Peptides for hair growth: what the trials show and what works better

No peptide is approved to treat hair loss, and none has trial evidence close to the two drugs that are. Copper peptides, biotinoyl tripeptide-1 and acetyl tetrapeptide-3 appear in many serums, backed by lab data and a handful of small, short studies, many tied to the companies that make them. Finasteride and minoxidil have multi-center, placebo-controlled trials and FDA labels. This goal sits with the others in the peptides by goal index.

What people hope for, and what the studies measured

People searching this want new hair where it has thinned, ideally without a daily drug and its side effects. Peptide studies rarely test that directly. Some count hairs in a tiny circle of scalp. Others report the ratio of growing to resting hairs, or the share of thick hairs. Those can move without visible new coverage, and a 2026 review pointed out that peptide studies use so many different measures that results are hard to compare. It called whether a treatment enables normal hair growth in bald areas the measure that matters most.

Compare that with finasteride’s two-year trials, which counted hairs in a fixed scalp area and added an expert panel’s review of photographs.

Do copper peptides work for hair?

Copper peptides are still a laboratory finding for hair. A 2007 Seoul National University study found that the copper tripeptide AHK-Cu, at very low concentrations, lengthened human hair follicles kept alive outside the body and made the cells at the follicle’s base multiply. A 1993 primate-center review reported that a copper-binding peptide enlarged follicles on fuzzy rats, an effect similar to topical minoxidil. A 2026 systematic review of GHK-Cu lists pattern hair loss among the uses that still need well-designed human trials.

The study many websites cite as a human GHK-Cu hair trial needs a closer look. In 2016, Korean researchers gave 45 men a scalp spray containing GHK joined to 5-aminolevulinic acid, at 50 or 100 mg/mL, or a placebo, once daily for 6 months. Counted in a 1 cm circle, hair rose by 71.5 and 52.6 against 9.6 on placebo. The lower dose did better than the higher one, and hair length and thickness did not differ between groups. The paper describes GHK with no copper, and its chemical formula contains none, so it is not a test of a copper peptide serum. The topical GHK-Cu evidence is mostly about skin, and the copper peptide serum guide covers what to check on a label.

Biotinoyl tripeptide-1, acetyl tetrapeptide-3 and others

Biotinoyl tripeptide-1 is GHK with biotin attached, best known as part of Procapil, a cosmetic ingredient that also contains apigenin and oleanolic acid. A 2025 review in the International Journal of Trichology described a pilot placebo-controlled study in 35 men using a 3% lotion for 4 months, which reported a better ratio of growing (anagen) to resting (telogen) hairs, and a 6-month open-label study of 56 patients with no control group. The review’s verdict on these and similar actives: small samples, “conflicts of interest in the form of sponsorship,” and “a lack of head-to-head comparison with the standard methods of treatment.”

Acetyl tetrapeptide-3 is the peptide in the ingredient Capixyl. We found two human studies, and both tested mixtures. In 2013, a study of 30 volunteers over 4 months reported a 46% rise in the growing-to-resting ratio with a red clover and peptide mixture, against a 33% fall on placebo. The corresponding author worked for the cosmetics company behind the ingredient. In 2020, a 32-person trial found no significant difference between an herbal combination and 3% minoxidil, but 32 people is far too few to show that two treatments are equal.

Two more peptides have reached people. The pentapeptide Gly-Pro-Ile-Gly-Ser raised the share of thick hairs in a 22-man Shiseido study. Water-soluble chicken egg yolk peptides, taken by mouth at 250 mg a day, gave higher hair density than placebo after 24 weeks in a 76-person study of women, according to a 2026 review. Authors of the original paper included staff of two companies.

What the best recent review concluded

A 2026 review in Biomedicines surveyed peptides for hair loss and was blunt about the gap. Most data come from cell cultures and mice. The clinical studies of acetyl tetrapeptide-3 and the pentapeptide lacked enough participants, and the human studies it reviewed did not offer meaningful comparison with minoxidil or finasteride, “which undermines their credibility.” It also noted that peptides pass poorly through skin and that immune reactions to them still need proper study in people.

One larger test is underway. A randomized, double-blind trial in Bangkok is comparing a peptide hair serum with 2% minoxidil in about 80 adults over 24 weeks, with a cosmeceutical company as collaborator and hair count as the main outcome. The registry lists it as recruiting as of this update, with no results posted, so it says nothing yet.

Why the approved drugs win on evidence

Size and length explain most of the gap, more than any failure of peptides. Finasteride’s trials enrolled 1,553 men and ran for two years. Minoxidil’s 393-man trial ran 48 weeks against both placebo and a lower dose. No peptide hair study comes close. Drug makers fund their own trials too, but FDA then reviews the data. A cosmetic serum has no such step. On the ladder below, peptides for hair sit on the small human studies rung, while finasteride and minoxidil have reached the top.

The American Academy of Dermatology (AAD) says the earlier treatment starts, the more likely regrowth is. It also says minoxidil tends to work better alongside another treatment.

