PEG-MGF
Also called mechano growth factor, IGF-1Ec
MGF stands for Mechano Growth Factor: a variant of IGF-1 that your muscle makes itself in response to damage.
The published research here is animal and laboratory work. The ranges below come from community-reported dosing and results — what people have settled on in practice, and what they report happening.
- Body composition
- Recovery & injury
The quick answer
MGF stands for Mechano Growth Factor: a variant of IGF-1 that your muscle makes itself in response to damage. It is the local signal that says this fibre tore, send satellite cells. The PEG version has a polymer attached to stop it disappearing within minutes.
What it is not
Not a systemic growth compound and not interchangeable with IGF-1 LR3.
Why people use it
🎯 A local repair signal rather than a systemic growth one; 🩹 Recovery is the main reported effect; 💪 Used after hard training rather than continuously; 🍬 None of the blood-sugar trouble that comes with IGF-1 LR3
What people report using
These are ranges other people have reported running. They are here so you can see what has actually been done — they are not medical advice and not a recommendation for you.
- How often
- Post-workout, 2–4 times a week
- Route
- subcutaneous
- Evidence for this
- Animal and lab research
Fullness or soreness in the trained area.
What to expect, and when
In the days after a hard session: reduced soreness. Nothing is described in weeks or months the way the GH-family compounds are.
Side effects, and what people do about them
Little reported beyond injection-site reactions. It does not carry the low-blood-sugar problem that dominates IGF-1 LR3 discussion, which is the main practical reason people choose it.
Go deeper
Open these only if you want them.
How it actually works
A splice variant of IGF-1 with a distinct C-terminal E-domain peptide, which is the active fragment here. It acts locally to activate satellite cells rather than systemically the way IGF-1 LR3 does. Natural MGF has a half-life measured in minutes; PEGylation stretches that to hours, which is the only reason an injectable version is practical at all.
More on the evidence
Rodent work only. No human trial of the pegylated form.
The case against
Animal and cell work only. The muscle biology behind MGF is well established; whether injecting a PEGylated version reproduces that local signal in humans has not been shown.
What people report, in full
PEG-MGF has a specific and consistent place in community practice: after training, not before, and not daily. The reasoning people give is that it is a repair signal, so it belongs where repair happens. Recovery is what they describe - less soreness, feeling ready sooner - rather than growth in any direct sense, and experienced users are usually the ones correcting newer ones on that point. It is often framed as the gentler alternative to IGF-1 LR3, and the specific reason given is blood sugar: people who found LR3 unpleasant to live with moved here. The other recurring theme is honest scepticism about whether an injected version really reaches the tissue that matters - a fair question the community raises on itself.
Sources and review
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2342958
https://pubmed.ncbi.nlm.nih.gov/21354439/
Last reviewed 2026-09-08.
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