Also: MGF: synthetic 24-amino-acid E-domain peptide of the IGF-1Ec splice variant (IGF-1Eb in rodents) · PEG-MGF: the same peptide attached to polyethylene glycol to make it last longer · pegylated mechano growth factor · '3x blend MGF' (vendor blends)
ExcludedInjection / Nasal
IGF-1 splice-variant peptide (plain or PEGylated) for muscle repair; disputed biology, cancer-cell signal.
#28 of 61 research peptides · updated
Onset
Users report less soreness from the first sessions; injury reports talk of weeks.
Lasts
Plain MGF is described as lasting minutes, so it is injected straight after training; PEG-MGF is dosed every 2-3 days.
I did a cycle of PEG-MGF with BPC + TB 10mg from a sports injured. Was inspired by the "research" and presentation from Hunter Williams making some solids arguments about the synergies with all 3 compounds. It's all of course subjective and anecdotal but I felt I got over my injury faster then expected.
Positiveone cycle
PEG-MGF stacked with BPC-157 and TB-500, so the effect cannot be attributed
The injection hurts like hell. I didn't get any benefit but I may not have been running enough.
Nothing
later summed it up as 'it does nothing'
Strict case
An unapproved growth-factor fragment with no human dosing data at all. The peptide drove prostate-cancer cell growth and metastasis in mice by a route that bypasses the IGF-1 receptor, and the pegylated form people buy has never been characterised.
Users report
Very few first-hand reports exist; most threads are people asking whether anyone has tried it. The two positive reports are about recovery, not growth: one used plain MGF in the biceps after training and could train arms to failure daily without soreness, the other ran PEG-MGF with BPC-157 and TB-500 for a sports injury. Others got nothing but a painful injection. Bodybuilders say it has circulated for over a decade without catching on, and the YouTuber Vigorous Steve is cited as calling the products junk. One intranasal user felt warm and sweaty after the first dose and never reported back. Felt nothing: Too few reports to judge. Of the handful of users, one felt nothing but a painful injection; long-time bodybuilders say most people get nothing from it..
Best effects
Faster recovery and less soreness after training (anecdotal) · faster injury healing, usually alongside BPC-157/TB-500
Downsides
Painful intramuscular injections · no felt effect for many · plain MGF has to be injected right after each session; PEG-MGF 2-3 times a week
Watch
Growth-factor-like signalling: the MGF E peptide drove prostate-cancer cell growth in vitro and tumour growth and metastasis in mice, independently of the IGF-1 receptor; theoretical promotion of existing cancers · PEG-MGF is an uncharacterised pegylated conjugate: its exposure, clearance and immunogenicity in people are unknown · Disputed biology: a two-company replication found the peptide inactive on muscle stem cells, so a vial may be inert or contain something else · No human data; grey-market injectable
Evidence
Animal only — No human has been given MGF or PEG-MGF in any published study. The human evidence is about the body's own MGF: muscle biopsies show its mRNA rises after resistance exercise in young but not older men. The rest is cell and mouse work, and its key claim (muscle stem-cell activation) failed independent replication in 2014.
Caveat
MGF and PEG-MGF differ mainly in how long they last. Plain MGF is the short synthetic E-domain peptide, injected into the trained muscle within about 30 minutes of a session. PEG-MGF carries a polyethylene glycol chain meant to extend that to days, and is injected subQ or IM a few times a week. Neither has human pharmacokinetic data, and the 2014 failed replication means it is unclear whether either does anything; reported benefits may be placebo or the other compounds they are stacked with.
Typical use
No clinical dose exists. Plain MGF: about 100-200 mcg per muscle straight after training. PEG-MGF: 200-400 mcg 2-3 times a week.
Getting it
Research-peptide vials only. MGF was nominated for US 503A compounding but is not on the list. Both forms are banned in sport by WADA (S2, 'mechano growth factors').
Stacked with
BPC-157 and TB-500: Used together for injuries; the one positive PEG-MGF injury report is for this trio, so MGF's share cannot be told apart. · IGF-1 LR3 or IGF-1 DES: Old forum protocols alternate LR3 weeks with PEG-MGF weeks, or pair MGF with DES on the same day, on the theory that LR3 blunts MGF; none of this has been tested. · HGH or CJC-1295/ipamorelin: Users ask whether raised IGF-1 from GH cancels MGF; nobody knows.
I did a cycle of PEG-MGF with BPC + TB 10mg from a sports injured. Was inspired by the "research" and presentation from Hunter Williams making some solids arguments about the synergies with all 3 compounds. It's all of course subjective and anecdotal but I felt I got over my injury faster then expected.
Positiveone cycle
PEG-MGF stacked with BPC-157 and TB-500, so the effect cannot be attributed
While user content is limited, research supports its benefits and safety in controlled use. For those curious, combining PEG-MGF with proper training and nutrition yields the best outcomes. This post is for research and educational purposes only.
Glowingvendor-adjacent
promotional summary that asserts proven safety and ends with the 'for research and educational purposes only' disclaimer vendors use
Safety
Tier by safety barStrict ExcludedBalanced ExcludedEvidence only Caution
Seen harmMechanismData gapSilent harmProduct
Seen harm 0/3
No case report, trial or regulator warning involves MGF or PEG-MGF, and the few first-hand Reddit reports describe only injection pain and, in one intranasal user, sweating. The zero reflects almost no documented human exposure, not reassurance; the gap is carried by dataGap. r/BodyHackGuide: Experience with PEG-MGF ↗
Active or past cancer, especially prostate cancer, or a known predisposition to cancer · Pregnancy or breastfeeding (no human reproductive data) · Children and teenagers · Known allergy to polyethylene glycol (PEG-MGF)
Each bead is one amino acid in the peptide's chain, coloured by its side chain: grey for non-polar, cyan for polar, blue for positively charged and fuchsia for negatively charged. Length and mix tell related peptides apart at a glance, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4. The colours describe chemistry only and predict neither effect nor safety.
non-polarpolarpositivenegative
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. Kept peptides rank by the same reports' mean grade, shrunk the same way, and excluded ones follow in that order.
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 alongside the computed scores until reports arrive.
Safety tier
Each peptide is tiered clean, caution or excluded from its five risk axes under the chosen safety bar. An excluded peptide has a plausible route to serious harm, 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 exclude a peptide. 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.
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.
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.