Also: Long R3 IGF-1 · LR3IGF-I / Long Arg3 IGF-I · 'IGF', 'LR3', 'IGF-1 LR3'
RecoveryMetabolicInjection
Long-acting IGF-1 analogue (a cell-culture reagent) for muscle; hypoglycaemia, tumour-growth signal.
Safety tier
Avoid
strict bar
Positive
40%
of 24 reports
Per month
≈ €36–140
estimate
Rank
#54
of 61 research peptides
At a glance
Access
Grey market
Felt in 2–4 weeks
15 min1 h6 h1 day1 week1 month
Builds over days or weeks of regular use rather than with each dose.
Strict case
A potent, long-acting IGF-1 receptor agonist with no human data at all: it accelerated tumour growth in mice, the same receptor causes hypoglycaemic seizures and carries a malignancy warning on the approved IGF-1 drug, and every vial is grey-market.
Best effects
Big muscle pumps and fullness · faster recovery between sessions · quick strength gains (largely water in some reports) · lean-mass gain, mostly reported on top of steroids
Downsides
Hypoglycaemia (shaky, faint, 'felt like crap' when taken fasted) · water retention and puffy face in the first weeks · lethargy, tension headaches · severe next-day soreness in some · tolerance after 3-4 weeks, so it is cycled · expensive for what users get
Typical use
Community dosing is 20-100 mcg/day subQ or IM, usually after training with 0.5-1 g of fast carbs per mcg, for 4-8 weeks then the same time off. Never fasted. Users report 27–60 mcg/day (median 30 mcg, n=7).
Stacked with
Stacked with
Testosterone, anavar and other steroids: Most of the strongly positive reports come from people running it on top of a steroid cycle. · HGH or CJC-1295/ipamorelin: Often run alongside to offset feedback suppression of the user's own GH; many commenters say HGH alone is cheaper and better. · Retatrutide or tirzepatide: Added during or after a GLP-1 cut to hold muscle; users on both report hypoglycaemia crashes and sugar cravings. · PEG-MGF: An old forum protocol alternates weeks of LR3 and PEG-MGF; no data supports it.
Safety
Watch
Strong IGF-1 receptor activation that IGF-binding proteins barely hold back: accelerated tumour growth in a mouse cachexia model; theoretical promotion of existing or undiagnosed cancers · Hypoglycaemia, potentially severe: it is 2-3 times more potent than IGF-1 at lowering glucose in animals, and the approved IGF-1 drug causes hypoglycaemic seizures · Organ and soft-tissue growth seen with IGF-1 therapy (tonsils, spleen, kidneys, facial soft tissue) and with LR3 in rat gut · Never tested in humans; a His-tagged lab reagent has been found in a black-market vial
Tier by safety barStrict AvoidBalanced AvoidEvidence only Caution
Seen harm1 of 3
Mechanism3 of 3
Data gap3 of 3
Silent harm3 of 3
Product3 of 3
Never if
Active or past cancer, or a strong family history or known predisposition to cancer · Pregnancy or breastfeeding (no human reproductive data) · Children and teenagers with open growth plates · Diabetes, insulin or sulfonylurea use, or a history of hypoglycaemia · Use while fasting or before driving, as with the IGF-1 drug label
Split reports. Fans describe big pumps, fuller muscles, faster recovery and quick strength gains, often within 2-3 weeks. One user noticed less pain from a long-standing shoulder strain, and one 21-year-old says he gained weight and 2 cm of height. Most positive reports come from people also on testosterone, anavar, HGH or GLP-1s, so the effect cannot be separated out. Common downsides are water weight and puffiness, lethargy, tension headaches, intense soreness, light-headedness and hypoglycaemia symptoms when dosed without carbs; users keep dextrose or gummy bears to hand. There was one ER visit for a racing heart (normal ECG) and one report of a swollen prostate. At least one 17-year-old reports taking it, and younger teens keep asking about it. Felt nothing: About a fifth of first-hand reports felt nothing beyond a pump, and sceptics in every thread call it a waste next to growth hormone; a few blame degraded or fake vials, since it breaks down quickly once mixed..
So I started cycling it a little under a year ago. 6 weeks on 4-6 off. And lemme tell ya I’ve never had a more potent driver for just straight lean mass.
GlowingRecovery · about a year, 6 weeks on / 4-6 off
powerlifter on testosterone cypionate and EQ (about 750 mg/week) with arimidex; injects right after training with carbs and protein
Yeah I didn't notice anything ether just slightly a better pump
NothingRecovery
Studies
Evidence
Animal only — No human study of IGF-1 LR3. It was developed around 1990 in Adelaide, is sold mainly as a cell-culture reagent, and was tested only in rats, pigs and marmosets. The closest human data come from full-length IGF-1 (mecasermin, Increlex), which is a different molecule: shorter acting and held in check by binding proteins.
Caveat
No human pharmacokinetic or dosing data exist, so every community dose is extrapolated from cell-culture potency and bodybuilding forums. Reddit sentiment is heavily confounded by steroids and GLP-1s taken at the same time, and users report that LR3 barely moves a standard IGF-1 blood test, so they cannot check that a vial is active.
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.