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Types of Peptides: Complete Classification Guide

All types of peptides classified by function, administration method, and regulatory status. Find the right peptide category for your goals.

By Pure Peptide Clinic Editorial Team · Reviewed by Dr. Javed Iqbal, MBBS · Updated 2026-03-11

There are over 80 peptides in active clinical use today, and they do wildly different things. Some help you lose weight. Others heal injured tendons. Some boost growth hormone. A few protect your brain. Without a way to organize them, the whole field feels like an overwhelming alphabet soup of abbreviations.

This guide classifies every major therapeutic peptide three ways: by what it does (function), how you take it (administration route), and whether it’s legal to obtain (regulatory status). If you’re new to the concept, start with what are peptides for the basics, then come back here for the full map. For a broader introduction to therapeutic use, our peptide therapy guide covers the fundamentals.

Key Takeaways

  • Peptides fall into 7 functional categories: growth hormone, weight loss, healing/recovery, anti-aging/cosmetic, cognitive, immune/metabolic, and sexual health
  • Administration varies: injectable (most common), oral, nasal, and topical — each with different bioavailability tradeoffs
  • Regulatory status is complicated: only a handful are FDA-approved; most are prescribed off-label through compounding pharmacies
  • Many peptides cross categories — BPC-157 helps with healing, gut health, and inflammation simultaneously

Table of Contents

Classification by Function

Function is the most useful way to think about peptides. When someone walks into a peptide therapy clinic and says “I want to recover faster” or “I want to lose weight,” the answer starts with the right functional category.

Growth Hormone Peptides

The largest category in clinical practice. These peptides stimulate your pituitary gland to produce more growth hormone (GH), which affects everything from body composition to sleep quality to skin health.

GHRH Analogs (mimic the body’s natural GH-releasing hormone):

  • Sermorelin — the original, FDA-approved (brand discontinued). 29-amino-acid GHRH analog with the longest clinical track record
  • CJC-1295 — synthetic GHRH analog available with or without DAC (Drug Affinity Complex). Most commonly paired with ipamorelin. See CJC-1295 + Ipamorelin
  • Tesamorelin — FDA-approved (Egrifta) for HIV lipodystrophy. Reduces visceral fat by 15-20% in clinical trials [1]. Compare it to GLP-1 drugs in our tesamorelin vs. semaglutide guide

GH Secretagogues (activate the ghrelin/GHS receptor):

  • Ipamorelin — the cleanest secretagogue, minimal cortisol/prolactin effects [2]. See ipamorelin benefits
  • GHRP-2 — stronger GH release than ipamorelin but with more hormonal side effects
  • GHRP-6 — potent but causes significant hunger via ghrelin activation
  • Hexarelin — strongest acute GH release but develops tolerance quickly
  • MK-677 (Ibutamoren) — the only oral option, technically a non-peptide GH secretagogue with ~24-hour half-life [3]

For a deep comparison of all eight, see our growth hormone peptides guide. GH peptides are the backbone of protocols for muscle growth, sleep improvement, energy, and anti-aging.

Weight Loss Peptides

This category has exploded since the GLP-1 revolution. These peptides affect appetite, metabolism, and fat storage through different mechanisms.

GLP-1 Receptor Agonists:

Fat-Targeting Peptides:

  • AOD-9604 — a fragment of human growth hormone (amino acids 177-191) that stimulates lipolysis without affecting blood sugar or growth [5]. See our AOD-9604 guide
  • Tesamorelin — while primarily a GH peptide, its FDA-approved use is specifically for visceral fat reduction

Metabolic Peptides:

  • MOTS-c — mitochondria-derived peptide that improves insulin sensitivity and metabolic function [6]. Full guide: MOTS-c peptide
  • 5-amino-1MQ — inhibits NNMT enzyme, shifting metabolism toward fat burning

For protocol details, see our peptides for weight loss pillar guide, plus focused pages on peptides for fat loss, peptides for belly fat, and peptides for metabolism. Wondering how peptides compare to standalone GLP-1 drugs? See peptides vs. semaglutide.

Healing and Recovery Peptides

These peptides accelerate tissue repair — tendons, ligaments, muscles, gut lining, and more. They’re popular with athletes and anyone recovering from injury or surgery.

