PEG-MGF Dosage, Half-Life & Evidence Guide

PEG-MGF at a glance

What it is

The 24-aa C-terminal E-domain peptide of human IGF-1Ec (sequence YQPPSTNKNTKSQRRKGSTFEERK), covalently conjugated to one or more PEG chains. Commercial listings quote the core peptide as the C-terminally amidated form, C121H200N42O39, ~2,867 Da; the free acid of the same sequence is C121H199N41O40, ~2,868 Da. Not full-length IGF-1Ec, and not mature IGF-1.

What the PEG adds

Clearance resistance only. Chemically PEG-MGF differs from MGF by exactly one thing — the PEG group. There is no additional pharmacophore and no proposed change to the biology.

Studied for

Nothing, as the PEGylated form. Satellite-cell activation, myoblast proliferation and muscle repair were studied in cell culture and rodent models using the unPEGylated MGF E-peptide. No human study of administered MGF or PEG-MGF exists for any outcome.

Commonly reported range

200-400 mcg per administration in community and research-setting reports. No dose has ever been established in any species for the PEGylated form.

Route reported

Subcutaneous or intramuscular injection after reconstitution with bacteriostatic water. Not orally, nasally or transdermally bioavailable.

Reported frequency

2-3 times per week, in cycles of roughly 4-6 weeks. The reduced-frequency rationale rests entirely on a half-life that has never been measured for this compound.

Evidence status

Essentially none for PEG-MGF specifically — no published PK, toxicology, animal-efficacy or human data. For the unPEGylated parent peptide, supportive in-vitro and rodent work exists, largely from one originating group and its collaborators, but an independent 2014 replication attempt found no effect at all.

Regulatory status

Not approved by FDA for any indication, and not approved as a drug in any major regulated market. Placed in September 2023 on FDA's 503A Category 2 list of bulk drug substances that "may present significant safety risks," then removed from Category 2 in April 2026 after the nominations were withdrawn — a procedural removal that does not make it compoundable. FDA announced in April 2026 that its Pharmacy Compounding Advisory Committee would meet before the end of February 2027 to consider it. Not a controlled substance; cannot lawfully be sold as a dietary supplement.

WADA status

Prohibited at all times, in and out of competition. "Mechano growth factors (MGFs)" are named explicitly in Section S2.3 of the WADA Prohibited List, the growth factors and growth factor modulators category, including the edition in force for 2026. PEGylation confers no exemption, and mass-spectrometric detection methodology for MGF has been published.

Reported ranges from research/community — examples, not recommendations.

