Peptides for hair growth: what the evidence shows

People searching for peptides for hair growth usually find the same two names: GHK-Cu, a copper peptide used in skin and scalp products, and TB-500, a synthetic fragment of the protein thymosin beta-4. Scalp serums also list cosmetic peptides with long chemical names. So is there a peptide for hair growth that works in people? On the published evidence, none has been shown to in a trial large enough to be convincing.

What does exist is a small amount of laboratory and animal work, plus one small human trial in which a GHK peptide was combined with another active ingredient ^[3]. That is very different from the multi-year, placebo-controlled trials behind the licensed treatments. This page sets out what each peptide is, what was actually tested, and where the gaps are. It is a research summary, not medical advice, and nothing here suggests using any product. For background on how these compounds are sold, see what research peptides are.

Each hair follicle goes through a repeating cycle. In anagen, the growth phase, cells at the base of the follicle divide rapidly and the hair lengthens; on the scalp this phase lasts for years. In catagen, a short transition, the lower follicle regresses. In telogen, the resting phase, the hair stops growing and is eventually shed as a new anagen hair starts beneath it ^[1]. At any time most scalp follicles are in anagen.

The cycle is controlled by signals between the follicle's epithelial cells, its stem cells in a region called the bulge, and the dermal papilla, a cluster of specialised fibroblasts at the base that acts as a signalling centre ^[1]. Most research on hair peptides targets one of these: making dermal papilla cells grow or survive, activating bulge stem cells, or lengthening anagen.

In pattern hair loss (androgenetic alopecia), follicles gradually shrink under the influence of the hormone dihydrotestosterone, anagen shortens, and thick hairs are replaced by fine ones ^[11]. Other types of hair loss, such as shedding after illness or the autoimmune condition alopecia areata, have different causes. A compound that affects follicle cells in a dish does not necessarily act on any of these processes in a person.

GHK-Cu is a complex of copper with the tripeptide glycyl-L-histidyl-L-lysine, first identified in human blood plasma. In cosmetics it is listed as copper tripeptide-1. It is the peptide most often described as a copper peptide for hair, and the laboratory work people cite is real but narrow.

The study quoted most often did not use GHK-Cu. In 2007, researchers at Seoul National University tested AHK-Cu, which has alanine in place of glycine. At concentrations of 10⁻¹² to 10⁻⁹ M it lengthened human hair follicles kept alive in culture and increased the growth of dermal papilla cells. At the higher concentration it shifted markers of programmed cell death in those cells in a favourable direction, although the fall in the number of dying cells was not statistically significant ^[2]. This is a cell and organ-culture result for a related molecule, not a study of GHK-Cu in people.

The one controlled human trial we found tested GHK with another ingredient. In a 2016 Korean study, 45 men with pattern hair loss applied a complex of 5-aminolevulinic acid and GHK peptide at two strengths, or placebo, once a day for six months. Hair counts rose by 52.6 and 71.5 in the two active groups and by 9.6 in the placebo group. There was no difference in hair length or thickness between groups, and no adverse events were reported ^[3]. Because the product combined two substances, the result cannot be credited to GHK alone, and the abstract describes the GHK peptide rather than the copper complex.

A 2015 review by Loren Pickart, who first described GHK, lists hair follicles among tissues in which GHK has been reported to support healing and growth ^[4]. That review summarises laboratory findings; it does not add a hair trial. We found no controlled trial of a GHK-Cu scalp serum, hair tonic or injection tested on its own. For the wider GHK-Cu evidence on skin and wounds, see the GHK-Cu guide.

Most copper peptides for hair are sold as topical products: serums, scalp tonics and shampoos containing copper tripeptide-1, sometimes with other peptides, caffeine or plant extracts. These are cosmetics. In the UK and EU a cosmetic must be safe for its intended use, but its maker does not have to prove in a clinical trial that it grows hair, and claims to treat a medical condition such as alopecia are not permitted for cosmetics.

Whether GHK-Cu applied to the scalp reaches the follicle in useful amounts is not settled. GHK-Cu is a small, water-loving molecule, and the skin-penetration studies discussed in our GHK-Cu guide were designed for facial skin care, not the scalp. A shampoo that is rinsed off after a minute or two gives any ingredient little contact time.

