Best Peptides for Muscle Growth

Like around 30% of U.S. adults, members of our team make a point of lifting weights at least 2-3 times per week.1 Strength training outcomes are incremental, so we keep an eye out for any products or therapies that can push us forward along the way. Nowadays, peptides are an increasingly popular therapy among gymgoers.

Though clinicians have been prescribing them to clients for years, therapeutic peptides have only recently entered the mainstream health discussion, leaving many curious strength trainers wondering what options they have and which treatments deserve their consideration. That’s why we’ve written this guide to the best peptides for muscle growth: to provide scientifically supported guidance to the peptide-curious. See our summary of recommendations for a rundown. Then read further to learn about the science behind our picks.

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions about staying healthy and living healthier lifestyles.

As with every guide we write, we first acclimated ourselves to the subject through the available literature. Our cumulative research hours into peptides, for muscle growth and other applications, now number in the hundreds, and it grows by the week. When you read this, our efforts will have already exceeded the thousand-hour mark.

We also benefited from relationships with medical providers who prescribe muscle growth peptides and whose jobs entail keeping pace with new findings. Through them, we gained invaluable understanding about real-world experiences from a clinical perspective.

Additionally, like all health-related content on this website, this guide was thoroughly vetted by one or more members of our Medical Review Board for accuracy and will continue to be monitored for updates by our editorial team.

We used a four-part rubric to identify the best peptides for muscle growth. With each one we evaluated, we asked ourselves:

• Is it accessible? What must you do to get it as a safe, medical-grade product?
• Is it effective? Does it do what it’s supposed to do, according to science?
• Is it safe? Are the risks within reasonable limits?
• What about its ease of use? How do you prepare and administer it?

Here’s how our recommendations turned out in each criterion.

Accessibility

Winner: Collagen peptides

Accessibility — the relative availability of a peptide in a medical-grade form — formed the foundation of our recommendations. The peptide space abounds in esoteric treatments with peculiar alphanumeric names, but most of them are research-grade materials intended only for laboratory use. The market is comparably scarce in options that are approved for human consumption, so we focused exclusively on those that you can get from an accredited compounding pharmacy or even over-the-counter.

Collagen peptides are the most accessible option because you don’t need a prescription to get a good product. Online marketplaces, brick-and-mortar stores, and direct-to-consumer websites sell reputable brands in the $10-$60 range. Our other recommendations pose higher barriers to entry, requiring a doctor’s consultation and lab tests on top of the cost of purchase to get started. Even if you went through one of the few telehealth platforms that offer muscle growth peptides, you’d still have to satisfy more criteria than you’d face with over-the-counter collagen.

We want to note that “accessibility” takes on a different connotation for those whose muscle growth regimens involve drug testing. Collagen peptides are the sole option on our list that isn’t prohibited by the World Anti-Doping Agency, so if you’re bulking up for competitive purposes, collagen is the only peptide you can take without risking disqualification.

Effectiveness

Winner: CJC-1295 with ipamorelin

CJC-1295 and ipamorelin are both synthetic peptides that mimic naturally occurring chemicals. CJC-1295 is an analog of growth hormone-releasing hormone, but it’s modified with a longer half-life for sustained growth hormone release.2 Meanwhile, ipamorelin mimics ghrelin but operates selectively so that it targets only growth hormone release, having no impact on other hormones (e.g., cortisol) that similar peptides often affect.3 4 Together, they allow your body to produce more growth hormone more often, thus facilitating muscle growth and fat loss over an extended period.5 Because of their complementary time-release characteristics, they’re commonly used together. And because of their combined effect on plasma growth hormone levels, the combination outperforms our other recommendations in terms of directly promoting muscle growth.

But our other recommendations are effective in their own rights. In later sections, you’ll see how useful BPC-157 and TB4 can be for healing after a strenuous workout, how tesamorelin can target abdominal fat to help you achieve a healthier musculature, and how collagen peptides offer a viable alternative for strength trainers on the competitive circuit.

