PEG-MGF
Also known as Pegylated mechano growth factor, IGF-1Ec, MGF E peptide, PEGylated MGF
PEG-MGF is a pegylated copy of the E domain peptide of mechano growth factor, the IGF-1 splice variant muscle produces after loading or damage. In rodents and cell cultures it activates satellite cells and promotes repair. There are no human trials of any kind, and the pegylated version sold online has barely been studied even in animals.
Reviewed by the amino101 editorial team. .
Quick start
What people commonly do. Not a prescription.- Typical dose
- 200 to 400 mcg
- How often
- 2 to 3 times weekly on training days
- Where
- Subcutaneous, belly or near the trained muscle; some inject into the muscle itself, which adds risk without evidence
- Timing
- within 1 to 2 hours after training
- Effects timeline
- nothing to feel; any change in recovery or muscle is judged over 4 to 6 weeks and cannot be separated from training
- Storage
- fridge 2 to 8 C once mixed, use within 4 weeks; powder in freezer or fridge away from light
- Cycle length
- 4 to 6 weeks
- Break between
- 4 weeks
A 2 mg vial in 1 mL gives 2 mg per mL, so 200 mcg is 10 units and 400 mcg is 20 units on an insulin syringe.
Overview
Mechano growth factor is a splice variant of the IGF-1 gene, called IGF-1Ec in humans, that muscle fibers express for a short period after mechanical loading or injury. It differs from ordinary IGF-1 in its E domain, a tail of about two dozen amino acids that appears to act on its own to activate satellite cells, the stem cells that repair and grow muscle. Geoffrey Goldspink's group in London described it in the 1990s and showed that injecting the MGF gene into mouse muscle increased muscle mass. What research vendors sell as MGF is a synthetic copy of just the E domain peptide, not the full growth factor.
The human evidence is zero. No trial has given MGF or PEG-MGF to a person by any route. What exists is rodent and cell work: the E peptide drives myoblast proliferation in culture, MGF expression rises in human muscle biopsies after resistance exercise, gene delivery increases muscle mass in mice, and the peptide protects heart and brain tissue in rodent ischemia models. The pegylated version was created by vendors because the bare E peptide lasts only minutes in blood; attaching a polyethylene glycol chain is meant to stretch that to days. That claim comes from vendors, not from a published pharmacokinetic study.
Community protocols use 200 to 400 mcg subcutaneously or into trained muscle after a workout, two to three times a week, on the theory that MGF is the signal that recruits satellite cells in the hours after training. It is a Category 2 substance in the US as of 2023 and is prohibited by WADA under S2. This page is educational; it reports what the animal research and community use look like, and the honest summary is that nobody knows what this does in people.
How it works
After mechanical loading, muscle fibers briefly switch IGF-1 splicing to produce MGF instead of the usual systemic form. The MGF protein carries a different C-terminal E domain, and the E peptide on its own appears to signal through a receptor that is not the IGF-1 receptor, pushing satellite cells to proliferate while delaying their differentiation. This expands the pool of myoblasts available to fuse into damaged fibers. Expression then switches back to the standard IGF-1Ea form, which drives differentiation and protein synthesis. The synthetic E peptide is meant to reproduce the first step. Pegylation adds a polyethylene glycol chain to slow kidney clearance and protease breakdown, which should extend the time in circulation, though at the cost of some activity. Whether a circulating peptide reproduces what a locally expressed splice variant does inside the fiber is an open question.
Where the research stands
Muscle growth and repairWeak or mixed
- Hypertrophy. Gene delivery of MGF increased muscle mass in mice; no study has injected the peptide into a person or measured muscle outcomes.
- Satellite cell activation. The E peptide expands myoblasts in culture, which is the mechanistic basis for everything else and the only solid finding.
- Muscle injury recovery. Plausible from the biology of the natural splice variant; no animal or human study of injected peptide for injury.
Heart and brain protectionEmerging
- Ischemia protection. Rodent studies show the E peptide reduces damage in brain and heart ischemia models; purely preclinical.
Age related muscle lossWeak or mixed
- Sarcopenia. Older human muscle shows a blunted MGF response to exercise, which is a hypothesis for why injected MGF might help, not evidence that it does.
- rodentInjecting a plasmid encoding MGF into mouse muscle increased muscle fiber size and mass within weeks, more than the same delivery of standard IGF-1.
