What Peptides Are Used For: An Index

What Peptides Are Used For: An Index of This Library, by Purpose

Every compound in this library grouped by what it is sold for — and a count of how many are approved by any regulator anywhere. Nine of sixty, and six of those nine are approved for something other than the use they are sold for.

Caroline S · Published 2026-09-18

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This is an index, not a recommendation. It groups every compound entry in this library by the purpose it is sold or studied for, and links to the entry that sets out what each one actually is. What it deliberately does not do is tell anyone which to choose — that boundary is what keeps a reference useful.

Two counts are worth having before the list.

Sixty compounds, nine approvals

On 2026-09-18 this library held 60 compound entries. Nine of them — 15% — are approved by a regulator somewhere for at least one indication. The other 51 are not approved as medicines anywhere; they are sold under research-use-only terms, as cosmetic ingredients, or through compounding pharmacies.

That ratio is the first thing a reader should have. But the second is more useful.

Six of the nine are approved for something else

Approval attaches to an indication, not to a compound. Lining each approved compound's actual approval up against the purpose it is commonly sold for, the two match in only three cases.

Compound	Approved for	Commonly sold for	Same?
Semaglutide	Type 2 diabetes, weight management, cardiovascular risk	Weight loss	✓
Tirzepatide	Type 2 diabetes, weight management, sleep apnoea	Weight loss	✓
PT-141	Hypoactive sexual desire disorder	Sexual function	✓
Tesamorelin	Excess abdominal fat in HIV lipodystrophy	General fat loss, growth hormone	✗
Oxytocin	Starting or strengthening labour contractions	Bonding, social effects	✗
hCG	Ovulation induction, hypogonadotropic hypogonadism, undescended testicles	Weight loss — which its label rejects	✗
Triptorelin	Advanced prostate cancer, central precocious puberty — both suppressing hormones	Restarting hormones after a cycle	✗
Melanotan I	Pain-free light exposure in erythropoietic protoporphyria	Cosmetic tanning	✗
GHRP-2	A diagnostic test of pituitary function (Japan)	Muscle, recovery, fat loss	✗

An approval is frequently cited as though it settled a question it was never asked. GHRP-2's is the sharpest case: the single approval anywhere is for a test that measures whether a pituitary responds — a use that requires the hormone spike to be large and reliable once, and says nothing about repeating it for months.

The index, by purpose

Not taken for anything, or not peptides

C-peptide — a diagnostic measurement · NAD+ — a dinucleotide coenzyme · GLP-3 — a name for something that does not exist in humans · Larazotide — a trial-stage drug candidate · ARA-290 — investigated for nerve damage

What the grouping does not tell you

A compound appearing under a purpose means it is sold or studied for that purpose. It does not mean it does it, and in several cases here no human being has ever been given the compound in a registered study at all.

Each entry states its own evidence position: how much is human and how much is animal, how many studies exist, what those studies actually administered, and what remains unknown. That is where the answer to "does it work" lives, one compound at a time. The foundations of what these molecules are, and what the word peptide covers, are worth reading first if any of this is new.

Counts on this page were taken on 2026-09-18 and are refreshed as entries are added.

Frequently asked questions

What are peptides used for?

In approved medicine, for a set of specific and mostly narrow indications: type 2 diabetes and weight management, certain hormone-driven cancers, labour induction, a rare light-sensitivity disorder, fertility treatment, and a few others. Outside approved medicine they are sold for a much wider range of purposes — healing, muscle growth, fat loss, sleep, skin, cognition, immunity, tanning and longevity. This page indexes both, grouped by purpose, and links to the entry for each compound.

How many peptides are actually approved as medicines?

Of the 60 compound entries in this library on 2026-09-18, nine are approved by a regulator somewhere for at least one indication — about 15%. They are semaglutide, tirzepatide, tesamorelin, triptorelin, oxytocin, hCG, PT-141, melanotan I and GHRP-2. The other 51 are not approved as medicines anywhere.

Are the approved ones approved for what they are sold for?

Usually not. Only three of the nine — semaglutide, tirzepatide and PT-141 — are approved for something close to the use they are commonly marketed for. The other six are approved for a different purpose entirely: GHRP-2's only approval is a diagnostic test, hCG's label rejects the weight-loss use it is best known for, triptorelin's approvals switch hormones off rather than restart them, melanotan I is approved for a rare light-sensitivity disorder rather than tanning, oxytocin's approval is obstetric, and tesamorelin's is a single narrow indication in HIV lipodystrophy.

Which peptide is best for muscle, or weight loss, or healing?

This library does not answer that question, by design. It is organised by compound rather than by reader: each entry sets out what one substance is, what it is claimed to do, and what the evidence for it consists of. Ranking products and recommending choices is a different job, done by different publications, and mixing the two would make both less reliable.

Why are some things in this library not peptides?

Because people search for them using peptide vocabulary, and saying so plainly is more useful than omitting them. NAD+ is a dinucleotide coenzyme with no amino acids in it. Orforglipron is an 883-dalton small molecule that acts on a peptide hormone's receptor. Noopept is a prodrug. Each of those entries states in its first line that the compound is not a peptide.

Does a peptide having a purpose mean it works for it?

No, and keeping those apart is the point of the grouping on this page. A purpose is what a compound is sold or studied for; whether it does it is a separate question that each entry addresses on its own evidence. Several compounds here are widely sold for uses in which no human study has ever administered them.

How is this list kept current?

The library is reconciled against its compound roster every week, so that a compound with no entry is queued and an entry not checked for 180 days is queued for refresh. The counts on this page carry the date they were taken, and they change as entries are added.

What Peptides Are Used For: An Index of This Library, by Purpose

Sixty compounds, nine approvals

Six of the nine are approved for something else

The index, by purpose

Weight, appetite and metabolism

Growth hormone

Muscle growth and muscle preservation

Healing, tendon and connective tissue

Skin and appearance

Sleep

Focus, mood and cognition

Immune function

Sexual and reproductive

Skin pigmentation

Longevity and mitochondria