Tissue Repair:

  • BPC-157 — Body Protection Compound. A 15-amino-acid fragment of a gastric protein. Accelerates healing of tendons, ligaments, muscle, and gut tissue in animal studies [7]. The most versatile healing peptide available. See also: BPC-157 dosing, BPC-157 for arthritis, BPC-157 for gut health
  • TB-500 (Thymosin Beta-4) — promotes angiogenesis (new blood vessel formation) and cell migration to injury sites. Works through different mechanisms than BPC-157, which is why they’re often stacked together
  • The Wolverine Stack — BPC-157 + TB-500 combined for maximum recovery. Named for the comic book character’s rapid healing

Joint and Bone:

  • BPC-157 and TB-500 are the primary options for joint pain and bone healing
  • GH peptides indirectly support joint health through increased collagen synthesis

Gut Healing:

For an overview of recovery-focused protocols: best peptides for recovery.

Anti-Aging and Cosmetic Peptides

These peptides target visible signs of aging — skin quality, hair loss, and cellular repair mechanisms.

Skin and Collagen:

  • GHK-Cu (Copper Peptide) — a naturally occurring tripeptide that declines with age. Stimulates collagen production, reduces wrinkles, and promotes wound healing [8]. Available as injectable, topical, and serum formulations. See GHK-Cu for hair
  • Matrixyl (Palmitoyl Pentapeptide-4) — topical peptide in many skincare products that stimulates collagen I and III production
  • Argireline (Acetyl Hexapeptide-3) — topical peptide that relaxes facial muscles, sometimes called “Botox in a bottle” (it’s not, but it does have mild effect)

Hair Growth:

  • GHK-Cu is the primary peptide for hair growth, with studies showing it increases follicle size and extends the growth phase
  • GH peptides also support hair through increased IGF-1

Cellular Anti-Aging:

  • Epitalon — a tetrapeptide that may activate telomerase, the enzyme that maintains chromosome end-caps (telomeres). Animal studies show lifespan extension, but human data is limited [9]
  • NAD+ precursors — while not peptides in the strict sense, NAD+ therapy is often grouped with peptide protocols. See NAD+ benefits and NAD+ side effects

Full coverage: peptides for skin and peptides anti-aging.

Cognitive and Neuroprotective Peptides

A smaller but growing category. These peptides affect brain function, memory, and neuroprotection.

  • Semax — a synthetic analog of ACTH(4-10) developed in Russia. Enhances BDNF expression (brain-derived neurotrophic factor) and shows nootropic effects in clinical studies. Administered as a nasal spray [10]
  • Selank — an analog of the naturally occurring peptide tuftsin. Anxiolytic and nootropic properties. Also nasal administration
  • Dihexa — an angiotensin IV analog that crosses the blood-brain barrier. Shown to be 10 million times more potent than BDNF at promoting neural connections in animal models, though human data is virtually absent
  • BPC-157 — emerging research suggests neuroprotective effects alongside its healing properties

For more: peptides for cognitive function.

Immune and Metabolic Peptides

Peptides that modulate immune function or target specific metabolic pathways.

  • Thymosin Alpha 1 — a 28-amino-acid peptide naturally produced by the thymus. FDA-approved in over 30 countries (not the US) for hepatitis B and as an immune adjuvant. Enhances T-cell function and NK cell activity [11]
  • LL-37 — an antimicrobial peptide that’s part of the innate immune system. Being studied for infection resistance and wound healing
  • MOTS-c — mitochondrial-derived peptide that improves insulin sensitivity, exercise capacity, and metabolic health [6]
  • BPC-157 — modulates inflammatory pathways, particularly in the GI tract

Sexual Health Peptides

  • PT-141 (Bremelanotide) — FDA-approved (Vyleesi) for hypoactive sexual desire disorder in premenopausal women. Works on melanocortin receptors in the brain rather than blood vessels — fundamentally different from Viagra/Cialis [12]. See PT-141 for women and PT-141 side effects
  • Kisspeptin — stimulates GnRH release, being studied for both sexual arousal and reproductive endocrinology

Classification by Administration Route

How you take a peptide affects its bioavailability, convenience, and cost. Here’s the breakdown:

Injectable Peptides (Subcutaneous)

The most common route for therapeutic peptides. Subcutaneous injection into belly fat or thigh provides reliable absorption with 90-100% bioavailability.

Most injectable peptides: BPC-157, TB-500, CJC-1295, Ipamorelin, Sermorelin, GHRP-2, GHRP-6, Hexarelin, Tesamorelin, GHK-Cu, Thymosin Alpha 1, PT-141, AOD-9604.