- in vitroThe synthetic MGF E peptide increased proliferation of cultured mouse myoblasts and delayed their differentiation, while mature IGF-1 did the opposite.
- human pilotMGF mRNA rose in human muscle biopsies within hours after a bout of heavy resistance exercise, with a blunted response in older men.
- rodentThe MGF E peptide reduced neuronal loss in a rodent model of brain ischemia and preserved cardiac function in animal models of myocardial infarction.
- in vitroNo published study has measured the pharmacokinetics or effects of a pegylated MGF peptide in any species.
Rodent and in vitro mean no human data for that finding. Human pilot means small, often uncontrolled. Human RCT means randomized and controlled. Clinical means an approved drug with regulatory data.
Levels over time
Modeled from the half-life. Illustrative, not measured.A half-life of 2 d against dosing every 7 d means each dose has cleared before the next. Nothing stacks; you start from zero every time, and the tissue effect is what carries over.
The number here is the vendor claim, included so the field is not blank. No pharmacokinetic study of PEG-MGF exists in any species, and the natural E peptide disappears from blood within minutes.
PEG-MGF dosage and protocols
Community runs are 4 to 6 weeks of two to three injections a week on training days, then a month off. Some protocols alternate PEG-MGF weeks with IGF-1 LR3 weeks to mimic the proliferation then differentiation sequence seen in rodent muscle. None of this has been tested, and there is no basis for choosing one length over another beyond habit.
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Standard post-training protocol, community | 200 mcg | 3 times weekly after training | Subcutaneous, abdomen or near trained muscle |
| Higher end | 400 mcg | 2 times weekly after the hardest sessions | Subcutaneous or intramuscular |
| Bilateral split, community | 200 mcg per side | 2 times weekly after training | Intramuscular, split between the trained muscles |
| Alternating with IGF-1 LR3 | 200 to 300 mcg | 2 to 3 times weekly, on weeks without IGF-1 LR3 | Subcutaneous |
The post-training window is the whole rationale: natural MGF expression peaks in the hours after loading, so people inject within an hour or two of finishing. Food does not matter. Because the pegylated form is claimed to last days, the exact timing probably matters less than the community assumes, if it matters at all.
Community protocols report 200 to 400 mcg per injection, two to three times weekly, usually after training. No human or animal dosing study supports these numbers.
Dose calculator
U-100 insulin syringeUnits are a volume on the syringe, not an amount of peptide. Concentration changes every time you change the water volume. The standalone calculator explains the math.
| Vial | Suggested water | Concentration | Low dose draw |
|---|---|---|---|
| 2 mg | 1 mL | 2 mg/mL | 10 units |
| 5 mg | 2 mL | 2.5 mg/mL | 8 units |
How to reconstitute PEG-MGF
- 1
Wash your hands and wipe the work surface. Swab both vial stoppers with alcohol and let them dry.
- 2
Pick the water volume with the calculator above and write it on the vial. The concentration means nothing without it.
- 3
Draw the bacteriostatic water into a mixing syringe.
- 4
Insert at an angle and let the water run down the inside wall. Never squirt it straight onto the powder.
- 5
Swirl gently or leave it to dissolve. Do not shake.
- 6
Label with the date and water volume. Store in the fridge at 2 to 8 C and use within about 4 weeks.
- 7
Unmixed vials keep for months in the fridge and longer in the freezer, sealed and out of light.
- Full walkthrough with syringe reading and site rotation: reconstitution guide.
- ✓White, fluffy cake
Lyophilized powder should look like a small white puck or fluffy cake at the bottom of the vial. That is a proper freeze-dry.
- ✓Clear after mixing
Once dissolved the solution should be water-clear with nothing floating in it.
- !Slight clumping
Small clumps that dissolve with gentle swirling are fine. Shipping compacts powder.
- ✕Collapsed or melted
Powder stuck to the sides, glassy, or shrunken means it got hot in transit. Contact the vendor.
- ✕Cloudy or particles
Persistent cloudiness or visible particles after mixing means degraded or contaminated product. Do not use it.
- Week 1 to 2
Nothing to feel beyond injection site soreness, especially with intramuscular injection; some people report a pump or fullness in the trained muscle that is probably the injection volume and the training.
- Week 3 to 6
Any recovery or size change is judged here, and it cannot be separated from training, food and other compounds; there is no measurable marker to track.
- After the cycle
Whatever was gained is kept or lost on the merits of the training, since no evidence shows the peptide added anything.
