TB-500
Also known as Thymosin Beta-4 fragment, TB4, LKKTETQ, Tbeta4 (17-23)
TB-500 is a synthetic version of the active region of thymosin beta-4, a protein found in nearly every human cell that regulates actin and cell movement. It is used for injury recovery, flexibility and general tissue repair, usually alongside BPC-157.
Reviewed by the amino101 editorial team. , first published .
Quick start
What people commonly do. Not a prescription.- Typical dose
- 2 to 5 mg
- How often
- twice weekly during loading, then weekly or every other week
- Where
- Subcutaneous, belly; does not need to be near the injury
- Timing
- any time, food does not matter
- Effects timeline
- flexibility and reduced stiffness 1 to 2 weeks, injury recovery 4 to 6 weeks
- Storage
- fridge 2 to 8 C once mixed, use within 4 weeks; powder in the freezer or fridge away from light
- Cycle length
- 4 to 6 week loading phase, then maintenance or stop
- Break between
- 4 to 8 weeks, or stop once the injury has healed
Overview
Thymosin beta-4 is a 43 amino acid protein that is one of the most abundant small proteins inside cells. It binds actin and controls how cells build their internal scaffolding, which is essential for cell migration, wound closure and blood vessel formation. TB-500 as sold on the research market is usually a short synthetic fragment, most often the 7 amino acid actin-binding segment, though some vendors sell the full length protein under the same name. This ambiguity matters when comparing products and doses.
Full length thymosin beta-4 has been studied in animals for cardiac repair after heart attack, corneal healing, skin wound closure and hair growth. Rodent and canine models show improved recovery of heart muscle, faster epithelial repair and reduced scarring. The protein appears to recruit progenitor cells into damaged tissue and dampen inflammation while it does so. Veterinary use in horses for tendon and ligament injuries is widespread and is where much of the practical experience with the compound comes from.
In humans, full length thymosin beta-4 was taken through phase 2 trials by RegeneRx for dry eye, corneal wounds and pressure ulcers, with modest positive results in eye conditions. Those trials used a pharmaceutical grade product, not the fragment that most people buy. There are no human trials of the fragment for sports injuries. The widespread use in racehorses and among athletes rests entirely on animal data and anecdote.
How it works
Thymosin beta-4 sequesters G-actin monomers and regulates actin polymerization, which controls how cells change shape and move. By releasing actin at the right moment it lets endothelial cells, keratinocytes and progenitor cells migrate into a wound. It upregulates matrix metalloproteinases that clear damaged tissue and promotes new capillary formation. It also reduces inflammatory cytokine release and lowers apoptosis in stressed cells. The short TB-500 fragment contains the actin-binding motif and is assumed to carry these effects, though it likely lacks some functions of the full protein. Because it is small and water soluble it distributes systemically rather than acting only where injected.
Where the research stands
Soft tissue injury and general recoveryModerate evidence
- Tendon and ligament injury. Rodent and horse data, plus long veterinary use in racehorses; no human trial of the fragment for sports injury.
- Muscle injury and flexibility. Mechanistic rationale from actin regulation and anecdote; no controlled data in people.
- Skin wounds. Rodent studies including aged and diabetic mice show faster full thickness wound closure with full length thymosin beta-4.
Eye surface healingModerate evidence
- Dry eye and neurotrophic keratopathy. Phase 2 randomized trials of thymosin beta-4 eye drops showed improved healing; this used the full protein, not the fragment sold as TB-500.
Cardiac repairEmerging
- Heart muscle recovery after heart attack. Mouse studies show smaller scars and better function; a small human safety trial in heart disease was run but did not lead to further development.
Hair growthWeak or mixed
- Hair regrowth. Mouse follicle stem cell studies only; human reports are anecdotal side observations.
- rodentImproved cardiac function and reduced scar size after induced heart attack in mice, with cardiomyocyte survival and vessel growth.
- rodentAccelerated full thickness skin wound closure in rats and in aged or diabetic mice.
- rodentPromoted hair follicle stem cell migration and hair growth in mice.
- human RCTPhase 2 trials of thymosin beta-4 eye drops showed improved healing in neurotrophic keratopathy and dry eye symptoms.
- rodentReduced inflammation and improved healing of tendon and ligament tissue in equine and rodent models.
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 1.5 h against dosing every 3.5 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.
Plasma clearance is fast, but the community schedule of twice weekly then weekly rests on the idea that the peptide saturates tissue and that its effects on cell migration outlast its presence in blood, which is an assumption rather than a measured fact.
TB-500 dosage and protocols
The usual pattern is a 4 to 6 week loading phase at 2 to 2.5 mg twice weekly, then a drop to 2 mg every one to two weeks for maintenance or a full stop. Loading is a community convention, not something taken from a human trial, and many people simply dose twice weekly for the whole cycle.
