MGF dosage and evidence

What is MGF?

How does MGF work?

Proposed activation of muscle satellite cell proliferation through a receptor distinct from IGF-1R.

What have studies in people found about MGF?

No person has been given lab-made MGF in any published study. The only human data anywhere near it measured the body's own MGF signal in muscle samples after heavy exercise, in 15 men, and gave nothing to anyone. Scientists also disagree about whether the peptide being sold matches anything the body actually makes.

• Human muscle, not human dosing: 8 men aged 25 to 36 and 7 men aged 70 to 82 did 10 sets of 6 one-leg knee extensions at 80 percent of the most they could lift once. Thigh muscle samples were taken from both the worked leg and the rested leg 2.5 hours later. The gene message for MGF rose clearly in the young men and not in the older men. A related IGF-1 gene message did not change in either group. At rest, MGF was about 100 times lower than the related form. This is the study quoted as human evidence for injecting MGF, and it involves no injection.
• No studies giving it to people. No published paper gives lab-made MGF, or its short end piece, to a person by any route.
• No registered trials. A ClinicalTrials.gov search finds only IGF-1 and growth hormone studies, which are different drugs.
• The dispute over what it is, stated by scientists with nothing to sell: a 2010 review in Endocrinology reports that the gene message is real and rises after muscles are loaded. But no matching peptide has ever been found in cells grown in a lab, the fluid around them, animal tissue or any body fluid.
• How long it lasts: the natural peptide is cleared in minutes, which is the stated reason the PEG version exists. Nobody has published how long either form lasts in a person.
• In a dish, human cells: the MGF end piece made human muscle stem cells, from people of different ages, multiply more and fuse better. Cells from people, not people.
• In a dish, pig cells: MGF made pig muscle stem cells multiply, and held back the switches that turn them into mature muscle. So it delayed muscle building rather than driving growth.

What this does not tell you: Nothing is known about what injecting this peptide does to a person, at any dose, by any route, over any length of time. The exercise study describes a gene switching on in muscle, and cannot tell you what a peptide from outside the body does. The lab work shows cells multiplying in a dish, which is a long way from a bigger muscle. In the pig cell work, the cells divided but did not mature. Claims about injecting it into one target muscle have never been tested in any species with a measured result.

What do people who took MGF report?

This is what real people say happened to them, good and bad. Nobody measured it. A report cannot tell a real effect from the lift people get just from expecting it to work, from a diet or training change made at the same time, or from what was really in the vial. We still put it near the top. It is the next best thing to a study in people: what happens when real people use it, including what goes wrong.

• Discussion is old and comparatively thin, and what exists skews negative, which is unusual in this setting and worth noting for that reason alone.
• Described use is in one spot rather than through the whole body: roughly 100 to 200 mcg injected into one muscle, usually immediately after training that muscle, with the stated aim of size in that specific place.
• What people describe seeing is short lived swelling and fullness rather than lasting change, and the most repeated observation is that whatever appeared went away after stopping. Several attribute the visible difference to the solvent and local irritation rather than to tissue growth.
• The pegylated version produces a specific argument, with some describing the longer half life as an advantage and others arguing it offers nothing over the unmodified peptide and may be worse. Nobody in what was read reports a result that separates the two.
• Disappointment and poor value are the dominant conclusions. People redirect others toward testosterone or IGF-1 instead, and vial prices are raised as not justified by what they observed.
• Doubt about whether the product was what it claimed runs through the discussion, which makes the negative reports as hard to interpret as the positive ones.

Sources: Mechano growth factor and PEG-MGF threads on EliteFitness, found by site-restricted search and read directly, September 2026. Nothing above is attributed to any specific post and no post is reproduced.

The state of the research

The evidence, in charts

The studies we cite

• Study in people2003
  Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise

  This is the study sold as human evidence for MGF, and nobody in it was given MGF. 8 younger men and 7 men in their seventies and eighties did heavy one-leg knee extensions, then had a small piece of thigh muscle taken. The younger men's muscle switched on more of the MGF gene message. The older men's did not. This measures what the body does after hard exercise. It says nothing about injecting a lab-made copy.

  8 men aged 25 to 36 and 7 aged 70 to 82 did 10 sets of 6 single-leg knee extensions at 80% of one-repetition maximum. MGF mRNA rose in the young group and not in the elderly group, IGF-IEa did not change in either, and resting MGF was roughly 100-fold lower than IGF-IEa. This is a study of the body's own transcription, not of an injected peptide.

  PMID 12562960 Journal of Physiology
• Review of studies2010
  Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration

  Independent groups dispute the E-peptide's biological activity.

  PMID 20130113 Endocrinology
• Review of studies2026
  Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks

  The regulator's list covers the PEG form, and it says nobody has been given that either. FDA names PEG-MGF and says it has found no data on anyone taking a product with it, by any route. The plain MGF sold on its own is not listed separately. So the page records an absence for one form and says nothing about the other. Neither is a statement that the peptide works or is safe.

  FDA's list names the pegylated form, PEG-MGF, and states it has identified no human exposure data on products containing it by any route. The native peptide sold as MGF is not separately listed. Updated 22 April 2026.

  Source U.S. Food and Drug Administration
• Lab (cells in a dish)2011
  MGF E-peptide activates human muscle progenitor cells

  Increased proliferation in cultured human cells.

  PMID 21354439 Mechanisms of Ageing and Development
• Lab (cells in a dish)2012
  MGF E-peptide effects on porcine satellite cells

  Proliferation in pig cells.

  PMID 22875667 Molecular and Cellular Biochemistry