A report from RTE examines the boom in self-administered peptide injections promoted on social media, where users advertise faster muscle growth, weight loss and better skin, and asks what is actually known about the risks.

Peptides are chains of amino acids that occur naturally in the body. Christian Seifarth, founder and managing director of the Bavarian Centre for Endocrinology and Metabolism, describes them as proteins with signalling properties that trigger specific processes, acting as hormones, neurotransmitters or growth factors that regulate bodily functions and promote cell growth and tissue repair.

Why the mechanism cuts both ways

Seifarth says peptides are not dangerous in themselves, since the body produces many of these signalling molecules on its own. That is not an argument for synthetic versions being harmless, and he is blunt about why: the danger lies in the effect, because these substances act specifically on organs and structures, and there is always a downside.

He draws a line between a molecule the body makes in a particular place and the same molecule injected into an abdomen or an upper arm. Those are not the same event, and the report treats that distinction as the core of the safety question rather than a footnote.

Who is watching the trend

Tami, 31, injects peptides and has spent a year collecting data on different preparations, posting about her experiences and the potential risks. Within the TikTok bubble, she says, a lot of it sounds like established science, but a closer look at the studies shows many findings come from animal experiments or cell cultures.

She receives messages from users aged 13 to 17, some reporting fever, redness or bruising after use and asking for advice. Her answer is the right one: anyone who develops a fever should see a doctor, not post on a forum. Seifarth flags the same age group specifically, warning that growth could be affected and puberty disrupted.

Marketing in a lab coat

Tami's phrase for the sales pitch, in the absence of meaningful human trials, is marketing in a lab coat. Seifarth adds a physical risk that the content rarely mentions: preparations could be contaminated with bacteria, and injecting them could mean an infection.

He is dismissive of the anti-aging logic in particular, comparing it to hormone preparations of the 1990s and calling the approaches highly questionable.

Bottom line

Seifarth calls peptides very interesting biochemically and says they do have potential. His conclusion is that it is far too early to use them in people, because too little is known to do so responsibly.