Lifting the curtain on the peptide craze (April 2026)

By Carrie Dennett, MPH, RDN

Peptides are a hot topic in the wellness/anti-aging space, especially among biohackers and others who want to increase longevity and prevent chronic disease. The claims—many coming from celebrities and wellness influencers—are that peptides are something of a magic elixir, a fast track to improving cognition, memory, muscle strength, sexual function, and/or sleep, as well as reducing aging, producing younger-looking skin, repairing cells, reducing inflammation, and so on.

Let’s take a look at what peptides are exactly, and what the evidence tells us about their potential benefits and potential harms. In simple terms, peptides are short strings of amino acids, the building blocks of proteins. So, basically, peptides are short proteins. Our bodies make many peptides—insulin is one notable example—that play a role in regulating hormones, repairing tissue and releasing neurotransmitters.

Companies have been adding laboratory-made peptides to skin care products for decades, but the recent flush of peptide popularity is mostly about injectable peptides. Some of these peptides are synthetic versions of peptides our bodies make, others are completely foreign to the human body.

The Food and Drug Administration (FDA) has approved a number of peptides for very specific diseases or other health concerns. For example, for HIV-related conditions, diabetes, chronic hepatitis B, cancer, bone disorders, irritable bowel syndrome. All of these have been tested for safety and effectiveness in human randomized clinical trials. However, some of these peptides are being used “off label” for uses they haven’t been studied for, such as increasing muscle mass, boosting immunity, and for “anti-aging.”

Beyond that, there’s a whole slew of peptides touted as quick fixes for all the claims already mentioned, and more. Trouble is, none of these claims have real evidence* to back them up, because they have not been tested by randomized controlled clinical trials in humans. At best, they’ve been tested in rodents and Petri dishes.

* On that note, be cautious about anyone saying, “I’ve been taking Peptide X and it’s done this, that and the other for me!” the placebo effect (when you see a certain result just because you expect to) is real.

This means that most of the unproven peptides promoted online are technically being sold illegally, because any substance that purports to produce a health benefit or prevent a medical condition is classified as a drug, which cannot be sold without FDA approval. Many peptides are classified as biologics, the most complicated and potentially high-risk type of drugs, requiring extra precautions in their manufacture and storage. In recent years, the FDA has added more than two dozen peptides to a list of substances that should not be produced by pharmacies due to safety risks.

Right now, anyone can stick out a shingle selling peptide injections, and there’s no way to know what you’re really getting. (It’s worth noting a large proportion of peptides come from China.) Even if a peptide is simply a synthetic form of a naturally occurring peptide, it doesn’t mean injecting it will provide extra benefits. Because peptides are unstable, they break down when they’re put in a skin cream, and peptides in supplement are degraded by digestion before they ever enter the bloodstream.

While it would certainly be disappointing to shell out hundreds of dollars, or more, for peptide injections and have them not produce tangible results, they also have serious potential side effects. Injection site swelling and redness is one, but synthetic peptides may have extra ingredients to help them absorb better or prevent them from degrading, and those ingredients have the potential to produce an allergic or other adverse reaction. Two women almost died last year after receiving peptide injections at a Las Vegas anti-aging festival. Other concerning affects include:

• One peptide that has anti-inflammatory claims attached to it was found, in animals (because, again, there’s no human studies), to accelerate the growth of dormant tumors and disrupt the immune system.
• A few peptides (including one that’s FDA-approved) can increase the risk of cancer.
• Certain peptides that supposedly increase muscle growth can also reduce your body’s sensitivity to insulin, increasing blood sugar.
• Similarly, peptides that mimic hormones can push normal hormones out of balance, affecting sleep, metabolism, menstrual cycles and more.

Assuming a peptide is actually safe and effective, because there’s a lack of research on humans, we don’t have information on the right dose or the impact of long-term use. The bottom line is that the peptide fad is without merit. The emperor has no clothes.

Links:

Damon A. A Las Vegas Festival Promised Ways to Cheat Death. Two Attendees Left Fighting for Their Lives. ProPublica, July 29, 2025. https://www.propublica.org/article/peptide-injections-raadfest-rfk-jr

Achilleos K, Petrou C, Nicolaidou V, Sarigiannis Y. Beyond Efficacy: Ensuring Safety in Peptide Therapeutics through Immunogenicity Assessment. J Pept Sci. 2025 Jun;31(6):e70016. https://pmc.ncbi.nlm.nih.gov/articles/PMC12010466/

Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Updated July 8, 2025. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks