Beginner’s Guide to Peptide Therapy

In recent years, the peptide space has seen a significant uptick in drug discovery, clinical research, and therapeutic applications.25 Even so, these treatments remain unfamiliar to a lot of prospective patients, who aren’t exactly sure what peptides are or how they work.

It’s not their fault. Peptides are a complex subject with strange drug names, shared and sometimes contradictory potential effects, and confusing regulatory statuses. That’s why we’ve written this guide and structured it as we have. Where applicable, as we discuss each aspect of different peptide therapies, we start with a high-altitude view and then zoom in on the caveats and exceptions that make them unique. That way, you get both a broad sense of how peptides can work and a specific sense of which ones might work for you.

In the end, we trust you’ll have all the information you need to make the best-informed decision about your own peptide therapy, should you pursue it.

But if you’ve already decided that peptides are the thing for you, you’ll want to know how to get some. Finding a good source of peptides is no easy task right now because so much of what you find online are research-grade peptides not intended for anything but lab research. We’ve done the legwork and vetting to find a recommendable telemed provider called Bridgeside Telehealth.

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.

Our team has been exploring the peptide space for years. For every hour we’ve put into writing about peptides, we’ve devoted two or three hours to research. All told, our total clock time on the subject exceeds 1,000 hours. Along the way, we’ve gained invaluable insights from medical providers who prescribe peptides, as well as from people who use them.

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.

Peptides occur naturally in the body (endogenous) but can also be administered externally (exogenous).

The basics that underlie all peptides, endogenous and exogenous alike, are these:

• Peptides are strings of amino acids.
• Amino acids are molecules that combine to form protein molecules.
• Proteins are essential for a diverse array of bodily functions, including but not limited to immune function, muscle contraction, metabolism, physical growth, physical structure, blood oxygenation, and sexual arousal.1

The human body needs an adequate supply of 20 amino acids to function properly,2 but those 20 amino acids can combine in thousands of unique sequences to form different peptides with distinct biological functions. By supplementing your endogenous supply of peptides with exogenous sources, you provide your body with more of the resources it needs to carry out specific functions.

Therapeutic peptides

Those exogenous sources, when used to treat health conditions, are called therapeutic peptides. Given the varied roles that peptides assume in the human body, you can imagine that therapeutic peptides have a vast array of potential applications in human health. By way of example, consider this table of common therapeutic peptides and their primary health outcomes:

In many cases, therapeutic peptide prescriptions are given off-label (i.e., to treat health conditions other than what a peptide is approved for).

Take tesamorelin, for example. As an analog of endogenous growth hormone-releasing hormone (GHRH), tesamorelin boasts a metabolism-stimulating activity that has led to its being approved as a treatment for lipodystrophy, or abnormal adipose fat accumulation associated with antiretroviral therapy for HIV.3 But this same activity can help non-HIV individuals shed abdominal fat of their own, while the peptide’s GHRH properties make it a suitable therapy for people looking to increase their lean mass. Therefore, it isn’t uncommon to see tesamorelin given as an off-label prescription for weight loss or muscle growth.

Routes of administration

With regard to routes of administration, therapeutic peptides are often injectables, administered subcutaneously by needle. That’s because peptides degrade easily in the digestive tract and tend to be too large molecularly to permeate the skin or intestinal lining,5 often yielding a bioavailability as low as 1-2%.6

But there are some peptides that have a small enough molecular size that they easily transfer into the bloodstream as either an oral or a topical supplement. A couple of good examples are collagen, with an oral bioavailability as high as 63%,7 and GHK-Cu (copper peptides), which can pass through the skin in therapeutically effective amounts, per a 2010 study.8

Preparation and storage of injectable peptides

An injectable peptide normally comes in powder form. Before you can use it, you must reconstitute it into a solution. Likely, your peptide prescription will also come with everything you need to do just that — bacteriostatic water and needle syringes.