Safety

Winner: Collagen peptides and tesamorelin

The one known side effect of collagen peptides is the rare case of anaphylaxis, which occurs only in people with an allergy — maybe 1-4% of the population.6 7 Otherwise, researchers have seen no significant adverse events even with 15g daily doses. That’s much more than you’re likely to consume with what’s ordinarily an over-the-counter product taken in moderate quantities.8

But considering that collagen peptides are most often “retail-strength” supplements, we recognize that it wouldn’t be apples-to-apples comparing them to our other recommendations, which are medical-grade treatments.

Tesamorelin, then, is our recommendation for the safest prescription muscle growth peptide. Being a prescription-only treatment already primes it for safety since the prescribing physician will subject you to biomarker testing before writing you the script. But apart from that, tesamorelin also has a lower risk profile than BPC-157 and CJC-1295, which two peptides pose a danger of immunogenicity — causing your body to mount an immune response as though they were pathogens.9

With tesamorelin, there’s no reported risk of immunogenicity. Long-term administration appears to be “generally well tolerated” among research subjects, according to a 2008 study as well as one from 2010.10 11 To be clear, tesamorelin isn’t free of adverse events, and it isn’t appropriate for everyone, but its risks are few and mild compared to many prescription treatments. We cover its side effects in its dedicated section later in the guide.

Ease of use

Winner: Collagen peptides

If you had the option, you’d probably choose not to stick yourself with a needle. That’s why we’ve distinguished collagen peptides as the easiest-to-use muscle growth peptide: they’re usually administered via tablet, capsule, or powdered drink mix, whereas our other recommendations are almost always injected.

Taken by mouth, collagen peptides are more bioavailable than most other peptides because of their small molecular size. Studies have shown that oral collagen can be absorbed at rates as high as 63%, compared to 1-2% for other oral peptides.12 13 Injectable collagen peptides are available, but surveys show a large proportion of the population would prefer a less invasive method.14

BPC-157 is another peptide that boasts good oral bioavailability, but the same can’t be said about its frequent companion, TB4.15 16 Because we recommend BPC-157 and TB4 in combination, BPC alone failed to earn our designation as the easiest-to-use peptide.

Before we enter our deeper discussions on muscle growth peptides, check out this quick reference table for a side-by-side comparison of key points:

Not all muscle growth peptides serve the same function. Some of them facilitate muscle growth, while others optimize the body’s condition for strength exercise. The difference is subtle but important: a “facilitator” helps increase lean mass more directly, whereas an “optimizer” affects peripheral areas related to the muscle-building process. In lay terms, one helps your body respond to strength training, while the other helps keep your body in a condition to train in the first place.

The facilitators we recommend — tesamorelin, ipamorelin, and CJC-1295 — are known as growth hormone secretagogues (GHS). GHS peptides mimic the action of growth hormone-releasing hormone in the brain’s hypothalamus, stimulating the secretion of growth hormone from the pituitary gland.17 Increased growth hormone circulation induces growth in almost every bodily tissue and organ, and it also regulates the metabolism of carbohydrates and fats.18 In effect, it improves your body’s ability to increase muscle mass, use stored energy, and shed fat.5

The optimizers work differently and don’t always belong to neat classifications. In our guide, the optimizers of choice are BPC-157 and TB4, each with a self-specific mechanism of action. Because we can’t summarize their mechanisms categorically, we discuss them individually in their respective sections later in this guide.

Collagen peptides, however, can be classified broadly. Collagen is an essential structural protein that occurs naturally in your body and accounts for more than 30% of its total protein.19 As an exogenous substance, it’s absorbable only when broken down into small pieces, and that’s what collagen peptides are — very small pieces of collagen.19Though more popularly used for skin health, these peptides also increase joint elasticity and preserve muscle mass, hence fortifying a foundation to support your strength-training goals.6

Routes of administration

Subcutaneous injection is the ordinary route of administration of most therapeutic peptides. So it goes for tesamorelin, ipamorelin, CJC-1295, and TB4. That’s because peptides can easily break down in your digestive tract and are often too molecularly large to permeate your intestinal wall.20 Oral alternatives may use technologies like protective capsules and permeability agents to bypass these obstacles, but injection remains the most common peptide delivery method.20

Collagen peptides are an exception. Commercially, they’re more widely available as pills or powder mixes: the broken-down, piecemeal structure produces a small molecular size that allows the peptide to pass easily through the intestinal lining and avoid complete degradation. To illustrate, a 2015 study showed that rats fed a collagen peptide absorbed more than 63% of the collagen, whereas other orally administered peptides have exhibited low bioavailability rates as low as 1-2%.12 13

BPC-157 is an exception, too — it remains stable in gastric juice for more than 24 hours, allowing it time to pass through the gastrointestinal walls15 — but it’s often used in conjunction with the not-so-orally-bioavailable TB4.