What it is / mechanism

A note on scope before the biology: because PEG-MGF is chemically the MGF 24-mer plus a PEG chain and nothing else, the underlying E-peptide biology is identical between the two compounds and is treated at full length in the separate MGF guide. What follows is a condensed version of that shared material, followed by the part that is genuinely specific to the PEGylated form — which is where this page spends its attention. The IGF1 gene does not produce a single protein. Alternative splicing — in the human case a reading-frame shift in exon 5 — yields several isoforms (IGF-1Ea, IGF-1Eb in rodents, IGF-1Ec in humans) that share the mature IGF-1 domain but carry different C-terminal E-domains. IGF-1Ec mRNA is transiently upregulated in mechanically loaded or damaged skeletal muscle, which is where the name "mechano growth factor" came from when Goldspink's group coined it in the mid-1990s. The proposed mechanism, originating with Yang and Goldspink, is that IGF-1Ec is post-translationally cleaved to release a free 24-amino-acid E-peptide with bioactivity independent of mature IGF-1: where mature IGF-1 signals through IGF-1R and PI3K/Akt to drive myoblast differentiation and protein synthesis, the E-peptide is proposed to act earlier, activating satellite cells and driving myoblast proliferation while delaying differentiation, thereby expanding the progenitor pool before fusion. Proposed downstream signals in the primary literature include ERK1/2 and, in some models, NF-kB and p38 MAPK. It is worth being precise about what is actually sold: research-market "MGF" and "PEG-MGF" are this 24-mer, not the full-length IGF-1Ec protein. Two mechanistic caveats belong in any honest treatment. First, no receptor for the E-peptide has ever been identified. The central marketing claim — that MGF acts through an IGF-1R-independent pathway — is a claim about the absence of a known receptor, not the presence of a characterized one. Second, the E-peptide is strongly basic: reading the published sequence YQPPSTNKNTKSQRRKGSTFEERK gives three arginines (positions 14, 15 and 23) and four lysines (positions 8, 11, 16 and 24) — seven basic residues in twenty-four. Several groups have argued that a substantial fraction of its reported cell-culture activity is consistent with non-specific polycationic membrane effects rather than receptor-mediated signalling. Compounding both points, endogenous free MGF E-peptide has never been isolated from cultured cells, conditioned medium, animal tissue or biological fluid. The mRNA is real and well documented; the free circulating peptide is inferential. The Matheny, Nindl and Adamo minireview in Endocrinology (2010) flags this explicitly and uses the word "putative" advisedly. The PEG half of the molecule is the part that is mechanistically uncontroversial. PEGylation is a well-established half-life-extension strategy: the attached polymer increases the conjugate's hydrodynamic radius above the glomerular filtration threshold, reducing renal clearance, and provides steric shielding against exopeptidase and endopeptidase attack. This is the same chemistry behind peginterferon, pegfilgrastim and pegloticase, and it is generalizable across peptides and proteins. Nothing about PEGylation is proposed to change what the peptide does; it changes only how long the peptide is around to do it. The consequence matters: PEGylation cannot rescue a biology that is not there. If the E-peptide has no real activity — which is what the 2014 replication failure suggests — then extending its half-life extends nothing. Which exposes the problem competitors almost universally skip: "PEG-MGF" is not a standardized chemical entity. Vendors do not disclose PEG chain length (claims range across roughly 2-40 kDa), PEG architecture (linear versus branched), or the conjugation site and chemistry. The 24-mer presents an N-terminal tyrosine amine plus four lysine side chains, so random amine PEGylation produces a heterogeneous mixture of positional isomers with potentially different bioactivity. Reported product masses range from "~2,867 Da plus PEG" to an apparent 7-12 kDa. The bare peptide is not perfectly uniform either: the ~2,867 Da figure quoted in commercial listings corresponds to the C-terminally amidated peptide (C121H200N42O39) rather than to the free acid of the same sequence (C121H199N41O40, ~2,868 Da), and anti-doping chemists have described a C-terminally amidated MGF analogue recovered from black-market material (Esposito and colleagues, Rapid Communications in Mass Spectrometry, 2012). An HPLC purity certificate of 98% or 99% does not resolve any of this, because it measures the homogeneity of a peak, not PEG identity, PEG size or attachment site. Two vials labelled "PEG-MGF" from different suppliers are not necessarily the same molecule, and any pharmacokinetic claim made about the compound is therefore vendor-specific and unverifiable. The honest summary: sound, well-understood chemistry applied to a peptide whose underlying biological activity has failed independent replication.

Researched effects

Every reported effect attributed to PEG-MGF is inherited wholesale from the unPEGylated parent peptide, because no study of the PEGylated form exists. That inheritance is worth stating plainly, because it is the step at which most pages about this compound quietly stop being accurate: findings obtained with a bare 24-mer in a dish or a mouse are presented as though they described the PEGylated conjugate sold in vials. In cell culture and rodent models the reported findings for the unPEGylated MGF E-peptide include satellite-cell activation and recruitment after injury, increased myoblast proliferation and migration, delayed differentiation, increased proliferative lifespan of human muscle progenitor cells, modulation of macrophage phenotype during the resolution phase of muscle repair, neurogenesis in the aging mouse brain, and improved cardiac function after myocardial infarction when the peptide was delivered locally and continuously from a matrix. These are real published findings in real models. They are also, with important exceptions, largely traceable to one originating research group and its collaborators, and none of them involves a human being receiving the compound. What users report is a different category of information entirely and should be read as such. Community reports describe localized fullness or "pump" at the injection site, a subjective sense of faster recovery between training sessions, and occasionally increased soreness. The local-fullness observation is frequently marketed as evidence of site-specific action; it is equally consistent with fluid shift from the injection volume itself, and anecdote cannot distinguish the two. Because there is no blinded human data of any kind, expectancy effects, concurrent training changes, and the near-universal practice of stacking PEG-MGF with GH secretagogues or IGF-1 analogues make individual reports uninterpretable as evidence of anything. The single most important item on this page is that the core mechanism failed independent replication. In 2014, Fornaro and colleagues at an independent industry laboratory — with David Glass, a senior figure in skeletal muscle biology, among the authors — tested synthetic MGF E-peptide across multiple cell types and found no increase in myoblast proliferation, no inhibition of differentiation, and no activation of the expected signalling pathways, while mature IGF-1 produced robust responses in the same assays. Their stated conclusion was that the results call into question whether there is a physiological role for MGF at all. That paper is the strongest single piece of published evidence bearing on the mechanism, and it belongs beside the foundational work rather than behind it. A reader deciding what to make of PEG-MGF should weigh it heavily: the proposed mechanism is not established fact, it is a contested hypothesis with one prominent failed replication against it — and PEG-MGF adds a delivery modification on top of that hypothesis without adding any evidence for it.