Generally, the reconstitution process entails drawing a measure of bacteriostatic water into a syringe and then introducing that water to the peptide powder. Your prescriber’s instructions should specify how much water to use and how to dissolve the powder. However much water you’re supposed to use, avoid shaking the solution, as it can degrade the peptide.

A shipment of peptide powder, once reconstituted, should last a month when stored appropriately. The ideal storage temperature is around 4°C, or 39°F,9 so a refrigerator is the best place for it.

While peptides can potentially serve myriad health goals, we can broadly organize the most commonly sought-after peptides into five categories based on their primary benefits. In the following sections, we discuss those categories and the peptides most often associated with them.

Weight loss peptides (GLP-1 RAs)

Originally developed as diabetes treatments, glucagon-like peptide 1 receptor agonists (GLP-1 RAs) exhibit mechanisms of action on metabolism and the pancreas that promote weight loss by:26

• Slowing digestion: A longer time to gastric emptying correlates not only with a decreased appetite but also with a milder glucose spike.27 28 A decreased appetite means less desire to consume excess calories, and a less severe spike indicates tighter regulation over a significant weight-gain factor.29
• Increasing feelings of fullness: When you do get hungry, a GLP-1 RA can help you reach satiety sooner than you normally would. Ideally, that leads to eating less food during mealtimes and, therefore, consuming fewer calories throughout the day.

Today, the most popular and widely used peptides for weight loss are tirzepatide and semaglutide, which you may know by the respective brand names Mounjaro and Ozempic. Both have a wealth of scientific support for their efficacy, but tirzepatide has a bit more evidence behind it. In a 2021 study, for example, subjects who received tirzepatide lost around 4-12 more pounds than their semaglutide counterparts.30 But semaglutide is still a terrific option for fast weight loss, and it’s more easily accessible through reputable telehealth platforms.

Body recomposition

Body recomposition refers to the process of gaining muscle and shedding fat. In our categorization, it’s this muscle growth factor that separates body recomposition peptides from GLP-1 RAs.

Many body recomposition peptides are growth hormone secretagogues, or substances that stimulate the body’s production of growth hormone, which itself promotes physical growth and helps regulate body fat composition through a different hormone called insulin-like growth factor-1.31 32 Some of the more commonly used growth hormone secretagogue peptides are CJC-1295, ipamorelin, sermorelin, and tesamorelin. (Tesamorelin is also prescribed to treat HIV-associated lipodystrophy, or excess abdominal fat accumulation resulting from antiretroviral therapy. That is, in fact, the application for which it’s FDA-approved.)

Besides growth hormone secretagogues, there are several uncategorized peptides that many people use to increase their muscle mass. Examples of these include BPC-157 and TB4/TB500, which are often used together for their synergistic potential to stimulate muscle gain while speeding up recovery.

General wellness

Peptides for general wellness constitute the broadest category, as wellness refers to several target health outcomes: longevity, immune health, and quality of life (the last of these itself being a pretty broad designation). Examples of such peptides include:

• MOTS-c: MOTS-c is a naturally occurring protein hormone that may improve metabolic function,33 reduce inflammation,34 and improve bone health,35 among other things.
• Epitalon: Consisting of four amino acids, epitalon can help preserve the lengths of telomeres (the caps on the ends of chromosomes) and regulate melatonin. In doing so, it may stave off age-related diseases associated with telomere shortening,36 strengthen the immune system,37 and improve sleep health.38
• Delta sleep-inducing peptide (DSIP): As its name suggests, DSIP helps with sleep. It may also attenuate stress and have applications as an anticonvulsant, antidepressant, and neuroprotective agent.39
• Thymosin alpha-1: Thymosin alpha-1 may offer numerous benefits related to immune function, including but not limited to treating hepatitis B, treating infections, improving vaccine efficacy, and reducing the toxicity of chemotherapy.40
• GHK-Cu: GHK-Cu is a complex of copper and the peptide GHK. It has quality-of-life applications related to skin health, as research supports its ability to tighten loose skin, improve skin firmness, reduce photodamage, promote wound healing, and more.41
• Insulin: Insulin is a quality-of-life treatment for managing blood sugar. It’s helpful for people with type 2 diabetes and necessary for those with type 1 diabetes.42