Research-grade GHK-Cu is also sold as a powder in vials, often with injection in mind. There are no published human trials of injected GHK-Cu for hair or for anything else ^[19]. The FDA has said compounded injectable GHK-Cu may pose a risk of immune reactions because of aggregation and peptide-related impurities ^[13].

Claims about TB-500 hair growth rest on work with a different molecule. Thymosin beta-4 is a natural 43-amino-acid protein that binds actin, part of the cell's internal skeleton. TB-500 is a synthetic seven-amino-acid piece of it, residues 17 to 23 with an acetyl group added (Ac-LKKTETQ). Anti-doping researchers at Ghent University identified this fragment as the active content of products sold as TB-500 ^[6].

The key hair study is Philp and colleagues, published in the FASEB Journal in 2004 by a team at the US National Institutes of Health. They reported that full-length thymosin beta-4 stimulated hair growth in normal rats and mice. In mouse skin, a group of follicle cells originating in the bulge stem cell region produced thymosin beta-4 in step with the hair cycle. In culture, nanomolar concentrations increased the migration and differentiation of follicle stem cells from rat whisker follicles and raised production of the enzyme MMP-2, which remodels the tissue around cells ^[5]. The authors proposed that thymosin beta-4 speeds hair growth partly by helping stem cells and their offspring move to the base of the follicle during anagen.

That is an animal and cell result for the whole protein. No study has tested TB-500 for hair, in animals or in people, and no human hair study of thymosin beta-4 has been published. Whether the seven-amino-acid fragment shares this activity is unknown. A 2024 study found that TB-500 itself did not improve wound closure in cultured cells, while one of its breakdown products did ^[7], which is a reminder that results for the full protein cannot be assumed for the fragment. A 2012 review of thymosin beta-4 by researchers who worked on it for decades summarises its proposed roles in repair and stem cell migration ^[8].

For the rest of the TB-500 evidence, including the difference between the fragment and full thymosin beta-4, see the TB-500 guide. TB-500 is frequently sold alongside BPC-157; what is known about that pairing is covered in BPC-157 and TB-500.

Many hair serums list peptides developed by ingredient manufacturers. The most common are biotinoyl tripeptide-1 (biotin attached to the tripeptide GHK), acetyl tetrapeptide-3, and copper tripeptide-1 (GHK-Cu). Suppliers usually support them with their own laboratory or small consumer studies, which are often not published in peer-reviewed journals and are rarely independent.

We searched PubMed for trials of these ingredients. For acetyl tetrapeptide-3 we found one relevant randomised study, and it tested a blend. In a 24-week Thai trial, 32 men and women with mild to moderate pattern hair loss applied either a combination of biochanin A, acetyl tetrapeptide-3 and ginseng extracts, or 3% minoxidil solution, twice daily. Terminal hair counts rose by 8.3% with the blend and 8.7% with minoxidil, with no statistically significant difference between them. One person using minoxidil developed scalp eczema ^[10]. The study was small, had no placebo group, and used a 3% minoxidil solution rather than the licensed 5% strength, so it cannot show how much, if anything, the peptide contributed.

For biotinoyl tripeptide-1 on its own we found no peer-reviewed controlled human trial. For copper tripeptide-1, the evidence is the GHK work described above ^{[2] [3]}. Marketing phrases such as "clinically proven" on these products usually refer to manufacturer studies that we could not assess. Put plainly, these are cosmetic ingredients with limited independent evidence for hair growth.

Lists of the best peptides for hair growth, or the best peptides for hair growth and thickness, are common on supplier and influencer sites. The published research does not support a ranking. No study has compared GHK-Cu, TB-500 and cosmetic peptides with each other, and none has a trial of the peptide on its own against placebo in people with hair loss.

If the question is which has any human hair data at all, the answer is a GHK peptide, but only in combination with 5-aminolevulinic acid, in 45 men over six months ^[3]. Thickness specifically was measured in that trial and did not differ from placebo ^[3]. Thymosin beta-4 has an animal hair study ^[5]; TB-500 has none. Acetyl tetrapeptide-3 has one small trial as part of a herbal blend ^[10].

Before-and-after photographs on sales pages are not evidence of effect. Hair counts vary with lighting, parting, washing and season, and pattern hair loss itself fluctuates. In the 2016 GHK trial even the placebo group gained an average of 9.6 hairs over six months ^[3], which is why a comparison group matters.