Dosage — reported ranges (overview)

There is no clinical protocol for PEG-MGF and no dose has ever been established in any species for the PEGylated form. Everything below describes what is commonly reported in research and community settings, and is presented for reference only — not as a recommendation and not as a protocol to follow. The figures most often cited are 200-400 mcg per administration by subcutaneous or intramuscular injection, given two to three times per week, in cycles of roughly four to six weeks followed by a comparable off period. Some reports describe splitting a dose bilaterally into worked muscle groups at 100-200 mcg per side; others describe deliberately dosing on rest days on the reasoning that endogenous IGF-1 is lower then. Neither practice has any supporting data whatsoever. The entire rationale for two-to-three-times-weekly dosing rather than native MGF's near-daily, immediately-post-training schedule is the claimed PEG-driven half-life extension. That claim has no published measurement behind it, which makes the frequency logic circular. It also produces a contradiction worth pointing out, because it is a useful test of whether a source is thinking or copying: many community protocols simultaneously insist on injecting within about thirty minutes of training — a timing rule carried over from native MGF, where a minutes-long half-life makes the window at least internally coherent — while also asserting a multi-day half-life. Both cannot be true. If PEG-MGF really circulated for 48-72 hours, post-workout timing would be irrelevant. If timing genuinely matters, the half-life claim is wrong. Any protocol asserting both is repeating two incompatible pieces of folklore. For scale, the published preclinical work was done on the unPEGylated peptide in cell culture and small rodents, using absolute quantities far below the hundreds of micrograms described in community practice — and in the cardiac work the peptide was delivered locally and continuously from a matrix rather than injected systemically at all. Specific rodent per-injection figures circulate online, but they are not reliably traceable to the source papers, so no numeric conversion is offered here. The structural point survives without one: the animal literature provides no dose-translation basis for the numbers circulating for human use. Those numbers were arrived at by convention and vial economics, not by scaling from anything. Given the complete absence of human safety data, the blanket WADA prohibition, and the unresolved FDA compounding status, this material is not appropriate for human use in any dose. The ranges above are documented here only because readers encounter them and deserve accurate context on where they came from.

The full step-by-step protocol examples, titration schedule, and a printable protocol sheet with a dosing and injection log are included in the paid Protocol Playbook for this guide.

Reconstitution — bac-water math

PEG-MGF is supplied as a lyophilized powder, most commonly in 2 mg or 5 mg vials. Reconstitution with USP-grade bacteriostatic water is a straightforward arithmetic exercise: total peptide mass in micrograms divided by the volume of diluent added gives the concentration, and the intended dose divided by that concentration gives the volume drawn. On a U-100 insulin syringe, 1.00 mL equals 100 units, so 0.20 mL is 20 units. The two example columns below use 200 mcg and 400 mcg, the low and high ends of the commonly reported range; intermediate figures follow the same arithmetic, so at 2,000 mcg/mL a 300 mcg dose would be 0.15 mL, or 15 units. The dilution chosen changes only the volume drawn, never the amount of peptide in the vial — a 2 mg vial contains 2,000 mcg whether 1 mL or 2 mL is added. More diluent buys measurement precision on small draws; less diluent means smaller injection volumes. One PEG-specific caveat applies to every row: because PEG conjugates can behave differently from their parent peptides in solution, and because vendors do not disclose PEG chemistry, stability data from any other peptide should not be assumed to transfer here.