Requires reconstituting lyophilized powder with bacteriostatic water, then drawing doses with an insulin syringe. See our how to inject peptides guide, peptide injection sites, where to inject BPC-157, and best time to inject peptides.

Supplies needed: bacteriostatic water, insulin syringes, alcohol swabs. Full mixing tutorial: how to mix peptides.

Oral Peptides

Most peptides are destroyed by stomach acid and digestive enzymes, making oral delivery challenging. The exceptions:

  • MK-677 (Ibutamoren) — not technically a peptide, which is why it survives digestion
  • Semaglutide — available in oral form (Rybelsus) using a special absorption enhancer (SNAC). Bioavailability is only about 1%, requiring much higher doses than injectable
  • BPC-157 — can be taken orally with reduced systemic absorption but good GI tract exposure. See BPC-157 oral vs. injection
  • Collagen peptides — broken down into amino acids and dipeptides that may signal collagen synthesis. Found in peptide supplements

Nasal Peptides

Nasal spray delivery provides decent absorption (10-25% bioavailability) without needles. Used primarily for peptides targeting the brain:

  • Semax — standard nasal delivery, 0.1% solution
  • Selank — nasal spray, commonly 0.15% solution
  • PT-141 — available as nasal spray in some formulations (FDA-approved version is injectable)
  • Oxytocin — technically a peptide, delivered nasally in research settings

Topical Peptides

Applied to skin for local effects. Bioavailability is low for systemic purposes but adequate for skin-specific targets:

  • GHK-Cu — available as serums and creams for skin and hair applications
  • Matrixyl, Argireline — found in cosmetic skincare products
  • BPC-157 — topical formulations for wound healing (limited evidence)

Classification by Regulatory Status

This is where things get complicated — and where most people have questions. The regulatory picture for peptides in the US shifted significantly with the 2026 FDA reclassification. Here’s the current state:

FDA-Approved Peptides

These have gone through full clinical trials and have specific approved indications:

  • Semaglutide (Ozempic, Wegovy, Rybelsus) — type 2 diabetes, obesity
  • Tirzepatide (Mounjaro, Zepbound) — type 2 diabetes, obesity
  • Tesamorelin (Egrifta) — HIV-associated lipodystrophy
  • PT-141/Bremelanotide (Vyleesi) — hypoactive sexual desire disorder in premenopausal women
  • Sermorelin (Geref) — GH deficiency diagnosis/treatment (brand discontinued, still compounded)

These can be prescribed on-label and are covered by some insurance plans.

Prescription Compounded Peptides

Available through compounding pharmacies with a valid prescription. This is how most people access therapeutic peptides. The legality and availability depends on the specific peptide and whether it appears on the FDA’s list of bulk drug substances that can be compounded.

Common compounded peptides: BPC-157, TB-500, CJC-1295, Ipamorelin, GHRP-2, GHRP-6, GHK-Cu, Thymosin Alpha 1, AOD-9604, MOTS-c, Sermorelin, Hexarelin.

The difference between 503A and 503B compounding pharmacies matters here — 503B facilities face more oversight but can produce larger batches without individual prescriptions.

For how to get access: how to get peptides prescribed, do you need a prescription for peptides, and can telehealth prescribe peptides.

Research-Use / Grey Market Peptides

Some peptides are sold as “research chemicals” or “for research purposes only.” These are not intended for human use and carry significant quality and safety risks.

  • Quality varies enormously — no FDA manufacturing oversight
  • Purity may be as low as 50% vs. 99%+ from licensed compounding pharmacies
  • Contaminants, incorrect dosing, and wrong compounds are documented risks

See our comparisons: research peptides vs. prescription, grey market peptides vs. prescription, and are research peptides safe. The bottom line: prescription-grade peptides from a licensed pharmacy are worth the cost difference.

Not Currently Available (Regulatory Restrictions)

The 2026 FDA reclassification placed some previously available peptides in regulatory limbo. Some compounding pharmacies stopped producing certain peptides while the rules were clarified. For the current status of specific compounds: are peptides legal, are peptides legal in the US, BPC-157 FDA status, and is BPC-157 legal.

How to Choose the Right Peptide Type

Start with your goal, then narrow by practical factors:

Goal → Primary Category:

Then consider:

  • Needle tolerance: If you won’t inject, options narrow to MK-677 (oral), Semax/Selank (nasal), GHK-Cu (topical), or oral semaglutide
  • Budget: Peptide therapy cost varies from $50/month (MK-677) to $1,500/month (brand tesamorelin)
  • Evidence level: Semaglutide and tesamorelin have the strongest clinical data. BPC-157 has extensive animal research but limited human trials
  • Regulatory access: FDA-approved peptides are easier to obtain; compounded peptides require a prescribing provider

Our best peptides ranked guide covers top recommendations by category, and the list of peptides is a full reference of every peptide and what it does.

