Peptides 101: The 10 Categories of Peptides
10.1 million US searches per month. 10 distinct categories. One guide that maps the whole peptide universe — what each does, the proven compounds, and where to start.
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How It Works
The most clinically validated category. GLP-1 agonists slow gastric emptying, curb appetite, and shift insulin sensitivity. Semaglutide (Ozempic/Wegovy) and tirzepatide (Mounjaro/Zepbound) are FDA-approved. Retatrutide (LY3437943) — the triple agonist now in Phase 3 — is showing ~24% weight loss at 48 weeks.
GHRH/GHRP analogs trigger endogenous GH release without the suppressive feedback of exogenous HGH. CJC-1295 + Ipamorelin is the most popular off-label stack. Sermorelin is the classic clinic-prescribed GHRH. Tesamorelin is the only FDA-approved GHRH analog (for HIV-associated visceral fat) — strongest human evidence in this category.
The "Wolverine stack" — used off-label for tendon, joint, and gut repair. BPC-157 (a pentadecapeptide from gastric juice) and TB-500 (a thymosin beta-4 fragment) are the workhorses. Strong animal data; small human trials. See BPC-157 vs TB-500 for the comparison.
GHK-Cu (copper tripeptide-1) is the standout — naturally occurring, used in dermatology since the 1970s. Stimulates collagen, reduces visible aging, and accelerates wound healing. Topical forms are FDA-cleared as cosmetics; injectable use remains research-grade.
Russian-developed nootropic peptides — short, peripherally-administered, surprisingly fast-acting. Semax (ACTH 4-7 analog) for focus and stress resilience. Selank (tuftsin analog) for anxiolytic effect without sedation. Both are approved drugs in Russia; off-label everywhere else.
These target the cell's power plants directly. MOTS-c (a mitochondrial-derived peptide) regulates metabolic homeostasis and shows ~12× endurance effects in aged mice. SS-31 (elamipretide) protects cardiolipin and is in Phase 2 cardiac trials.
Pineal bioregulators developed in St. Petersburg over four decades. Epitalon targets telomerase activation and circadian/melatonin rhythm. Pinealon is the cognitive-aging variant. See the synergy protocol for the most-cited stacking approach.
Thymosin Alpha-1 is the only category-defining peptide here — a 28-amino-acid thymus-derived immunomodulator approved in 30+ countries for hepatitis B/C, sepsis, and as adjunct cancer therapy. Not FDA-approved in the US but extensively studied.
Overlaps with category 3 but worth separating. BPC-157 has the strongest gut-repair signal (originally isolated from gastric juice). KLOW and GLOW are skin/healing blends that include GHK-Cu and pentapeptide healing fragments. For IBD, ulcers, and leaky-gut protocols, see our joint/gut healing guide.
Beyond GLP-1s — adjunct compounds that complement weight-loss stacks. AOD-9604 (an HGH fragment) targets fat metabolism without GH side effects. Cagrilintide (amylin analog) pairs with semaglutide as CagriSema — early Phase 3 data shows ~22.7% weight loss.
What the Data Shows
Key Takeaways
- Peptides are short amino-acid chains (typically 2-50) that act as signaling molecules in the body
- The 10 categories map to specific bodily systems — pick by goal, not hype
- Weight-loss GLP-1s (semaglutide, tirzepatide, retatrutide) have the strongest human clinical data
- Tesamorelin is the only FDA-approved GHRH analog (for HIV-associated visceral fat)
- Thymosin Alpha-1 is approved in 30+ countries — internationally validated immune modulation
- Stacking peptides from different categories often outperforms single-compound use
- Storage matters: bacteriostatic water, refrigeration after reconstitution, used within ~30 days
- Long-term safety (>5 years) of newer GLP-1s outside obesity/diabetes trials
- Optimal off-label dosing for healing peptides (BPC-157, TB-500) in humans
- Whether oral peptide forms reliably achieve meaningful systemic absorption
- Direct head-to-head comparisons between most peptides within the same category
- How stacking affects hormone feedback loops (especially the GH axis with multi-GHRP stacks)
- Whether longevity peptides (epitalon, pinealon) actually extend human lifespan
Frequently Asked Questions
What are peptides?
Peptides are short chains of amino acids — typically 2 to 50 in length — that act as signaling molecules in the body. They tell cells to release hormones, repair tissue, modulate immunity, or activate metabolic pathways. Insulin, oxytocin, and ghrelin are all peptides. The peptides in this guide are research-grade compounds used off-label (in most cases) for specific functional goals: fat loss, healing, cognition, longevity.
Are peptides legal?
It depends on the peptide and the jurisdiction. FDA-approved peptides like semaglutide (Ozempic), tirzepatide (Mounjaro), tesamorelin, and sermorelin are legal with a prescription. Research-grade peptides like BPC-157, TB-500, MOTS-c, and the GHRPs are not FDA-approved for human use; they are sold legally for research purposes only in the US. Semax and Selank are approved drugs in Russia. Possession laws vary — always check your local regulations.
Which peptide should a beginner start with?
For weight loss: a prescribed GLP-1 (semaglutide or tirzepatide) is the most evidence-backed choice. For healing or joint pain: BPC-157 is the most common entry point. For sleep and recovery: a CJC-1295 + Ipamorelin stack delivered before bed. Don't start with three peptides at once — pick the single category that matches your top goal and run it cleanly for 8-12 weeks before stacking. See our full beginner's guide for protocols.
Can you stack peptides from different categories?
Yes — stacking is the rule, not the exception, in advanced protocols. Common stacks: BPC-157 + TB-500 for synergistic healing; CJC-1295 + Ipamorelin for natural GH pulses; Semax + Selank for daytime focus + evening calm; Epitalon + Pinealon for longevity. The key rules: don't combine two peptides that hit the same receptor (e.g. two GHRPs), give each compound 2-4 weeks of solo use before adding another so you can attribute effects, and keep total injection volume reasonable.
How do you store peptides safely?
Lyophilized (powder) peptides are shelf-stable for years at room temperature, but should be refrigerated for long-term storage and frozen for >12-month holds. After reconstitution with bacteriostatic water, most peptides are stable for 28-30 days refrigerated (2-8°C / 36-46°F). Avoid repeated freeze-thaw cycles, direct light, and shaking the vial. Reconstitute by trickling the bac water down the side of the vial — don't spray directly onto the powder.
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Educational purposes only. Not medical advice.
Speak with a licensed healthcare provider before using any peptide.
Off-label peptide use carries unquantified long-term risks. This guide summarizes published research, not clinical guidance.