Some muscle growth peptides are broadly safe, and others are riskier.

Collagen peptides, having no significant side effects in people who aren’t allergic, are the closest to risk-free as you can get with a consumer health product.6

Tesamorelin, at least among our recommendations, is the next best thing: two studies describe it as “generally well tolerated” and its most common side effects in indicated users — injection site reactions, joint and muscle pain — are mild compared to other therapeutic peptides.10 11

Mostly ditto for ipamorelin and TB4, except they’re often combined with peptides associated with more alarming health concerns: CJC-1295 and BPC-157, respectively. The FDA warns that CJC-1295 and BPC-157 pose a risk of immunogenicity, in which the body regards the substance as a threat and mounts an immune response against it.9 The FDA also states that the safety consequences of immunogenicity are “unpredictable” and include life-threatening events such as anaphylaxis.21 Your risk for immunogenicity can depend on many variables, including genetic and disease-associated factors, so you should undergo a careful consultation and medical assessment before using CJC-1295 or BPC-157.22

Strength trainers are the most obvious user base for muscle growth peptides, but they’re by no means the only ones that can benefit. If you live with any of the following fitness-related health conditions, you too may be a candidate:

Who are they not for?

Apart from people with a specific peptide allergy and those at risk for immunogenicity, the following populations should avoid the use of muscle growth peptides:

• People who are pregnant or breastfeeding: There isn’t enough research to determine whether muscle growth peptides can affect a developing fetus or newborn. That goes for the otherwise innocuous collagen peptides, too.30 Your best course of action is to play it safe and avoid peptide therapy while pregnant or breastfeeding.
• People with cancer or an elevated cancer risk: Growth hormone secretagogues can stimulate both cell death and cellular replication, the same biological events that preface cancer.31 Therefore, you should avoid peptides like ipamorelin and tesamorelin if you’ve survived cancer or have an active cancer diagnosis.
• People who can’t tolerate injections: Since most therapeutic peptides are administered subcutaneously by injection, they’re usually no-go for anyone who fears needles.
• Competitive bodybuilders or powerlifters: Growth factors, peptide hormones, and uncategorized peptides such as BPC-157 are prohibited by the World Anti-Doping Agency. If you’re a competitive bodybuilder or powerlifter who uses any such peptide, your next drug test may result in disqualification.

Recommended for maximizing muscle growth

Together, CJC-1295 and ipamorelin mimic two naturally occurring bodily chemicals to enhance your natural growth hormone cycle.

CJC-1295 is an analog of growth hormone-releasing hormone, which causes the pituitary gland to release growth hormone.17 With higher levels of growth hormone, your body has what it needs not only to increase its muscle strength and mass but also to break down its fat cells.32 29

Ipamorelin, for its part, is an analog of ghrelin, which also stimulates growth hormone release. Importantly, ipamorelin selectively targets growth hormone without significantly affecting stress hormones such as cortisol, high levels of which can diminish your body’s ability to metabolize nutrients, regulate blood sugar, and suppress inflammation.3 4 33

The two peptides work on different schedules, so to speak. CJC-1295 is modified to produce sustained growth hormone release, whereas ipamorelin induces a more immediate release.2 As a result, your body enjoys a longer time frame in which to optimize the higher circulation of muscle-enhancing chemicals.

Specific side effects

Some users may experience flu-like symptoms, including fever, fatigue, nausea, and headache. These effects are more common as you begin your treatment and usually don’t arise later in your therapy.

Though relatively rare, CJC-1295 poses a risk of immunogenicity, a condition in which your body reacts to a protein-based drug as though it were a pathogen.9 In such an event, you’d get none of the benefits that CJC-1295 would otherwise offer and could suffer a life-threatening allergic response.21 The best way to avoid serious adverse events related to immunogenicity is to undergo a comprehensive medical assessment at the hands of a skilled provider knowledgeable in therapeutic peptides and their potential hazards.