This is concentration math, not a dose recommendation.

Injection / administration basics

Handling described in research settings follows the standard lyophilized-peptide procedure. Both the peptide vial stopper and the bacteriostatic water stopper are wiped with alcohol and allowed to dry. The measured volume of bacteriostatic water is introduced slowly and angled so that it runs down the inner wall of the vial rather than jetting directly onto the powder cake — PEG conjugates and small peptides alike are described as sensitive to shear and to air-liquid interface exposure. The vial is then left to dissolve, with gentle swirling or rolling between the palms if required, and is never shaken. A properly reconstituted vial is described as yielding a clear, colourless solution with no visible particulates, cloudiness or fibrous strands; anything else is treated as a reason not to use the vial. The routes described in reported use are subcutaneous injection with a short insulin syringe (typically 29-31 gauge, 8-13 mm) at a 45-90 degree angle into subcutaneous tissue, or intramuscular injection. Neither the peptide's size nor its chemistry permits oral use — a 24-mer is digested — and it is not viable intranasally or transdermally at meaningful doses. Injection is the only route in reported use. Standard aseptic practice is described throughout the handling literature: one new sterile needle per injection, no reuse or recapping of needles, rotation of sites so that the same spot is not used repeatedly, and disposal of sharps into a proper container. Non-sterile injection technique is a documented route to abscess formation and bloodborne infection, and research-use-only material is not manufactured to pharmaceutical sterility standards, which raises rather than lowers the stakes. One PEG-specific point on measurement deserves emphasis, because it undercuts the confidence the table above might otherwise invite. Since vendors do not disclose PEG molecular weight, the labelled "mass" on a PEG-MGF vial may or may not refer to peptide mass alone. If a vial is labelled by total conjugate mass and the PEG chain accounts for a substantial fraction of that mass, the actual peptide content is proportionally lower than the arithmetic assumes — potentially by a large factor at the high end of the claimed PEG size range. Nothing on the label, and nothing on a standard HPLC certificate, resolves which convention a given supplier used. The arithmetic in the table is correct; the input mass it depends on may not be.

Half-life & frequency rationale

This is the single most misreported fact about PEG-MGF, so it is worth being precise. Native, unPEGylated MGF E-peptide is reported to clear very quickly — on the order of minutes. The widely repeated "5-7 minutes" figure is biologically plausible for a small, unstructured, highly basic 24-mer with no carrier-protein binding (unlike mature IGF-1, which is stabilized in circulation by IGF binding proteins), but it is not traceable to a clean published human pharmacokinetic measurement either. For PEG-MGF, no pharmacokinetic data exists at all — not in humans, not in animals, not published anywhere. The ubiquitous "48-72 hours" figure, and its variants ("2-3 days," "up to a week"), are vendor and forum copy with no measurement behind them. Some more cautious secondary sources say "several hours." Both are guesses, and neither should be repeated as fact. What can be stated with confidence comes from the general PEGylation literature rather than from this compound: PEGylation reliably extends the circulating half-life of peptides in this size range, frequently by one to two orders of magnitude, by pushing hydrodynamic radius above the renal filtration cutoff and sterically blocking protease access. The magnitude of that extension scales with PEG molecular weight and architecture. Since PEG-MGF vendors disclose neither, the actual half-life of any given vial is genuinely unknown and may differ substantially between suppliers — a 2 kDa linear PEG and a 40 kDa branched PEG do not produce remotely similar pharmacokinetics. The accurate framing is therefore: PEGylation would be expected to extend half-life substantially relative to native MGF's minutes-long clearance, because that is well-established chemistry; the specific "48-72 hour" figure circulated online has never been measured for this compound and should not be treated as a fact. There is also a moving target here that the fixed-number framing hides entirely. Anti-PEG antibodies, which a meaningful proportion of the population carries without any prior exposure to PEGylated drugs and which repeat dosing can raise further, accelerate the clearance of PEGylated agents. Whatever half-life a first injection has need not hold on the tenth. Any single number quoted for a PEGylated agent is at best a first-dose number.