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Loading phase | 2 to 2.5 mg | twice weekly | Subcutaneous, abdomen |
| Maintenance | 2 mg | every 1 to 2 weeks | Subcutaneous, abdomen |
| Acute injury, higher end | 5 mg | twice weekly for 2 to 4 weeks | Subcutaneous or intramuscular |
| Flexibility and general recovery | 2 mg | once weekly | Subcutaneous, abdomen |
Timing relative to food, sleep or training does not appear to matter. Because it works systemically, the injection site is chosen for comfort, and people often separate it from BPC-157 by a few hours or use different sites so any injection reaction is easy to trace.
Community protocols typically load at 2 to 2.5 mg twice weekly for 4 to 6 weeks, then drop to 2 mg every one to two weeks.
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 |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 40 units |
| 10 mg | 1 mL | 10 mg/mL | 20 units |
How to reconstitute TB-500
- 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
Reduced stiffness and better range of motion are the earliest common reports; some people feel briefly tired or flushed after the first few doses.
- Week 3 to 6
Injury recovery is usually judged here, with less pain under load in tendon or muscle problems; this is the end of the typical loading phase.
- Beyond week 6
Maintenance dosing is meant to hold gains; if there has been no change by now, continuing is unlikely to help.
Interactions and stacking
BPC-157synergistic
The most common recovery stack; BPC-157 is dosed near the injury while TB-500 covers systemic cell migration and inflammation.
GHK-Cucompatible
Both promote cell migration and vessel growth and are combined for wound and surgical recovery; inject separately because of the copper.
Ipamorelincompatible
Growth hormone secretagogues are often run alongside recovery peptides; no known interaction, but the combination is untested.
IGF-1 LR3caution
Stacking two compounds that both drive cell growth and migration adds to the theoretical cancer concern without any safety data.
Active cancer treatmentavoid
Thymosin beta-4 is expressed in many tumor types and drives cell migration, so it should not be used by anyone with an active or recent cancer.
Blood pressure medicationcaution
Some users report head rush or lightheadedness after larger doses, which may add to the effect of antihypertensives.
Safety
- ▲Fatigue, lethargy or a head rush for a few hours after larger doses
- ▲Headache
- ▲Injection site redness or mild bruising
- ▲Nausea or flushing shortly after a dose
- ▲Occasional lightheadedness on standing
- ▲Human data on the fragment used in the research market is essentially nonexistent.
- ▲Thymosin beta-4 is expressed in many tumor types and drives cell migration, so it is a theoretical concern for anyone with active cancer.
- ▲Prohibited by WADA and widely tested for in horse racing.
- ▲Some users report fatigue, head rush or lethargy for a few hours after larger doses.
- ▲Vendors sell both the 7 amino acid fragment and the 43 amino acid protein as TB-500. Check which you are buying.
- ■A new lump, mass or skin lesion appears, given the cell migration and tumor concern
- ■Persistent fatigue or lightheadedness that does not settle after the first few doses
- ■Signs of an allergic reaction such as hives, swelling or trouble breathing
- ■You are diagnosed with cancer or begin cancer treatment
- ■You will be drug tested for sport, since it is prohibited and widely screened for
Community poll
Self-reported by visitors. Not clinical evidence.TB-500: frequently asked
What is the difference between TB-500 and thymosin beta-4?
Thymosin beta-4 is the full 43 amino acid natural protein. TB-500 is a marketing name that usually refers to a synthetic 7 amino acid fragment (LKKTETQ) taken from the actin-binding region. The fragment is cheaper to make and is what most research vendors sell, although some ship the full protein under the same label.
Why is the dose so much higher than BPC-157?
TB-500 is dosed in milligrams rather than micrograms because animal studies used higher weight-based doses and because it works systemically rather than at a concentrated local site. The two peptides are not comparable on a per-milligram basis.
Do I need a loading phase?
The loading protocol is a community convention, not something derived from a human trial. The idea is to reach tissue saturation quickly and then maintain it. Many people skip loading and simply dose 2 to 2.5 mg twice weekly for the duration of their cycle.
Can it help with hair growth?
Mouse studies showed thymosin beta-4 promoted hair growth by activating follicle stem cells. There are no human trials for this purpose. Some people report thicker hair as a side benefit, but it is not a reliable primary use.
References
- Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature, 2004
- Thymosin beta 4 accelerates wound healing. Journal of Investigative Dermatology, 1999
- Thymosin beta4 promotes hair growth via activation of follicle stem cells. FASEB Journal, 2004
- Thymosin beta 4 in dry eye and neurotrophic keratopathy, phase 2 clinical results. RegeneRx clinical program, 2015