Read this first
This is plain-language harm-reduction information, not medical advice. Peptides discussed here are research compounds; most are not approved for human use. People will use them either way — we would rather they have the facts.
Research peptides are short chains of amino acids made in laboratories and sold, mostly without a medical licence, labelled as 'for research use only'. Some are copies of natural signalling molecules, some are modified versions, and a few are the active ingredients of licensed drugs. The label tells you about how they are sold, not about whether they are safe or effective.
What is a peptide?
Amino acids are the building blocks of proteins. Join a few together in a chain and you get a peptide. There is no sharp official line, but a rough rule of thumb is that anything up to about 50 amino acids is a peptide and anything bigger is a protein. BPC-157 has 15 amino acids. GHK-Cu has only three, bound to a copper ion.
Your body already makes thousands of peptides. Many act as messengers: they are released in one place, travel through the blood or tissue, and tell cells somewhere else what to do. That is what makes them interesting to researchers and, inevitably, to people hoping to borrow those signals.
Peptide, protein, hormone, small molecule: how they overlap
These words describe different things and are often muddled:
- Peptide vs protein: mostly size. Peptides are short; proteins are long and fold into complex shapes.
- Hormone: a job description, not a size. A hormone is any messenger made in one part of the body that acts elsewhere. Some hormones are peptides, some are proteins, and some are neither (testosterone is a steroid).
- Small-molecule drug: a conventional pharmaceutical with a low molecular weight, like paracetamol or most pills. Peptides are generally bigger and more fragile, and many are broken down in the gut, which is why many are injected.
- Growth factor: a signalling protein or peptide that tells cells to grow or divide. Some compounds on this site, such as IGF-1 LR3, fall into this group.
A few things sold alongside peptides are not really small peptides at all. HCG and human growth hormone are large protein hormones. They get grouped in because they are injected and sold in similar ways.
Why is everything labelled 'research use only'?
Most of these compounds have never been approved as medicines. Selling an unapproved product for people to inject would bring regulatory trouble, so sellers label vials as lab materials. In reality, plenty of buyers are individuals, not laboratories. The label does not mean the product has been tested for human safety, and it does not guarantee purity. Our article on whether peptides are legal in the UK goes into this in more depth. It is general information, not legal advice.
What does the evidence look like?
It varies enormously, and this is the part most worth being honest about.
- Licensed, well-studied: semaglutide and similar drugs have large human trials behind them, for specific conditions, in prescribed doses.
- Some human data, limited: a few compounds have small trials or old clinical use.
- Mostly animal or cell studies: the majority of popular 'healing' peptides, including BPC-157, are in this group. Results in rats do not reliably predict results in people.
- Anecdote only: forums and social media. Useful for spotting side effects, unreliable for proving benefit.
Each peptide page on this site tries to separate those levels so you can see what is known and what is not.
The main categories on this site
The site groups compounds by what people usually use them for. A summary:
- Healing and recovery: such as BPC-157 and TB-500.
- Growth hormone secretagogues: compounds that prompt the pituitary to release growth hormone, such as ipamorelin and CJC-1295.
- GLP-1 and metabolic: weight and blood-sugar drugs such as semaglutide, tirzepatide and retatrutide.
- Tanning and libido: Melanotan II and PT-141.
- Cognition, sleep and mood: such as Semax, Selank and DSIP.
- Skin, cosmetic and longevity: GHK-Cu, epithalon and similar.
- Hormonal, immune and blends: HCG, thymosin alpha-1 and pre-mixed combinations.
If you are not sure where to begin, Find your goal groups compounds by what you are trying to understand.
Natural, synthetic and modified: what those words mean
Almost all research peptides are made synthetically, by building the chain one amino acid at a time. 'Synthetic' does not mean fake or dangerous; it simply means made in a lab rather than extracted. Some are exact copies of natural sequences. Others are modified to last longer in the body, resist breakdown or bind more strongly, and those changes are exactly why a modified version can behave very differently from the natural molecule it came from.
You will also see 'lyophilised' on listings. That just means freeze-dried: the peptide arrives as a dry powder in a sealed vial and is mixed with sterile liquid before use, which is covered on each compound's page.
Why quality is the big unknown
Because these products are not made under medicine regulations, purity, dose and sterility are not guaranteed. A vial can contain less than it says, more than it says, a different compound or contaminants. Independent third-party testing helps but does not remove the uncertainty. See safer use basics for practical harm-reduction steps.
'Peptide' describes a molecule's size, not its safety. Natural and synthetic peptides can both cause real harm at the wrong dose or from the wrong source.
Bottom line
Research peptides are short amino-acid chains sold mostly outside the medicine system. A few have solid human evidence; many have only animal data or anecdote. 'Research use only' is a sales label, not a quality standard. Understanding what a compound is, what is actually known about it, and where the gaps are is the best place to start.
Common questions
What is the difference between a peptide and a protein?
Mainly length. Peptides are short chains of amino acids, usually under about 50, while proteins are longer and fold into more complex shapes. The boundary is a rule of thumb rather than a strict rule.
Are research peptides the same as steroids?
No. Steroids such as testosterone are fat-derived molecules, while peptides are chains of amino acids. They work through different mechanisms, although some peptides affect natural hormone levels.
Are research peptides approved for human use?
Most are not. Some peptide-based drugs, like semaglutide, are licensed medicines, but the research-labelled versions of most others have never been approved for any human use.
Why are peptides injected instead of swallowed?
Many peptides are broken down by stomach acid and digestive enzymes before they reach the blood, so injection (or sometimes a nasal spray) gets more into the body. A few are designed to survive oral use, but they are the exception.