveness. This includes BPC-157 (promoted for injury and gut recovery), retatrutide (an experimental weight-loss and diabetes drug), GHK-Cu (promoted for skin and anti-ageing), TB-500 (promoted for injury recovery) and CJC-1295 (promoted for muscle growth).

Without TGA approval, importing or supplying them for human use without authorisation is against the law.

However, people are still accessing these substances, mostly via online vendors. Social media is crucial to this market and driving sales. Influencers push referral links and promote products by injecting them online and telling people how they will make their skin glow.

A key loophole suppliers use to sell these substances in the United States is labelling them as “research chemicals” or for “research use only”. But this does not mean these substances are legal or safe for human use. Nor does it apply in Australia.

What are the risks?

The biggest risk isn’t always the peptide itself. Enhancement products sold online may contain much more – or much less – of the advertised ingredient than the label claims.

Our recent laboratory testing of retatrutide found doses almost double the labelled amount.

Other products may contain impurities, contaminants or entirely different substances.

Even a correctly labelled, uncontaminated product carries risk. Most enhancement peptides have little or no human trial data, so their effects and safety in otherwise healthy people are largely unknown.

Injecting itself introduces risks of infection, abscesses and scarring, as well as blood-borne viruses if equipment is shared.

Many people using enhancement drugs such as peptides also don’t disclose their use to health and drug services, meaning they may miss out on harm-reduction advice, sterile injecting equipment and accurate health information.

What needs to be done?

As peptide use continues to grow, Australia needs:

coordinated surveillance to monitor emerging products and harms

action on how these products are marketed and sold online: enforcing existing rules against advertising unapproved therapeutic goods and holding platforms accountable for referral-link selling

better education for clinicians who are increasingly encountering peptide use in their clinical practice

evidence-based information that reaches people through the same online platforms where these products are promoted

research on the wider “enhancement” ecosystem, including how people move between products, where they source information and dosing protocols, what drives uptake, and how online communities influence norms around risk.

Harm-reduction, health education and online literacy will be critical if we want to prevent avoidable injuries while the evidence continues to evolve.