Zinc-bound thymic nonapeptide; injected for immunity, sprayed on scalps for hair. 1980s data only.
Safety tier
Caution
strict bar
Positive
49%
of 4 reports
Per month
Not priced
Rank
#15
of 61 research peptides
At a glance
Onset
Nothing felt acutely; immune effects are judged over weeks to months, and scalp regrowth in the topical series showed at about 6 months
Lasts
Cumulative; users run short injection courses once or twice a year, while the topical is applied daily and indefinitely
Access
Grey market
Best effects
Fewer infections or herpes outbreaks (anecdotal, stacked) · less brain fog in CIRS (anecdotal, stacked) · new vellus and intermediate scalp hairs (one small open-label topical series)
Downsides
Daily injections in the only controlled trials (1-10 mg/day subq) · cost of compounded scalp foams and serums · no felt effect to confirm it is working
Typical use
No established dose. The rheumatoid-arthritis trials used 1-10 mg/day subq (5 mg best), daily for two weeks and then three times a week; grey-market courses are improvised. Topical: daily scalp spray or foam.
Stacked with
Stacked with
Thymalin and thymosin alpha-1: Run together as 'thymic peptides' by HSV and CIRS users, which makes thymulin's own effect impossible to separate. · Vilon, VIP, KPV: Part of CIRS protocols, with thymulin and Vilon as the short 'immune gene regulator' course. · GHK-Cu (topical): The usual commercial scalp pairing, sometimes with PTD-DBM, alongside or instead of minoxidil.
Safety
Watch
Theoretical: an immunomodulator in people with autoimmune disease or lymphoid cancer (one Reddit user with CLL was about to inject it); the 1980s rheumatoid-arthritis trials saw no flares, but the data are thin · Grey-market vials are mostly the zinc-free nonapeptide, which is inactive unless zinc binds it, and identity, sterility and endotoxin are unverified · Name confusion with Thymalin (Russian calf-thymus extract) means people may not get the molecule they think they bought
Tier by safety barStrict CautionBalanced CleanEvidence only Clean
Seen harm0 of 3
Mechanism1 of 3
Data gap2 of 3
Silent harm1 of 3
Product3 of 3
Never if
Pregnancy or breastfeeding (no human reproductive data) · Organ transplant or other immunosuppressive therapy · Lymphoid cancers such as CLL or lymphoma, where T-cell stimulation is untested
Small human studies only: two 1980s rheumatoid-arthritis RCTs and case reports from one Paris group, and one uncontrolled 18-person topical series. No approval anywhere and nothing modern. The trials used synthetic zinc-thymulin, the same molecule sold today, though most vials are sold zinc-free. Amor et al. 1987 (PubMed) ↗Superpower peptide guide: thymulin (no modern interventional trials) ↗
Silent harm 1/3
The harms most plausible for what people actually inject are injection-site and contamination reactions and a flu-like flare, all noticed within days. A slower immune effect, such as an autoimmune flare, would mostly show as symptoms but could take weeks to appear. Mendias & Awan 2026 preprint: grey-market peptide quality failures and endotoxin ↗
Too few reports to judge: four first-hand accounts, three of them on multi-peptide or multi-drug stacks. Two injectors credit it. One HSV-2 user had no symptoms for over a year on a Thymalin, thymulin and TA-1 course, though a prodrome came back months later. One CIRS user had less brain fog for a year after a thymulin and Vilon course and wonders if it was placebo. A second CIRS patient two weeks into prescribed injections could not tell whether anything had changed. A hair-loss user who ran a GHK-Cu/zinc-thymulin topical for a year among several treatments cannot say it did anything. Users also mix it up with Thymalin: one HSV user's vial labelled 'Thymalin' turned out to be thymulin. Felt nothing: 2 of 4 reports; too few reports to judge.
Since using thymic/immune peptides (from a reputable supplier) - specifically Thymalin, Thymulin, and TA-1 -- I have absolutely nothing, not even the tiniest symptom, for more than a year.
Positiveabout a year of experimenting with thymic peptides
HSV-2; stacked with Thymalin and TA-1; says her vial labelled 'Thymalin' was actually the thymulin nonapeptide
Anecdotally they have had long lasting benefits as I did a course 1 year ago and I’ve had less brain fog since, but I don’t know how much of it is placebo or in general and increase in my health as a whole because there are so many other factors.
PositiveInjection · one course a year earlier
CIRS; thymulin and Vilon as one course inside an eight-peptide stack (VIP, TA-1, KPV, LL-37, BPC-157)
Was super expensive and I dont remember if they worked or not. Cost me about 1K per month. Topical Dutasteride worked for sure but unsure about the rest
NothingSkin & hair · Topical · about a year (2019)
Androgenetic alopecia; GHK-Cu with Zn-thymulin topical alongside topical dutasteride/latanoprost, TB-4 injections and PTD-DBM/valproic acid; credits only the dutasteride
Studies
Evidence
Small human studies — Two small double-blind rheumatoid-arthritis trials and immunodeficiency case reports from the Bach/Dardenne group in the 1980s, plus one uncontrolled 18-person topical hair series (2017); nothing modern, no approval anywhere
Caveat
Almost everything known about thymulin as a drug comes from one Paris group in the 1980s; the topical hair claim rests on a single uncontrolled series and organ-culture work. The molecule needs zinc bound to be active, and most research vials are sold zinc-free, so what people inject may do nothing. Thymuskin's Reddit reports (some regrowth, some shedding and red scalp) are about a thymus-extract product and are not counted here.
Prasad et al., Serum thymulin in human zinc deficiency (J Clin Invest 1988)observational · n=14 · 1988 Thymulin activity in blood depends on zinc: it fell in mildly zinc-deficient adults (two induced by diet, twelve with existing deficiency) and recovered with zinc repletion, along with their T-cell subsets and IL-2.