Cognitive enhancement

Cognitive enhancement peptides are similar to nootropics in that they can improve focus, memory, and mental clarity, as well as associated factors like anxiety and mood. Two promising synthetic peptides in this category are Selank and Semax. Studies on the former have shown that it can produce a stable and sustained influence on learning and memory,43 while the latter may be able to support the differentiation, maturation, and survival of neurons in the brain.44

Another potential cognitive enhancement peptide is Pinealon, which can improve learning and memory by modulating gene expression and neurotransmitter activity. In rodents at least, Pinealon administration has correlated with an improved ability to negotiate a maze,45 suggesting that the subjects could acquire and retain information more effectively.

Sexual function

Peptides for sexual function are either alternatives or adjuncts to more ordinary prescription treatments such as sildenafil and tadalafil. One such peptide, called PT-141 (a.k.a. bremelanotide), has been described as a “promising way to treat [hypoactive sexual desire disorder],”46 a condition characterized by a chronic lack of sexual desire.47 PT-141 is available as a women-only prescription under the brand name Vyleesi, clinical trials for which have shown the drug to both improve sexual desire and decrease feelings of associated distress.48

PT-141 has also been tested in men, as in a 2005 study that coadministered the peptide with sildenafil to subjects with ED who either had not responded to or could not tolerate single-therapy treatment. Among this cohort, coadministration was deemed to be a “viable therapy.”49

Another possible sexual peptide solution, for both men and women, is oxytocin, which may have some role in stimulating sexual attraction.50 But more research is needed, as some studies have found oxytocin to be ineffective at improving sexual behavior.51

Besides their specific use applications, we can broadly classify therapeutic peptides into three categories based on how they’re produced for the market:

• Bioactive peptides
• Synthetic peptides
• Recombinant peptides

Their differences lie not in their respective efficacy but in their feasibility and cost-effectiveness. That is, from a production perspective, some peptide varieties lend themselves more to one production method than either of the other two.

Bioactive peptides

Bioactive substances are found in organic matter, such as plants, animals, and animal products, so bioactive peptides might also be categorized as natural peptides.10

Bioactive peptides can be consumed via dietary sources, including but not limited to eggs, soy, legumes, meat (including seafood), and dairy.11 Or else they can be isolated, extracted, and processed into oral or even topical supplements. Two common production techniques for bioactive peptides are enzymatic hydrolysis and microbial fermentation, which are both ways to break proteins down into smaller peptides or individual amino acids.12

The realm of bioactive peptides is somewhat limited because, remember, peptides can easily break down in the digestive tract, and many are too molecularly large to permeate the skin or intestinal lining.5 But there are several peptide varieties that are readily bioavailable by oral or transcutaneous administration, such as collagen and GHK-Cu.

Synthetic peptides

Synthetic peptides are lab-derived, created by deliberately linking amino acids in sequences that mimic endogenous peptides. It’s by this method that you get some of the best-known pharmaceutical peptides, like semaglutide, tirzepatide, and tesamorelin.

If endogenous peptides are like OEM parts in the machinery of your body, then we can liken synthetic peptides to 3D prints: in terms of structure and function, they’re similar if not identical.

The drawback of synthetic peptides is that they’re largely limited to short chains of up to 50 amino acids, as longer peptides present a greater challenge from a large-scale-manufacturing perspective.13

Recombinant peptides

Recombinant peptides are those produced via recombinant DNA technology, by which scientists manipulate and isolate DNA segments to express the genes of specific peptides.14 Think of it as the Venn common ground between the bioactive and the synthetic, a biotechnological hybrid relying on both organic and laboratory processes. With recombinant technology, therapeutic peptide chains can more easily exceed 50 amino acids. Producing such peptides can be costlier up front, but may be more efficient on larger scales.

