TL;DR.

A peptide is a short chain of amino acids — between 2 and ~50. Above that, it's a protein. Your body makes thousands of them naturally. Insulin is a peptide. Oxytocin is a peptide. The pituitary spends most of the day making peptide hormones.

When we say "peptide" on this site, we mean a synthetic or semi-synthetic peptide that someone is injecting (or applying topically) for a non-trivial reason — weight loss, recovery, sleep, skin, longevity, libido, cognition. Some are FDA-approved drugs. Some are RUO research chemicals. Some are 503A-compounded with a real prescription. The catalog has all 59.

Most peptide content online flattens evidence quality. We don't. Of the 59 in our catalog, only 23 have a published human trial we can ratio-check doses against. 9 have rodent data only. 27 are community-extrapolated — meaning the dose people use comes from forums, not papers.

We tag every peptide with its evidence species and link the source citation. When the species is rodent or extrapolated, the Stack Builder refuses to pre-fill a dose and the safety check disables the ratio comparison. You get an honest "no human reference" warning instead of a fake number that looks authoritative.

The same molecule (semaglutide, say) can cost you $1,400/mo or $5/mo depending on which tier of the supply chain you buy from. Same compound, often the same factory, different markup.

1. Tier 1 · Gray market · raws direct from overseas factories, $5–$15/mo, Discord-coordinated, crypto only, customs risk.
2. Tier 2 · US RUO · resellers vialing the same raws, $25–$80/mo, "research only" labels, COA varies.
3. Tier 3 · Compounded · 503A pharmacy, $40–$300/mo, real prescription, real pharmacist.
4. Tier 4 · FDA Brand · pharmacy + insurance, $1,000–$1,500/mo list, manufacturer coupons help.

We don't endorse a tier. We name the trade-offs. Read the full sourcing guide →

1. 1. Mg vs mcg is the #1 way people overdose. 1 mg = 1,000 mcg. A 5mg vial holds 5,000 mcg. A typical "250 mcg" community dose is 1/20th of the vial. Confuse the units, overdose by 1000×.
2. 2. Trial dose ≠ community dose. The number in the published paper is rarely the number people actually inject. Trial doses are usually higher (efficacy testing) or in a different route. Community doses are extrapolated from rodent studies or settled by Reddit consensus. We label both.
3. 3. Use the calculator. Vial size + dose + syringe → exact units. The math is trivial when you're awake; it gets dangerous at 11pm. Open the recon calculator →

The 59 compounds in our catalog cluster into about 10 mechanism families. The big ones:

• GLP-1 agonists · Tirzepatide, Semaglutide, Retatrutide. Weight loss, diabetes.
• GH secretagogues · CJC-1295, Ipamorelin, Sermorelin, MK-677. Sleep, recovery, body comp.
• Mitochondrial · MOTS-c, SS-31, NAD+, Humanin. Energy, longevity research.
• Recovery / immune · BPC-157, TB-500, KPV, Thymosin-α1. Tendons, gut, immune modulation.
• Copper tripeptides · GHK-Cu, AHK-Cu. Skin elasticity, hair regrowth, wound healing.
• Melanocortins · Melanotan I/II, PT-141. Pigmentation, libido.
• Nootropic · Selank, Semax, Cerebrolysin, Dihexa. Anxiety, focus, neuroprotection.
• Khavinson tetrapeptides · Epitalon, Vesugen, Pinealon, Cortagen. Russian longevity research.

Browse the full library →

If you've never touched a peptide, three honest entry points:

• → Take the 5-question quiz · pick a goal, get 3 starter stacks ranked by fit.
• → Read "How to dose" · the trial-vs-community frame is the most important concept on the site.
• → Browse the library · filter by goal, evidence species, status. Click any card for the deep dive.

We're not your doctor. We don't sell peptides. We don't take vendor money. We just read the papers and tell you what we find — including the safety signals the vendor sites won't surface.