For men specifically: peptides for men. For women: peptide therapy for women.

To get started, find a peptide clinic near you or explore online peptide therapy options. Many providers offer telehealth peptide therapy with home delivery.

FAQ

What are the main types of peptides used in therapy?▼

The seven functional categories are: growth hormone peptides (CJC-1295, Ipamorelin, Sermorelin), weight loss peptides (semaglutide, tirzepatide, AOD-9604), healing peptides (BPC-157, TB-500), anti-aging peptides (GHK-Cu, Epitalon), cognitive peptides (Semax, Selank), immune peptides (Thymosin Alpha 1), and sexual health peptides (PT-141). Most clinical protocols focus on one or two categories based on the patient’s goals.

What types of peptides can you take without injections?▼

MK-677 is oral. Semaglutide comes in oral form (Rybelsus). BPC-157 can be taken orally for gut-targeted effects. Semax and Selank are nasal sprays. GHK-Cu works topically for skin and hair. Collagen peptides are oral supplements. However, most therapeutic peptides are injectable because that’s the most reliable delivery method. See over the counter peptides for what’s available without a prescription.

Are all peptides safe?▼

No blanket answer works here. FDA-approved peptides (semaglutide, tesamorelin, PT-141) have undergone rigorous safety testing. Compounded peptides from licensed pharmacies have good manufacturing standards but less clinical trial data. Research-grade peptides carry the most risk due to quality variability. Side effects vary widely by peptide type — see our peptide side effects guide and are peptides safe for specifics. The biggest risk factor isn’t the peptide itself — it’s the source.

How are peptides different from steroids or SARMs?▼

Peptides are short chains of amino acids that signal the body to do something (release GH, heal tissue, reduce appetite). Steroids are synthetic hormones that directly replace or amplify testosterone and related hormones. SARMs selectively activate androgen receptors. Peptides generally work within the body’s feedback systems; steroids override them. For detailed comparisons: peptides vs. steroids, peptides vs. SARMs, peptides vs. testosterone.

What types of peptides do celebrities and public figures use?▼

Andrew Huberman has discussed GH peptides (Sermorelin, Ipamorelin) and BPC-157 on his podcast — see our Andrew Huberman peptides breakdown. Joe Rogan has spoken about BPC-157 and TB-500 for recovery — covered in Joe Rogan peptides. Most high-profile users focus on GH peptides for anti-aging and healing peptides for recovery.

Sources

  1. Falutz J, et al. “Metabolic effects of a growth hormone-releasing factor in patients with HIV.” N Engl J Med. 2007;357(23):2359-2370. PubMed

  2. Raun K, et al. “Ipamorelin, the first selective growth hormone secretagogue.” Eur J Endocrinol. 1998;139(5):552-561. PubMed

  3. Chapman IM, et al. “Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjects.” J Clin Endocrinol Metab. 1996;81(12):4249-4257. PubMed

  4. Wilding JPH, et al. “Once-weekly semaglutide in adults with overweight or obesity.” N Engl J Med. 2021;384(11):989-1002. PubMed

  5. Heffernan MA, et al. “The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice.” Endocrinology. 2001;142(12):5182-5189. PubMed

  6. Lee C, et al. “The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance.” Cell Metab. 2015;21(3):443-454. PubMed

  7. Sikiric P, et al. “Brain-gut axis and pentadecapeptide BPC 157: theoretical and practical implications.” Curr Neuropharmacol. 2016;14(8):857-865. PubMed

  8. Pickart L, et al. “GHK peptide as a natural modulator of multiple cellular pathways in skin regeneration.” BioMed Res Int. 2015;2015:648108. PubMed

  9. Khavinson VK, et al. “Peptide epitalon activates chromatin at the old age.” Neuro Endocrinol Lett. 2003;24(5):329-333. PubMed

  10. Dolotov OV, et al. “Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus.” Brain Res. 2006;1117(1):54-60. PubMed

  11. Tuthill C, et al. “Thymalfasin: an immune system enhancer for the treatment of liver disease.” J Hepatol. 2004;41(3):s150.

  12. Kingsberg SA, et al. “Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials.” Obstet Gynecol. 2019;134(5):899-908. PubMed

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