PEG-MGF vs TB-500
A supercharged version of your muscle's natural repair signal—PEGylated Mechano Growth Factor stays active for days instead of minutes, waking up dormant stem cells to rebuild and strengthen damaged muscle tissue.
A powerful fragment of thymosin beta-4 that acts like your body's repair signal—speeding up healing of muscles, tendons, and tissues by promoting cell migration and new blood vessel growth right where you need it most.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
PEG-MGF
200–400 mcg
TB-500
2–2.5 mg
Frequency
PEG-MGF
Twice weekly
TB-500
Twice weekly
Administration
PEG-MGF
Subcutaneous injection
TB-500
Subcutaneous injection
Cycle length
PEG-MGF
4-6 weeks
TB-500
4-6 weeks
Onset speed
PEG-MGF
Moderate (1-2 weeks)
TB-500
Moderate (1-2 weeks)
Evidence level
PEG-MGF
Strong preclinical (extensive animal studies)
TB-500
Moderate human trials (Phase 1-2)
Benefit ratings
Muscle Recovery
Stem Cell Activation
Tissue Healing
Healing Speed
Tissue Repair
Anti-Scarring
Compound specifications
PEG-MGF
Molecular formula
C121H200N42O39 (peptide core)
Molecular weight
2867.2 g/mol (peptide) + PEG moiety
Half-life
48-72 hours (vs. minutes for unmodified MGF)
Bioavailability
High when injected subcutaneously or intramuscularly; PEGylation protects from rapid degradation
CAS number
108174-48-7
TB-500
Molecular formula
C38H68N10O14
Molecular weight
889.01 g/mol
Half-life
2-3 days (systemic)
Bioavailability
High via subcutaneous injection (~100%)
CAS number
885340-08-9
Dosing compared
PEG-MGF
Subcutaneous
200 mcg
2-3x per week, post-workout · 5-6 week cycle
Lower end of reported community practice [6]. Important: PEG-MGF is a research peptide with no human clinical trials - all dosing is extrapolated from animal data and self-reported use, not established medicine [1][2]. Pegylation extends its half-life versus native MGF.
200-400 mcg
2-3x per week, post-workout · 5-6 week cycle, then time off
Typical reported research-use range, injected near the trained muscle or into abdominal fat shortly after training [6]. This is community practice, not a clinically validated dose; preclinical work shows MGF activates muscle satellite/progenitor cells [1][2].
TB-500
Subcutaneous
2-2.5 mg
Twice weekly · Loading phase, 4-6 weeks
Research peptide with no human trials of the fragment; [9] loading doses used in practice [6].
2-2.5 mg
Once weekly · Maintenance after loading
Maintenance dose used in practice following the loading phase [6].
Best suited for
PEG-MGF
Athletes Recovering from Muscle Injuries
If you've pulled, strained, or torn a muscle, PEG-MGF could be a game-changer. It activates the satellite cells (muscle stem cells) that your body uses to repair damaged fibers, potentially speeding up your return to training.
Serious Lifters and Bodybuilders
Heavy training creates microdamage in your muscles—that's actually how they grow. PEG-MGF amplifies your body's repair response, potentially helping you recover faster between sessions and make more gains from each workout.
Older Adults Concerned About Muscle Loss
As we age, our muscles become less responsive to the 'repair and grow' signals. Research shows older adults don't produce as much MGF after exercise. Supplementing with PEG-MGF might help restore some of that youthful repair capacity.
Post-Surgical Recovery (Under Medical Supervision)
If you're recovering from surgery involving muscle tissue, PEG-MGF's ability to recruit stem cells and promote tissue repair could support faster healing. Always use under medical guidance in these situations.
TB-500
Athletes Recovering from Muscle Injuries
If you've pulled a hamstring, strained your back, or torn a muscle, TB-500 helps accelerate the healing process by promoting cell migration to the injury site and supporting new blood vessel growth. It's especially useful for injuries that just won't seem to fully heal [1][5].
Tendon and Ligament Problems
Tendons and ligaments are notoriously slow healers because they have poor blood supply. TB-500 promotes angiogenesis (new blood vessel formation) and helps repair these stubborn connective tissue injuries—think Achilles tendonitis, tennis elbow, or rotator cuff issues [5].
Post-Surgical Recovery
After surgery, your body needs to repair a lot of tissue quickly. TB-500 supports wound healing, reduces inflammation, and may help minimize scar tissue formation. Some protocols use it alongside traditional recovery to potentially speed up the healing timeline [1][4].
Chronic Inflammation and Slow Healers
Some people just heal slowly—whether due to age, diabetes, or other factors. TB-500 helps regulate the inflammatory response and promotes the cellular processes needed for tissue repair. It essentially tells your body to focus healing resources where they're needed most [1].
Side effects
PEG-MGF
Common
- Injection site irritation
- Mild headache
- Temporary fatigue
Uncommon
- Localized swelling
- Blood sugar fluctuations
Serious
- Allergic reaction
TB-500
Common
- Injection site redness
- Mild fatigue or lethargy
- Mild headache
- Slight flushing
Uncommon
- Head rush or lightheadedness
- Temporary nausea
Serious
- Allergic reaction
Safety & evidence
PEG-MGF
Evidence level
Strong preclinical (extensive animal studies)
FDA status
Research compound
Safety overview
PEG-MGF (pegylated mechano growth factor) demonstrates good tolerability in preclinical studies with minimal immunogenicity from pegylation modifications. Intramuscular administration shows local tissue responses consistent with growth factor activity. No serious systemic adverse events in animal models at therapeutic doses. Pegylation extends half-life from 2 hours (native IGF-1 Ec) to 24+ hours, reducing injection frequency while maintaining safety profile similar to parent peptide.
Contraindications
- Active cancer or history of cancer
- Pregnancy or breastfeeding
- Known allergy to peptide components or PEG
- Children and adolescents
- Uncontrolled diabetes
TB-500
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
TB-500 has shown a good safety profile across preclinical studies and limited human research. It's a fragment of thymosin beta-4, a naturally occurring protein in your body involved in healing. Most side effects are mild and transient, primarily injection site reactions. However, large-scale clinical trials are still needed to fully establish its safety profile in humans [1].
Contraindications
- Pregnancy or planning to become pregnant
- Currently breastfeeding
- Active cancer or history of cancer
- Known allergy to peptide components
- Children and adolescents
Which is right for you?
Choose PEG-MGF if...
- Muscle injury recovery
- Post-workout muscle repair
- Combating muscle wasting
- Supporting bone healing
Choose TB-500 if...
- Accelerating injury recovery
- Tendon and ligament healing
- Reducing chronic inflammation
- Post-surgical recovery support