In theory, pharmaceutical-grade therapeutic peptides are generally safe because peptides already occur in the human body. That includes synthetic peptides, which mimic their naturally occurring counterparts in form and function. For example, a normally functioning body already produces collagen and GHRH, so adding collagen peptides or a GHRH analog should only enhance naturally occurring biological processes. For most nonpregnant, non-breastfeeding people without specific allergies, adverse events are limited to mild and transient flu-like effects and (for injectables) injection site reactions.

But in practice, and especially with regard to synthetic and recombinant peptide forms, there are some considerable potential safety concerns:

These are only the prominent issues associated with some of the better-known therapeutic peptides. When you more thoroughly explore the peptide pantheon, you’ll find that more obscure peptide treatments have been known to cause other life-threatening issues such as:19

• Heart toxicity (by cesium chloride)
• Arrhythmias (by cesium chloride and domperidone)
• Kidney injury (by germanium sesquioxide)

Peptide legality is a complex issue. Some therapeutic peptides (e.g., collagen) are readily available over the counter. Some need a doctor’s prescription but are otherwise widely available (e.g., GLP-1 RAs like semaglutide and tirzepatide). But then there are others that, in the United States, currently drift in a state of legal limbo.

The complexities arise from Section 503A of the Federal Food, Drug, and Cosmetic Act, which relates to the necessary conditions for drug compounding.20 The rules concerning the compounding of therapeutic peptides state that they must come from accredited compounding pharmacies, and the compounded drug must either be compounded from an existing FDA-approved drug product or use drug products included on the 503A bulks list (i.e., the FDA’s roster of compoundable substances.)21

But many therapeutic peptides don’t satisfy either of the 503A conditions. That includes several that we’ve highlighted in this guide:22

• BPC-157
• CJC-1295
• Epitalon
• GHK-Cu (as an injectable)
• Ipamorelin
• MOTS-c
• Selank
• Semax
• Thymosin alpha-1
• Thymosin beta-4

That doesn’t mean that you can’t get a prescription for these peptides; in fact, in the interim while they undergo evaluation for bulks list inclusion, the FDA will not enforce prohibition against them. Plus, Section 503A allows for exemptions. With a valid prescription indicating that a compounded treatment is “necessary for the identified patient,” any of the above peptides could be made available.23 Just know that necessary is an operative word there. A doctor may prescribe you a peptide, but they might also need to document why you can’t use other, less legally restricted treatment options.

Several well-known telemed providers sell pharmaceutical-grade peptides, but most catalogs are limited to GLP-1 RAs such as semaglutide and tirzepatide, plus maybe a handful of others for muscle growth.

Lesser-known peptides are also available online, but often they’re research-grade products not intended for human consumption. You can get research-grade peptides without a prescription, but unless you mean to conduct your own in vitro experiments, you should leave them alone. That’s because research-grade peptides aren’t subject to the same quality controls as their pharmaceutical-grade counterparts, and many have purity levels as low as 60%.4 Thus, they have a greater potential to be toxic and cause the life-threatening adverse effects we discuss under “Therapeutic peptide safety.”

But there’s one provider we’ve vetted whose catalog includes nearly all of the peptides named in this guide, and that’s Bridgeside Telehealth. Apart from its catalog, what distinguishes Bridgeside in the peptide telemed landscape is its attention to patient suitability and safety. Its intake process involves not only a live physician consultation, but also ongoing care support for the duration of one’s treatment. If you’ve decided to pursue peptide therapy at this time, we haven’t found a better place to do it. Bridgeside is available in most U.S. states, and its service area is expanding. You can schedule your Bridgeside consultation here.

The 503A bulks list is a living document, continuously in flux. The restricted peptides we’ve named may one day find their way onto the list, thereafter becoming more widely available to prescribed patients. Meanwhile, new potential peptide drugs are being discovered,24 suggesting promising but as-yet-undetermined directions in the treatment of common health concerns. So, as developments and trends emerge, we’ll update this guide accordingly, keeping you current on the information you need to direct your own peptide therapy.