PEG-MGF: Dosage, Side Effects and Legal Status
PEG-MGF dosage, side effects and legal status: what FDA and WADA actually say, since no study reports a quantified human dose.
The short version
PEG-MGF is a lab-made, PEGylated version of mechano growth factor, an IGF-1-related peptide that animal research suggests muscle makes locally after training damage. No regulator has approved it, and FDA says it has identified no human exposure data on it at all. It is banned in sport at all times.
- Not FDA-approved for any use; sold only as a research chemical.
- FDA states it has identified no human exposure data on PEG-MGF by any route of administration.
- The muscle-growth story rests on animal research into a related natural peptide, not human trials of PEG-MGF.
- Banned at all times in sport under the WADA 2026 Prohibited List, S2.3.
PEG-MGF at a glance
- What it is
- Synthetic PEGylated analogue of a splice variant of IGF-1 (mechano growth factor)
- Main use
- Marketed to consumers for muscle repair and growth after resistance training. Never approved for human use; FDA states it has identified no human exposure data on it by any route.
- Also called
- Pegylated Mechano Growth Factor, PEGylated MGF, IGF-1Ec peptide analogue
- Evidence
- Animal / lab only
- US status
- Research use only
- Half-life
- Not established in humans
- How it is taken
- Subcutaneous injection
- Common protocol
- 200-400 mcg, 2-3 times a week, post-workout, for 4-6 weeks (common practice, not trial-established) Dosage chart
PEG-MGF is sold online as a peptide for muscle growth and faster recovery after training. It is not an FDA-approved drug, and no completed human trial has tested it. FDA’s own compounding-safety page says the agency has identified no human exposure data on it at all.
Dosing: why there is no established dose.
US legal status - Research use only
Sold for laboratory research use only. Not approved by the FDA for human use, and cannot be lawfully marketed as a supplement or a medicine. Products sold this way are not made to pharmaceutical quality standards, and their contents are not verified by anyone.
What is PEG-MGF?
Mechano growth factor (MGF) is a peptide made from an alternative version (a splice variant) of the IGF-1 gene. Animal and cell research suggests muscle makes it locally after mechanical damage, the kind training causes. That is separate from the IGF-1 the liver releases into the blood.
PEG-MGF is a synthetic copy of the end section (the C-terminal peptide) of that MGF, with polyethylene glycol attached (PEGylation). Vendors say the PEGylation extends a very short natural half-life. I could find no published human study measuring that, so it is a marketing claim, not a figure.
The papers on natural MGF’s biology are not yet in my source registry, so I describe it here in general terms rather than tie a finding to a citation I can’t link.
PEG-MGF benefits: what the research shows
No trial has given PEG-MGF to people and measured an outcome. The research behind it is rodent and cell work on natural MGF. That work was designed to study gene activity after muscle injury, not to test whether a synthetic, PEGylated peptide is safe or effective.
So the animal research doesn’t show that PEG-MGF, the product actually sold, does anything for a person who injects it. No adequately powered, controlled human trial has tested it for muscle growth, recovery or anything else it is marketed for.
PEG-MGF dosage
The common PEG-MGF dose is 200-400 mcg, 2-3 times a week, post-workout. From a 2 mg vial mixed with 2 mL of bacteriostatic water, 300 mcg is 30 units (0.3 mL) on a U-100 insulin syringe.
The protocol most often used is 200-400 mcg injected under the skin 2-3 times a week, usually after training, for 4-6 weeks, then at least a 4-week break. That is common practice, not a dose any study has set.
There is no trial or regulator figure to give instead. FDA has identified no human exposure data, and no published animal study reports a measured injected dose. With no human half-life study either, no dosing interval can be based on one. Full detail and the reconstitution calculator: PEG-MGF dosage.
PEG-MGF side effects
There is no human safety data: no trial, case report or FDA label to build a side-effect list from.
FDA’s compounding-safety review flags 2 open concerns, not reactions seen in a person:
- a risk of immune reactions (immunogenicity) for some routes of use
- difficulty characterising the active ingredient and its impurities.
