PepRank

LL-37

Also: cathelicidin · hCAP-18 C-terminal peptide · CAP-18

GutRecoveryTopical / Injection

Endogenous antimicrobial peptide for chronic infections/dysbiosis; pro-inflammatory, pro-tumour in places.

Safety tier
Avoid
strict bar
Positive
53%
of 26 reports
Per month
≈ €45–110
estimate
Rank
#30
of 61 research peptides

At a glance

Access
Grey market
Felt in 7 days – 5 weeks

Builds over days or weeks of regular use rather than with each dose.

Strict case
Pro-inflammatory/autoimmune and context-dependent pro-tumour activity, plus FDA-noted reproductive effects.
Best effects
Clearing stubborn infections (anecdotal) · biofilm/dysbiosis claims · wound healing (topical)
Downsides
Brain fog, malaise · Herxheimer-type flu-like reactions · injection-site inflammation
Typical use
100-250 mcg/day subQ in short courses.
Stacked with
Stacked with
Thymosin alpha-1: The usual partner in Lyme and mould protocols, taken to support immunity while LL-37 is the antimicrobial; also what users credit for some of the die-off. · BPC-157 and KPV: Gut stacks for SIBO, H. pylori and candida; users who improved on these stacks cannot separate the peptides. · Binders (charcoal, zeolite, cholestyramine): Taken to blunt die-off reactions, alongside a lower starting dose.

Safety

Watch
Pro-tumorigenic in ovarian, breast and lung cancer models (FDA note) · Drives autoimmune inflammation (psoriasis, lupus) and is found in atherosclerotic plaque · FDA: nonclinical detrimental effects on male reproduction
Tier by safety barStrict AvoidBalanced CautionEvidence only Caution
  • Seen harm1 of 3
  • Mechanism2 of 3
  • Data gap3 of 3
  • Silent harm2 of 3
  • Product3 of 3
Never if
Psoriasis, lupus or other autoimmune disease · Active cancer or a history of cancer · Trying to conceive (male reproductive effects in animals) · Pregnancy or breastfeeding (no human reproductive data)
Why each score
Seen harm 1/3
Of the three people ever injected with it in a trial, one developed a keratoacanthoma-like skin proliferation that cleared after stopping; topical trials saw more local reactions at the highest dose, and one first-hand report describes a face swollen shut for a week. Isolated. Dermatologic toxicity from intratumoral LL-37 in melanoma: keratoacanthoma-like proliferation (PubMed 29665030) ↗Grönberg et al. 2014: topical LL-37 in venous leg ulcers, phase 1/2, n=34 (PubMed 25041740) ↗r/Biohacking: face swollen shut for a week after two low doses of LL-37 ↗
Mechanism 2/3
Immune activation that is established in humans: LL-37 is a T-cell autoantigen in nearly half of psoriasis patients and helps drive lupus by delivering self-DNA to dendritic cells. Pro-tumour data come only from blocking or knocking out the endogenous peptide, and FDA notes male reproductive effects in animals. Lande et al. 2014: LL-37 is a T-cell autoantigen in psoriasis (Nat Commun) ↗LL-37 in lupus: self-DNA delivery to plasmacytoid dendritic cells and anti-LL-37 autoantibodies ↗FDA: bulk drug substances that may present significant safety risks (category 2 and withdrawn nominations) ↗
Data gap 3/3
Topical trials cover about 180 people, but there is no human safety data for the subcutaneous injection people use beyond three intratumoral melanoma patients. Grönberg et al. 2014: topical LL-37 in venous leg ulcers, phase 1/2, n=34 (PubMed 25041740) ↗HEAL phase IIb: topical LL-37 in venous leg ulcers, about 148 randomised, failed primary endpoint ↗Dermatologic toxicity from intratumoral LL-37 in melanoma: keratoacanthoma-like proliferation (PubMed 29665030) ↗
Silent harm 2/3
Autoimmune disease would build up over weeks to months, though its skin, joint and blood signs are detectable. Lande et al. 2014: LL-37 is a T-cell autoantigen in psoriasis (Nat Commun) ↗
Product 3/3
Grey-market injectable vials only; it is on FDA's risk list, so US pharmacies cannot compound it. FDA: bulk drug substances that may present significant safety risks (category 2 and withdrawn nominations) ↗Mendias & Awan 2026 preprint: 6,441 grey-market peptide samples, 42-71% failed quality criteria, 15% had endotoxin ↗

User reports

All 27 reports →
Users report
There are few reports. Some credit it with clearing long-running low-grade infections or cellulitis alongside antibiotics, or with dysbiosis. Others feel 'off' with worst-ever brain fog or Herxheimer-type reactions, and many keep it only for acute illness because of the risks discussed.
Glowing 4Positive 10Mixed 4Nothing 2Negative 4Bad reaction 2
  • r/Peptidesource· · 2 upvotesOriginal ↗

    Antibiotics were working, introduce the LL-37 and within 3 weeks the infection cleared. I used it on half dose to avoid a bad flu that was going round but it cleared up my athletes foot like no other cream before, 3 months in and I'm still all clear

    GlowingInjection

    own athlete's foot, plus a relative's cellulitis foot infection already on antibiotics; half dose

  • r/SIBO· · 2 upvotesOriginal ↗

    Killed all the nad crap. Was a rough ride for 5 weeks. Tongue got pink again, no more bloating and all the other crap that comes with h pylori , sibo and candida

    GlowingGut · Injection · 5 weeks

    H. pylori, SIBO, candida and mould exposure; stacked with BPC-157

  • r/SIBO· · 3 upvotesOriginal ↗

    I have tried all 3, oral and injected BPC157 and noticed no difference from any of them on gut symptoms.

    NothingGut

    SIBO gut symptoms; also tried KPV and BPC-157

Where to buy

All 6 offers →
Getting it
Research-peptide vendors only; on the FDA's Category 2 list, so US pharmacies cannot compound it, and users report it getting harder to find. No approved product anywhere.

No listing can be priced, so the researchers estimate ≈ €45–110 a month.

No trusted shop in the EU lists it; every listing is on the buy page.

Studies

Evidence
Small human studies — Topical phase 2 for venous leg ulcers; injectable use animal only
3 more studies and 2 sources

Sources

Molecule

Sequence
LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES
Length
37 amino acids
Modifications
unmodified (cathelicidin, CAMP C-terminus)

Sequence

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.