Key takeaways:
Peptides are getting a lot of attention for their potential to build muscle and improve strength. But there’s little human research that supports this claim.
Some peptides increase levels of hormones that are involved in muscle growth. But increased hormone levels don’t always mean more muscle.
Peptides marketed for muscle growth aren’t FDA approved. And researchers have concerns about their short- and long-term safety.
There’s a lot of discussion around peptides these days: as a way to build muscle, recover faster after workouts, and lose fat. All of these potential benefits sound appealing. But the excitement is outpacing the research.
Certain peptides affect hormones that play a role in muscle growth. But building muscle isn’t as simple as changing a hormone level. And we have little research to know if these peptides are beneficial — or even safe.
Here, we’ll cut through the noise and explain what peptides are, the research around them for muscle growth, and safety concerns.
What are peptides?
Peptides are small chains of amino acids. Amino acids are the building blocks of proteins that make up muscle, skin, and other tissues. Your body naturally makes peptides that help regulate hormones, metabolism, and your immune system.
Some peptides are made in labs and developed into FDA-approved medicines — like insulin. Another example is glucagon-like peptide-1 (GLP-1) medications, which are based on a peptide involved in blood sugar regulation and appetite.
But the peptides that people are talking about for muscle growth aren’t approved medications. They’re mostly experimental substances.
How do peptides work for muscle growth?
A lot of the excitement around muscle-building peptides comes down to one hormone: growth hormone (GH).
Your body naturally makes GH to help with growth and metabolism. GH causes your body to make another hormone called insulin-like growth factor 1 (IGF-1). Both GH and IGF-1 help your body build and maintain muscle.
Some experimental peptides known as GH secretagogues (GHS) cause your body to make and release more GH. This, in turn, boosts your IGF-1 levels. But there are no studies evaluating if higher GH or IGF-1 levels actually lead to muscle growth.
Which peptides have been studied for muscle growth?
Very few peptides have been actually studied for muscle growth in humans. The peptides that are getting attention for muscle growth include:
GH-releasing hormones (GHRHs) like CJC-1295, CJC-1293, sermorelin, and tesamorelin. A human study found that CJC-1295 increased GH and IGF-1 levels. But the study didn’t measure muscle growth.
GH-releasing peptides (GHRPs) like hexarelin, alexamorelin, GHRP-2, GHRP-3, GHRP-4, GHRP-5, and GHRP-6. There’s no research on their effects on muscle growth in humans.
Ghrelin (also called lenomorelin) and peptides that mimic it, such as ipamorelin and tabimorelin. Ghrelin is a hormone that regulates hunger and can stimulate GH release. But like GHRPs, there are no studies directly evaluating their effect on muscle growth.
So, the big picture is this: We know some of these peptides can change GH levels. We don’t know if they help healthy people build bigger or stronger muscles. For all of them, that research simply hasn’t been done.
Are peptides safe?
Peptides that are FDA approved for specific medical conditions — like insulin for diabetes or GLP-1 medications for weight loss — are safe.
However, it’s unclear if experimental peptides are safe. They haven’t been studied in large human trials. So we don’t know about their side effects, especially if they’re used multiple times over long periods.
The FDA has raised concerns about several peptides, including ipamorelin, CJC-1295, and GHRP-6. Potential risks include:
Contamination: Peptides sold online aren’t regulated, and they may contain harmful ingredients.
Infection: Injecting peptides can introduce bacteria into your body — both from contaminated supply or the injection itself. This may lead to a serious life-threatening infection.
Heart problems: Increased heart rate and drops in blood pressure have been reported in people taking CJC-1295.
Are there safe alternatives to peptides for muscle growth?
Yes, there are safe alternatives to peptides. And the good news is that the safest ways to build muscle are also the most effective, according to research. Here are some examples:
Regular resistance training, like lifting weights, helps your muscles grow stronger over time.
Getting enough protein is also important, because your body needs amino acids to build and repair muscle.
Some supplements have solid research behind them. Creatine in recommended doses can increase strength and muscle growth. This effect is especially noticeable when paired with resistance training.
Sleep and recovery are key as well. Your muscles need time to repair and grow between workouts.
Are peptides safer than steroids?
We don’t know if peptides are safer than steroids. There’s not enough research comparing peptides to steroids.
Anabolic steroids are lab-made versions of testosterone, another hormone involved in muscle growth. At high doses, anabolic steroids can be dangerous. Risks include liver damage, heart attack, and stroke.
So, while peptides are sometimes promoted as a safer alternative to steroids, there isn’t enough data to support that claim. It’s best to assume that neither is a safe way to build muscle.
The bottom line
Some experimental peptides can increase hormones involved in muscle growth. But we don’t know whether those changes help healthy people build more muscle or get stronger. And there are still many unanswered questions about their short- and long-term safety. For now, the best ways to build muscle are regular strength training, meeting your protein needs, and proper recovery. These ways may not sound as exciting as the latest peptide trend, but they have much more research proving they’re safe and effective.
Why trust our experts?
References
Nass, R., et al. (2011). The role of ghrelin in GH secretion and GH disorders. Molecular and Cellular Endocrinology.
National Institute on Drug Abuse. (2023). Anabolic steroids and other appearance and performance enhancing drugs (APEDs).
Olarescu, N. C., et al. (2025). Normal physiology of growth hormone in normal adults. Endotext
Sigalos, J. T., et al. (2018). The safety and efficacy of growth hormone secretagogues. Sexual Medicine Reviews.
Teichman, et al. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. The Journal of Clinical Endocrinology and Metabolism.
U.S. Drug Enforcement Administration. (2024). Steroids.
U.S. Food and Drug Administration. (2026). Certain bulk drug substances for use in compounding that may present significant safety risks.