Recommended for recovery and healing

The BPC-157 and TB4 stack accelerates tissue repair and recovery from injury. In doing so, it helps shorten your healing period after an intense workout, thereby increasing how much time you can spend hitting the weights.

BPC-157’s role in producing these outcomes is mysterious. It’s believed to promote musculoskeletal repair by upregulating growth factors, stimulating the formation of new blood vessels, or modulating nitric oxide synthesis, but no mechanism of action has been proven.34 TB4, however, has known mechanisms by which it speeds recovery from injury: inhibiting inflammation, preventing cell death, and (as suspected with BPC) promoting blood vessel formation.35

On top of the benefits for physical recovery, the ability to form new blood vessels points to promising implications for cardiovascular health. Namely, the growth of new circulatory pathways can improve blood flow in people whose existing vessels are blocked.36

Specific side effects

In some users, BPC-157 and TB4 can cause gastrointestinal discomfort, nausea, dizziness, and headaches. These effects are more common upon the initiation of therapy.

Also, like CJC-1295, BPC-157 presents a risk of immunogenicity. Again, you should undergo a comprehensive medical assessment to rule out, as much as possible, your likelihood of experiencing this potentially life-threatening complication.

Recommended for body recomposition

Tesamorelin is FDA-approved specifically for HIV-associated lipodystrophy — excess abdominal lipid accumulation as a result of antiretroviral therapy — its efficacy against which was evidenced in a 2010 clinical trial that demonstrated an 18% decrease in visceral fat in intervention subjects compared to placebo.11 Concerning muscle growth, a later study of HIV patients determined that tesamorelin was “effective in increasing skeletal muscle area and density.”28 Also, because visceral fat is associated with increased cardiovascular mortality, tesamorelin exhibits promise as a treatment for serious health conditions like heart disease and stroke.37

Although tesamorelin studies so far have understandably centered on patients with HIV, theory holds that the peptide should have the same effects on other users. As evidence, we can point not only to the fact that medical providers prescribe tesamorelin off-label to general populations for fat loss and muscle growth, but also to a 2006 study in which growth hormone replacement therapy “significantly improved body composition” in non-HIV patients with growth hormone deficiency.38

Specific side effects

Some tesamorelin users experience flu-like symptoms such as fatigue, nausea, and headache. As with the other peptides we’ve discussed so far, these effects are more common upon the initiation of therapy.

Additionally, some users have reported joint and muscle pain. The severity of pain may vary depending on the user and the specific instance.

Recommended for competitive bodybuilders or powerlifters

Collagen peptides are unique among our recommendations because:

• They aren’t prohibited by the World Anti-Doping Agency.39
• They pose no serious side effect risk in people who aren’t allergic.6
• They’re bioavailable via oral administration.12
• You don’t need a prescription to get them.

These qualities make collagen the ideal option for competitive weightlifters, as well as anyone who’d rather not see a doctor or stick themselves with a needle.

But are they effective? The studies say yes.

For example, in 2015, a randomized clinical trial of elderly men with sarcopenia found that 15g of daily collagen peptide supplementation, in combination with resistance training, led to improvements in multiple parameters: muscle strength, fat mass, and fat-free mass.40

For another example, a 2023 study of subjects with ultrasound-confirmed musculoskeletal inflammation concluded that locally injected collagen peptides could “effectively and safely treat collateral ligament pain,” indicating positive implications for physical recovery.41

It isn’t clear how collagen compares to other peptides in facilitating these outcomes, as head-to-head studies aren’t available. Also, some medical providers are more confident that injectable forms are more efficacious than oral alternatives. Still, collagen peptides in general remain a largely low-barrier therapeutic option for the largest number of potential users.

Specific side effects

As we said, collagen peptides pose no serious risk of common side effects.6 Only people who are allergic to collagen supplements — around 1-4% of the population7 — should outright avoid them. Nonetheless, you should speak with your doctor before incorporating collagen into your supplementation regimen. A comprehensive health assessment and review of your medical history can help you navigate any potential hazards and other considerations.