Interactions and stacking
IGF-1 LR3compatible
The classic pairing, run on alternating days or weeks to mimic the proliferation then differentiation sequence; untested and stacking two IGF family compounds compounds the growth concern.
Ipamorelincompatible
Growth hormone secretagogues raise systemic IGF-1 and are often run alongside; no known interaction.
CJC-1295 (no DAC)compatible
Same reasoning as ipamorelin; no data on the combination.
BPC-157compatible
Used together in muscle injury protocols; no known interaction.
HGHcaution
Adding a growth factor on top of exogenous growth hormone stacks proliferative signals with no safety data.
Insulincaution
IGF family peptides can lower blood glucose; the effect of the E peptide on glucose is unknown, so anyone using insulin should be careful.
Active cancer or cancer historyavoid
A peptide whose job is to make cells proliferate has no place alongside a cancer diagnosis.
The classic community pairing, with PEG-MGF after training to expand satellite cells and IGF-1 LR3 on other days or later to drive differentiation. It mirrors the rodent splicing sequence and has never been tested.
Growth hormone secretagogues are often run under a PEG-MGF cycle to raise systemic IGF-1; no known interaction and no data on the combination.
Used together in injury protocols aimed at muscle tears, with BPC-157 for tendon and tissue repair; purely a community combination.
Safety
- ▲Injection site soreness, bruising or swelling, more so with intramuscular injection
- ▲Transient lightheadedness after a dose
- ▲Mild hypoglycemia symptoms have been reported anecdotally, unverified
- ▲Joint aches when stacked with IGF-1 LR3 or secretagogues
- ▲Infection or nerve irritation from repeated intramuscular injections
- ▲No human data of any kind. Not one trial, not one pharmacokinetic study, not one case series. Everything is extrapolated from mice and cell cultures.
- ▲The pegylated form is a vendor invention. Pegylation can change how a peptide behaves and no study has characterized PEG-MGF in any animal.
- ▲Driving cell proliferation is a theoretical cancer concern, as with anything in the IGF family. No safety data either way.
- ▲Prohibited in sport by WADA under S2 as a growth factor.
- ▲In 2023 the FDA placed MGF in Category 2, so it cannot be compounded in the US.
- ▲Injection into muscle carries infection and nerve injury risk; intramuscular use is a community practice with no evidence that local injection does anything a subcutaneous dose would not.
- ■A new lump, mass or unexplained growth anywhere
- ■Signs of infection at an injection site such as spreading redness, heat or pus
- ■Numbness, tingling or weakness after an intramuscular injection
- ■Signs of an allergic reaction such as hives, swelling or trouble breathing
- ■Symptoms of low blood sugar such as shaking, sweating or confusion
Community poll
Self-reported by visitors. Not clinical evidence.PEG-MGF: frequently asked
What PEG-MGF dosage is reported?
Community protocols report 200 to 400 mcg per injection, two to three times a week after training, for 4 to 6 weeks. These figures come from forums and vendors. There is no human or animal dosing study of PEG-MGF, so no dosage has been shown to do anything, and the numbers should be read as what people use rather than what works.
Does PEG-MGF build muscle?
In mice, delivering the MGF gene into muscle increased fiber size, and the E peptide expands myoblasts in culture. In people there is no evidence at all. The body already makes MGF after every hard training session, and whether adding a circulating pegylated copy changes anything is unknown. Community reports are mixed and heavily confounded by the training and other compounds people run alongside it.
Why is it pegylated?
The natural E peptide is cleared from blood in minutes, which makes it useless to inject. Attaching polyethylene glycol slows clearance and protease breakdown, and vendors claim this extends the half-life to days. That claim has not been tested in a published study, and pegylation can also reduce a peptide's activity, so the trade off is unknown.
Should it be injected into the muscle that was trained?
People do this on the theory that MGF acts locally, which is how the natural splice variant works. But a pegylated peptide injected into muscle still diffuses into the bloodstream, and there is no evidence that local injection produces local growth. Intramuscular injection adds risk without demonstrated benefit.
References
- Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation. FEBS Letters, 2002
- Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise. Journal of Physiology, 2003
- Mechano growth factor: a novel splice variant of IGF-1 with roles in muscle, heart and brain. Physiological Reviews and related reviews by Goldspink, 2005
- A strong neuroprotective effect of the autonomous C-terminal peptide of IGF-1 Ec (MGF) in brain ischemia. FASEB Journal, 2005