PEG-MGF works on the same signalling pathway as IGF-1, so the wider class raises a general concern about insulin sensitivity and growth signalling. That is inferred from the shared pathway, not from a study of PEG-MGF, so treat it as a reason for caution rather than a measured risk.
PEG-MGF is injected under the skin. For redness, itching or swelling at the injection site, see injection-site reactions; no study has looked at this for PEG-MGF itself.
Is PEG-MGF legal?
PEG-MGF is not FDA-approved for any use in the US. It is not legally marketed for human use and is sold as a research chemical, usually labelled not for human use.
FDA’s compounding list
FDA’s bulk drug substances safety-risk page (current as of 22 April 2026) lists PEG-MGF under “bulk drug substances nominated but withdrawn”. These substances were once flagged in Category 2 of FDA’s interim compounding policies, and then the people who nominated them withdrew the nominations.
FDA keeps its original safety language for PEG-MGF on that page: no human exposure data by any route, a risk of immune reactions, and difficulty characterising the active ingredient. Leaving Category 2 is not a safety clearance. Nor does it put PEG-MGF on the 503A Bulks List, which a pharmacy must check before it may legally compound a substance. PEG-MGF was not on that list when this page was published. More on how this works: my US peptide regulation tracker.
Sport
PEG-MGF is banned at all times, in and out of competition. The WADA 2026 Prohibited List names “Mechano growth factors (MGFs)” under S2.3, Growth Factors and Growth Factor Modulators, alongside IGF-1 and its analogues. If you are a tested athlete, check the current WADA list yourself rather than relying on a vendor, a review or this page.
I checked only US federal law and the current WADA list, not US states or other countries.
Related compounds
PEG-MGF is often marketed alongside other unapproved growth-hormone-axis and IGF-1-pathway peptides:
- CJC-1295 - a synthetic GHRH analogue that raises IGF-1 throughout the body. Unapproved, and named in the WADA 2026 Prohibited List under S2.2.4.
- MOTS-c - a different, mitochondria-derived peptide. Its human studies measure it rising with exercise rather than being injected, and it is also sold as a research chemical.
How PEG-MGF compares
Growth hormone and growth factors. Doses for unapproved compounds are common practice, not trial-established. All growth hormone and muscle peptides →
| Compound | Main use | Evidence | Usual dose | US status |
|---|---|---|---|---|
| HGH 191AA | Marketed to consumers for body recomposition, recovery and anti-aging in adults who do not have a diagnosed growth hormone deficiency. The identical molecule, somatropin, is FDA-approved by prescription for defined deficiency and wasting conditions - see the "Where approved somatropin fits" section on the main guide for that distinction. | Limited human data | 333-1333 mcg, Once daily (split into a morning and evening dose above roughly 3 IU/day), subcutaneous | Research use only |
| IGF-1 LR3 | Originally engineered as a laboratory reagent - an IGF-1 variant with reduced binding to IGF-binding proteins, used to study IGF-1 signalling in cell culture. Sold to consumers as a research chemical for muscle growth, a use with no controlled human trial behind it. | Animal / lab only | 20-50 mcg, once daily | Research use only |
| IGF-1 DES | Originally isolated and studied as a naturally occurring IGF-1 fragment in laboratory pharmacology, used to probe IGF-1 receptor signalling with reduced interference from binding proteins. Sold to consumers as a research chemical for localised, site-specific muscle growth, a use with no controlled human trial behind it. | Animal / lab only | 20-120 mcg, on training days only, about 4-5 times a week, not on rest days | Research use only |
| MGF | Marketed to consumers as a peptide injected directly into a trained muscle immediately after exercise, for local muscle repair and growth. No completed human trial has tested it for this or any outcome. | Animal / lab only | 100-400 mcg, Immediately post-workout, 2-3 times a week (training days only) | Research use only |
| PEG-MGF | Marketed to consumers for muscle repair and growth after resistance training. Never approved for human use; FDA states it has identified no human exposure data on it by any route. | Animal / lab only | 200-400 mcg, 2-3 times a week, post-workout | Research use only |
| Follistatin | The body's own brake on activin and myostatin signalling, studied academically as a gene-therapy payload for muscle-wasting disease. Sold separately, as an injected research-chemical protein, for grey-market muscle-building use that its own human trials have never tested. | Animal / lab only | 100-500 mcg, 2 to 4 times a week | Research use only |
Where to buy PEG-MGF for research
Each vendor is checked against my vendor checklist.