Stacking — overview

Stacking discussion for PEG-MGF is entirely a description of community practice, not a set of validated combinations. No combination involving PEG-MGF has been studied in any model, and combining multiple unstudied compounds multiplies the unknowns rather than averaging them — if something goes wrong, there is no way to attribute it. The stacks below are documented because they are what people actually report, and readers are better served by an accurate map of the landscape than by a blank page. The internal logic community users give for these pairings is worth understanding even where it is unsupported. GH secretagogue pairings (CJC-1295 with ipamorelin, or mod-GRF 1-29) are justified on the reasoning that raising pulsatile GH raises hepatic IGF-1 output, which in the Goldspink model is the upstream source of the IGF-1Ec transcript; PEG-MGF is then framed as supplying the downstream E-peptide directly. That reasoning assumes the very mechanism Fornaro and colleagues failed to reproduce. IGF-1 LR3 pairings are justified on a complementarity argument — mature IGF-1 analogue driving differentiation and protein synthesis, E-peptide driving proliferation — which is elegant and completely unvalidated in combination. Repair-peptide pairings with BPC-157 and TB-500 are simply co-mentions in recovery-focused protocols, with no proposed interaction at all. Two practical notes apply regardless of the combination. First, because everything in these stacks is unstudied, any adverse effect is uninterpretable — there is no way to know which component produced it. Second, PEG-MGF, MGF, IGF-1 and its analogues, and GH secretagogues are all captured by WADA Section S2, so stacking multiplies anti-doping exposure without adding any defence. Readers exploring the adjacent chemistry will find it covered in our other peptide guides — the MGF guide carries the full treatment of the underlying E-peptide biology that this page deliberately condenses, and the IGF-1 LR3 guide covers the mature-analogue side of the IGF axis. Medibact publishes guides and supplies USP-grade bacteriostatic water; it does not sell peptides.

For how combinations are grouped by research context, the named blends, and why a pre-mixed blend vial cannot be calculated from its total milligrams, see the peptide stacks guide.

Storage & handling

• Lyophilized powder: handling documentation describes sealed vials stored refrigerated at 2-8°C for routine use, or frozen at -20°C or below for longer-term storage, kept in original packaging or otherwise protected from light. Dry lyophilized peptide is the most stable form the material takes, which is why reconstitution is generally described as a step deferred until a vial is about to be put into use.
• After reconstitution with bacteriostatic water, two separate limits apply and the shorter of the two governs. The bacteriostatic water itself carries a 28-day in-use period after first puncture under USP and manufacturer labeling — that is the documented window for the benzyl alcohol preservative, and it is a hard limit regardless of what is dissolved in it. Peptide stability in solution is a separate question, and for PEG-MGF there is no published stability study at all; PEG conjugates can differ from their parent peptides in solution-phase behaviour, so figures quoted for other peptides do not transfer. Reconstituted vials are described as refrigerated at 2-8°C and protected from light. Any interval seen quoted for PEG-MGF specifically should be read as an assumption rather than a measurement.
• Reconstituted vials are described as never shaken. Agitation and air-liquid interface exposure denature peptides; gentle swirling or rolling is the handling described instead. Repeated freeze-thaw cycles of reconstituted solution are generally avoided altogether — freezing a reconstituted peptide is usually described as worse than working within a shorter refrigerated window.
• Visual inspection before each withdrawal is standard in handling guidance. A usable solution is described as clear and colourless with no particulates, cloudiness, discolouration or fibrous strands. Anything visible in the vial is treated as grounds for discard rather than for filtering or salvage.
• Bacteriostatic water rather than sterile water is what makes multiple withdrawals from one vial possible — the benzyl alcohol preservative is the reason, and plain sterile water carries no preservative and no in-use period at all. Handling descriptions also include wiping the stopper with alcohol before each entry, a new sterile needle for every withdrawal, and labelling the vial with its reconstitution date and resulting concentration so that the arithmetic and the 28-day clock do not have to be reconstructed from memory later.

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