For context only, the two most studied medicines for pattern hair loss are not peptides. Oral finasteride blocks the enzyme that converts testosterone to dihydrotestosterone. In two one-year trials involving 1,553 men aged 18 to 41, finasteride 1 mg a day increased hair counts compared with placebo at one and two years, while men on placebo continued to lose hair ^[11].

Topical minoxidil was tested in a 48-week trial of 393 men. The 5% solution produced more regrowth than the 2% solution and placebo, with more itching and local irritation at the higher strength ^[12]. Both medicines have side effects and suitability questions that a doctor or pharmacist assesses, and they are licensed for particular groups of people.

The point of the comparison is the size and design of the evidence. Finasteride and minoxidil were tested in hundreds to thousands of people against placebo for up to two years. The peptide evidence consists of cell culture, animal work and a handful of small trials of blended products. This page does not suggest using or replacing any treatment; anyone concerned about hair loss can ask a GP or dermatologist, since some causes, such as thyroid disease or iron deficiency, need their own investigation.

GHK-Cu and TB-500 are often sold together in multi-peptide vials. Products called "GLOW" typically combine GHK-Cu, BPC-157 and TB-500, and "KLOW" blends add KPV. They are marketed for skin, hair and recovery. We found no published study of any of these combinations for hair or anything else. What is and is not known about them is set out in Glow and Klow peptide blends.

Blends add a practical problem. A certificate of analysis for a blend has to identify and quantify several peptides at once, and many do not. Our guide on how to read a peptide COA explains what a complete report shows.

In the published topical studies, GHK products were generally well tolerated. The 2016 hair trial reported no adverse events ^[3], and the acetyl tetrapeptide-3 blend caused no local reactions in its trial ^[10]. These studies were small and short, so uncommon or long-term effects would not have been detected. Any scalp product can cause irritation or allergic contact dermatitis.

Injected peptides are a separate matter. There are no human safety data for TB-500 at all, and no published human trials of injected GHK-Cu ^[19]. The FDA has said compounded TB-500 and injectable GHK-Cu may carry risks of immune reactions and of peptide-related impurities ^[13]. A French anti-doping analysis found that products sold online as TB500 and TB1000 did not consistently contain what their descriptions claimed ^[15].

There is also an open question about growth signals. Thymosin beta-4 is found at higher levels in a number of metastatic tumours, and a 2012 review proposed blocking it as a possible cancer treatment ^[9]. That does not show that thymosin beta-4 or TB-500 causes cancer, but no study has tested the question. The long-term effects of repeatedly injecting any of these peptides in people are unknown.

No peptide is approved as a medicine for hair loss in the UK, US, EU, Canada or Australia. GHK-Cu (as copper tripeptide-1) and other cosmetic peptides can be sold in topical products that meet cosmetic rules. Research-grade vials are a different category and are generally not authorised for human use.

In the US, the FDA previously placed both injectable GHK-Cu and TB-500 in category 2 of its compounding policy, the list of bulk substances that may present significant safety risks; the nominations were later withdrawn and both are now listed among substances previously in category 2 ^[13]. TB-500 was considered by the FDA's Pharmacy Compounding Advisory Committee on 23 July 2026; the FDA's meeting page had posted no outcome when we checked ^[17].

The World Anti-Doping Agency lists thymosin beta-4 and its derivatives, including TB-500, under S2, so they are prohibited at all times for athletes in WADA-compliant sport ^[14]. Australia's TGA names GHK-Cu and TB-500 among its examples of unapproved peptide products ^[18], and a Health Canada advisory in April 2026 named both among seized unauthorised peptides ^[16]. Country rules are summarised in our legal status overview, with detail for the UK, Australia and Canada.

PepFinder tracks listings rather than recommending products. You can compare GHK-Cu prices, including GHK-Cu in the UK, and TB-500 prices across stores. Vials, blends and cosmetic serums are priced very differently, so comparing the price per milligram of each peptide is more meaningful than comparing pack prices.

Price is only part of the picture for research-grade products. Our guides on how to spot a fake peptide supplier and third-party peptide testing cover the checks that matter, and the list of third-party tested suppliers shows stores that publish independent results. The peptide calculator converts vial contents to concentrations but does not indicate any appropriate amount, and our guide to storing peptides covers how powders are usually kept.