1.Next Level PharmFeatured
2 mg vial
- No FDA warning letter found
- Names its testing lab
- Batch COAs published
- Takes card payment
2.BioEdge Research Labs
5 mg vial
- No FDA warning letter found
- Names its testing lab
- Batch COAs published
Common questions
What is the usual PEG-MGF dose?
The most common protocol is 200-400 mcg injected under the skin 2-3 times a week, usually after training, for 4-6 weeks, then at least a 4-week break. That is common practice, not a tested dose. FDA has identified no human exposure data, and no published animal study reports a measured injected dose. Full detail: [PEG-MGF dosage](/peg-mgf-dosage/).
Does PEG-MGF work for muscle growth?
No completed human trial has tested injected PEG-MGF for muscle growth, recovery or anything else. The research behind the claims is animal and cell work on the natural peptide it copies, not on the synthetic product people buy.
Is PEG-MGF legal in the United States?
It is not an FDA-approved drug. FDA's bulk drug substances safety-risk page lists it as "nominated but withdrawn": it was once flagged as a possible significant safety risk, then the nominator withdrew it. That is not a safety clearance, and it is not on the list pharmacies may compound from. It is sold as a research chemical labelled not for human use.
Is PEG-MGF banned in sport?
Yes. The WADA 2026 Prohibited List names "Mechano growth factors (MGFs)" under S2.3, Growth Factors and Growth Factor Modulators. They are banned at all times, in and out of competition.
What is the difference between MGF and PEG-MGF peptides?
MGF is the natural peptide, made from a splice variant of the IGF-1 gene, that research suggests muscle makes locally after damage. PEG-MGF is a lab-made copy of its end section (the C-terminal fragment) with polyethylene glycol attached, which the natural molecule lacks. Vendors say this makes it last longer in the body, but no published human study has measured that. FDA has identified no human exposure data for PEG-MGF, whatever name a seller uses.
What are the potential side effects of PEG-MGF peptide therapy?
There is no established side-effect profile, because no completed human trial has tested it and FDA has identified no human exposure data. FDA flags a risk of immune reactions for some routes and difficulty characterising the peptide and its impurities. Because it shares IGF-1's pathway, there is a general concern about insulin sensitivity and growth signalling, based on the pathway rather than a study. Unregulated research chemicals also carry manufacturing and purity risk.
Does MGF build muscle?
No completed human trial shows that MGF, or the synthetic PEG-MGF sold online, builds muscle in people. The idea rests on animal and cell research suggesting muscle makes a natural IGF-1 variant locally after exercise damage. That research studied gene activity, not whether giving the peptide to a person adds muscle.
What is the strongest peptide for building muscle?
No peptide has been shown in human trials to be the "strongest" for muscle. None of those marketed this way is FDA-approved for muscle growth, and none has been tested head-to-head in controlled human research. Potency rankings of PEG-MGF, MGF and similar peptides rest on marketing and anecdote. I don't rank or recommend compounds for muscle building.
What is the most risky peptide?
I can't rank PEG-MGF, or any peptide, by risk. Most research peptides, PEG-MGF included, have no completed human safety trial, so there is no controlled evidence to compare. FDA has identified no human exposure data on PEG-MGF, which is a documented absence of safety information, not a measured risk. This site's safety page explains the difference.
References (2 sources)
Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.
- 1.FDA - Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (lists PEG-MGF in the "nominated but withdrawn" table, page current as of 04/22/2026)- US Food and Drug Administrationregulatory
- 2.WADA 2026 Prohibited List, section S2.3 - Growth Factors and Growth Factor Modulators, naming "Mechano growth factors (MGFs)" explicitly (national anti-doping agency mirror, PDF)- Jamaica Anti-Doping Commission (mirroring the World Anti-Doping Agency 2026 Prohibited List)regulatory