The Peptide Transparency Database
Peptides, explained by the evidence
Peptides are short chains of amino acids. The word covers everything from insulin to collagen powder to unapproved injectables, and what the studies show is very different for each. Start here for the basics, then go as deep as you like.
What are peptides?Browse 26 study summaries
This site is run by an employee of Pürblack, a peptide supplement brand, in a personal capacity. Pürblack does not fund, review or direct the site, and its costs are paid by its operator.
The basics
What are peptides?
Amino acids link into chains. Long, folded chains are proteins; short ones are peptides. There is no sharp line between the two, and the cut-off varies by source.
Read the full explainer or see the glossary.
The mechanism
How do they work?
Three ideas cover most of it.
Some are signals
They attach to a receptor on a cell and change what it does. That is how peptide drugs such as insulin are designed to act.
Swallowed ones meet digestion
Whether anything active gets through, and does anything, is a question for trials, not for the label.
Publications found by a 2026 scoping review of six popular injectable peptides (Tewari 2026)
A mechanism is not proof
“It blocks an enzyme” is a reason to run a trial, not a result.
The landscape
What are the different types?
We sort them by what matters to a reader: whether they are approved, and how much human evidence exists.
Approved prescription drugs
Insulin and the GLP-1 medicines are peptide drugs. A 2026 review contrasts them with a parallel “gray market” of unapproved compounds (Mendias & Awan). Prescribed by a clinician.
Collagen and marine peptide supplements
Fragments of collagen or fish protein, swallowed as powders and capsules. Skin has the most trials; other uses are small or mixed. Do oral marine peptides work?
Skin-care peptides
Peptides such as GHK-copper are applied to the skin. This hub holds a review of GHK but no controlled trial of a product yet.
Unapproved wellness and research peptides
BPC-157 and similar compounds are not FDA-approved for any use (systematic review), and their compounding status changed through 2026. Legal status
What we know
Are peptides safe?
There is no single answer, because “peptides” is not a single thing. Here is what we know, by type.
Approved prescription drugs
Safety reviewed at approval
Approval includes a review of safety, and they are used under a clinician. They still have side effects; this site has not summarised the trial evidence for any approved peptide drug.
Collagen and marine supplements
Not assessed here yet
One small trial reported no adverse effects over four weeks in 29 people (Kawasaki 2000), which is too few to establish safety.
Skin-care peptides
Not assessed here yet
No safety evidence is summarised on this site for topical peptides.
Unapproved wellness and research peptides
Human data scarce
Reviews say rigorous human safety data are scarce and serious harm is possible, and warn of risks from unregulated manufacturing and contamination.
The evidence
Do they work? The evidence at a glance
For each topic, the best-supported and the least-supported claim we have summarised. Open a topic for every rating.
How to read the meters
Not yet assessed here
No human trials found
Mostly animal evidence
Limited human evidence
Mixed human results
Consistent in human trials (with caveats)
The dashed fifth segment is always empty: it is reserved for large, independent, replicated human trials that agree, and we have not rated anything that high. “Mixed” and “Limited” share a step because they differ in kind, not in depth. Safety ratings are shown as words only, because a meter beside “limited safety data” could be misread as “safe”.
Peptides for skin & anti-aging
Best supported
Oral collagen peptides
Least supported
Oral marine (fish-derived) collagen peptides
3 ratings (1 not yet assessed), reviewed November 9, 2026
Peptides for muscle & strength
Best supported
Oral collagen peptides with resistance training
Least supported
Injectable and research peptides (BPC-157, CJC-1295, ipamorelin and others)
3 ratings, reviewed November 9, 2026
Peptides for joints & tendons
Best supported
Oral collagen for osteoarthritis symptoms
Least supported
Oral marine (fish-derived) collagen peptides for joints and tendons
3 ratings, reviewed November 9, 2026
Marine peptides for blood pressure & vessels
Best supported
Valyl-tyrosine, a defined sardine-derived peptide
All 3 assessed ratings sit at this level.
3 ratings, reviewed November 9, 2026
Marine peptides for sleep, memory & stress
Best supported
Fish hydrolysate for sleep quality
All 3 assessed ratings sit at this level.
3 ratings, reviewed November 9, 2026
Thymic peptides for immune function
Best supported
Thymus extracts added to cancer treatment
Least supported
Thymalin and engineered thymosin alpha-1 in animals
4 ratings (1 not yet assessed), reviewed November 9, 2026
Peptide safety & regulation
Rating
BPC-157 (unapproved)
All 2 assessed ratings sit at this level.
2 ratings, reviewed November 9, 2026
Ratings reflect only the studies summarised here. How ratings are set.
Regulation
Are peptides legal?
It depends on the peptide and how it is made and sold. Some are FDA-approved drugs; many popular wellness peptides are not approved for any use. In July 2026 an FDA advisory committee considered seven of them for the compounding bulks list, and according to news reports it recommended 6.
29 Sep 2023
FDA adds several peptides to Category 2 of its interim compounding policies.16 Apr 2026
FDA announces a public advisory committee meeting on the 503A bulks list.23–24 Jul 2026
The committee considers seven peptides. News reports say it recommended 6.November 9, 2026
Last checked. We found no final FDA action.
A skill to keep
How to judge a peptide claim
Five questions we ask of every study. They work on ads and social media posts too.
- 1
Was it tested in people?
Results in animals or cells often do not carry over.
- 2
Was there a comparison group?
A placebo group shows what happens without the treatment.
- 3
Did it measure a real outcome?
A blood marker is not the same as feeling or functioning better.
- 4
How big was it, and how long?
A few dozen people over a few weeks can only suggest an effect.
- 5
Who paid for it?
Company ties do not make a result wrong, but they should be stated.
Common questions
Do peptides work?
It depends on the peptide and the claim. Oral collagen peptides have consistent but caveated human evidence for skin hydration and elasticity. Most injectable wellness peptides, such as BPC-157, have mostly animal evidence (Tewari 2026). See the evidence grid above.
Is swallowing a peptide different from injecting it?
Yes. Swallowed peptides meet digestion, so whether an oral peptide has any effect is a question for trials. Injected peptides skip digestion but carry injection risks and depend on how the product was made. How peptides work
Where do the study summaries come from?
Each summary is written in our own words from the study's abstract, and its identifiers are checked against PubMed. Each one states what the study cannot show and who paid for it, or that funding is not stated. Methodology
How do I tell whether a peptide claim is solid?
Ask whether it was shown in people, animals or cells; whether the study had a comparison group; whether it measured a real outcome or only a marker; and who paid for it. See the checklist above.
Why trust this site
26
studies summarised from their abstracts, each with what it cannot show
7
evidence topics, each with a dated verdict
Open
dataset, free to download as CSV and JSON
Public
Who runs this site and how it is funded: About this site. Last reviewed November 9, 2026.