Finasteride safety

Beyond the trial rates above, the Propecia label lists these reports from general use: sexual dysfunction that continued after stopping, male infertility or poor semen quality, testicular pain, breast tenderness and enlargement, male breast cancer, and depression, suicidal ideation and suicidal behavior. Finasteride lowers PSA, a prostate cancer blood test, so anyone taking it should tell the clinician reading that test. In a long study of a 5 mg dose, high-grade prostate cancer occurred in 1.8% against 1.1% on placebo; the label says the meaning for the 1 mg dose is unknown. Anyone with low mood or thoughts of self-harm while taking finasteride should contact a clinician promptly. In a crisis in the US, call or text 988, at any hour.

Minoxidil safety

The women’s Drug Facts label says not to use it if hair loss is sudden or patchy, if there is no family history of hair loss, if the reason is unknown, if it follows childbirth, if the scalp is red, inflamed, infected or painful, or under age 18. It says to ask a doctor first with heart disease. It tells users to stop and ask a doctor for chest pain, rapid heartbeat, faintness or dizziness, sudden unexplained weight gain, swollen hands or feet, scalp irritation, unwanted facial hair, or no regrowth at 6 months. It also warns that minoxidil may be harmful during pregnancy or breastfeeding, and that shedding may continue for up to 2 weeks after starting, which it calls temporary. The label says it will not work for all women.

Compounded and off-label versions

Two versions sold for hair are not FDA-approved for it. Compounded topical finasteride has no approved formulation. In an alert dated April 2025, FDA described 32 adverse event reports from 2019 to 2024, including erectile dysfunction, anxiety, suicidal ideation, brain fog and depression, and most reports said the effects continued after stopping. Some patients said they had been told a topical carried no risk. FDA also warned that women could be exposed through contact with the applied product.

Oral minoxidil is a blood pressure tablet that some prescribers use off-label for hair. Its label carries a boxed warning for pericardial effusion, fluid around the heart, and says use to promote hair growth “is not an approved indication.” That warning was written for severe high blood pressure. Hair doses are lower, but an analysis of FDA adverse event reports still found a pericardial effusion signal at every dose range it checked, up to 10 mg. Those reports cannot prove the drug was the cause. Its authors recommended the lowest effective dose. Both products are worth a direct conversation with a prescriber about risk.

What else do dermatologists offer?

The AAD lists several options besides minoxidil and finasteride. It says spironolactone is effective in about 40% of women with female pattern hair loss. Laser therapy is described as safe and painless but needing many sessions. Platelet-rich plasma, injections made from a patient’s own blood, usually starts monthly for 3 months and continues every 3 to 6 months. A hair transplant is described as an effective and permanent solution for pattern baldness.

Is it really pattern hair loss?

Treatment depends on the cause, so that comes first. The AAD says losing 50 to 100 hairs a day is normal. Heavy shedding can follow surgery, high fever, chemotherapy or childbirth, and hereditary hair loss is more common than infection. Hairstyles that pull, ringworm and alopecia areata are other causes. A dermatologist may order a blood test or scalp biopsy.

See a clinician rather than trying a serum if hair falls out suddenly or in patches, if the scalp is red, sore or scaly, or if you cannot tell why it is happening. The minoxidil label excludes those situations for the same reason.

For women

Finasteride is not indicated for women. Its label contraindicates it in women who are or may become pregnant, because it can cause abnormalities of the external genitals in a male fetus, and warns women who may be pregnant not to handle crushed or broken tablets. Topical minoxidil is the approved option for female pattern hair loss, and the women’s foam label describes use once daily. The peptides for women page covers other female-specific labels.

What to look for on a hair serum label

Look past the front of the bottle to the ingredient list. These are the standard names: copper tripeptide-1, biotinoyl tripeptide-1 and acetyl tetrapeptide-3. Check whether the peptide is the only active or one of several, because almost every human result above comes from a mixture.

Then read the claims. FDA treats a product that claims to “restore hair growth” as a drug, which would need approval. That is why serums promise hair that looks fuller or stronger. A cosmetic that claims to regrow hair is being sold as an unapproved drug. If a serum says it works as well as minoxidil, ask to see a published trial.

If hair loss started on a GLP-1 drug

Hair shedding has been linked to the GLP-1 weight-loss drugs. A 2026 meta-analysis of nine interventional studies (4,114 users) found hair loss about 3.3 times more often than on placebo, in roughly 3.9% of users. A separate review pointed to rapid weight loss as a possible contributor. That is a conversation for the prescriber of the GLP-1 drug, and no reason to add an unapproved peptide.

What about injected peptides for hair?

We found no human hair trial of injected GHK-Cu, BPC-157 or TB-500 in a PubMed search on November 2, 2026. A September 2026 NPR report found no published human data showing injected GHK-Cu is safe or effective. As of November 2, 2026, HHS says it does not intend to take enforcement action against pharmacies compounding six named peptides under strict conditions. GHK-Cu is not one of them, none of the six is FDA-approved, and the policy says nothing about whether any of them grows hair. Vials sold for “research use only” are not legal to use on people.