The peptide's chain of amino acids from its start (the N-terminus) to its end, one bead and one letter for each: A alanine, C cysteine, D aspartic acid, E glutamic acid, F phenylalanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine. A modification such as an N-acetyl cap or a C-terminal amide changes how long it lasts in the body. Length tells related peptides apart, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4, and predicts neither effect nor safety.
Report grades
Every first-hand Reddit or X report is graded on its own, from glowing through positive, mixed, nothing and negative to bad reaction, and the bar shows how those grades split. Posts that look vendor-adjacent stay on the peptide's page but are left out of the counts.
GlowingPositiveMixedNothingNegativeBad reaction
% positive
The share of a peptide's graded Reddit and X reports that are glowing or positive, vendor-adjacent posts left out. A peptide with few reports is pulled toward the average of all reports, as if it had eight average ones besides its own, so two glowing posts cannot top the list. Peptides rank by this figure, those with no graded report yet after those with one, and Avoid ones after every other entry.
Researcher estimate
No first-hand report of this peptide has been graded yet, so the figure is the researchers' own rating out of 10 from what they read about it. It ranks after every peptide with graded reports until its own arrive.
Safety tier
Each peptide is tiered Clean, Caution or Avoid from its five risk axes under the chosen safety bar. An Avoid peptide carries a real risk of harm, a plausible route to serious harm rather than mere unpleasantness, so it stays listed with the reason but ranks behind every other entry, however good its reviews.
Safety bar
The safety bar sets how much risk it takes to rate a peptide Avoid. Strict: out on any serious mechanism with little human data, or any documented serious harm. Balanced: out on documented serious harm (unless it is obvious, reversible and from a regulated product), or a serious mechanism whose harm would be silent with no human data at all. Evidence only: out only on documented serious harm in humans that is lasting, delayed or from grey-market product.
Seen harm
Documented serious adverse events in humans, from 0 for none despite real exposure to 3 for deaths or several well-documented serious harms. Serious means a hospital or emergency visit or harm lasting weeks, so a headache or a bad night does not count.
Mechanism
A plausible biological route to serious harm at the doses people use, such as growth-factor signalling, hormone-axis suppression, heart or blood-pressure effects or immune activation. It runs from 0 when none is known to 3 when a dangerous pathway has been shown in living animals.
Data gap
How little human safety data exists for the molecule actually sold, from 0 for an approved drug with large trials and years of use to 3 for no human safety data at all. A modified analogue does not inherit its parent's trials.
Silent harm
Whether the feared harm would show quickly or stay hidden, from 0 when it is obvious and goes on stopping to 3 when it is silent and delayed, like tumour promotion or slow organ damage. User reports cannot reveal a harm that takes years to appear, so a high score here limits what good reviews can tell you.
Product
The risk of what people actually buy, from 0 for a regulated pharmacy or supplement product taken by mouth or on the skin to 3 for a grey-market injectable. In one dataset of 6,441 grey-market samples, 42–71% failed basic quality criteria and 15% carried endotoxin; taken by mouth or in the nose, a pack avoids the injection risks.
Evidence
The strongest kind of study behind the peptide's effects, from an approved drug through human controlled trials and small human studies to animal work or nothing of its own. Animal results often fail to carry over to people.
Access
How people get it: as an approved drug, a compounded prescription, an over-the-counter supplement or from the grey market, where nobody checks the vial. The channel decides both the legal position and the risk of a bad batch.
Price per month
Thirty days of the typical dose, from its low end to its high end, priced at the listing a careful buyer would choose: in stock, from a shop scoring 4 of 5 on trust (third-party tested where no score is set), failing that 3, a pure pack before a blend, a European shop first, then the cheapest per mg. The range is the dose's, not the shops'. A per-dose amount counts once a day unless the dose says otherwise. Prices are in euros at ECB rates of 2026-10-29, before shipping; the shop table keeps each listing's price per mg, per gram for bulk supplements. Where no listing can be priced the researchers' own estimate stands in, and says so.
Dose users report
The middle half of the daily doses stated in at least five first-hand reports, vendor posts left out. Where its middle sits more than twice above or below the declared dose, the month is priced at it as well, since what people take is what they pay for.
Shop trust
Each shop's trust on a 1–5 scale, read from its testing and its reputation: 1 for serious red flags (fabricated COAs, scam reports, impersonation, a closed shop), 2 for no public testing, a new shop or active complaints such as seized parcels, 3 for its own COAs or a short track record, 4 for verified third-party testing or a strong reputation, and 5 for third-party batch reports that name the shop, with years of good independent reputation. A shop without a score counts third-party batch testing as 4, its own COAs as 3 and no public tests as 2.
Best value
Within a category or a goal, a peptide that no other beats on both counts: none is rated more positively for the same or a lower monthly price, and none costs less for the same or a higher rating. The chart joins these into the best-value line; the cheapest of them and the best-rated of them both make it, so the line spans the trade-off from cheap to best. Avoid entries never count, and a peptide needs both a % positive and a price to be compared.
Testing
Whether the shop publishes lab results: third-party tested means an independent lab checks each batch, own COA means the shop's own certificate of analysis, and no public tests means neither. A certificate shows purity, not safety.
Added peptide
Some packs sold under one peptide's name hold a second one, such as 5 mg GHK-Cu in a nasal kit, stated only in the description. Sprayed in the nose or injected it reaches the blood like an injection, so it carries the risk of that route and is tiered as the injectable form, whatever its tier on the skin. A pack whose page gives no contents list may hold more than its name.