Healing and Recoveryinjurymuscletendoncardiacflexibility

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.

Status
Investigational, not FDA approved. Prohibited by WADA for athletes.
Reported dose
2 to 5 mg
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.
Frequency
Twice weekly during loading, then weekly or every other week
4-6 week loading phase, then maintenance or stop and reassess
Route
Subcutaneous, Intramuscular
Half-life
Roughly 1-2 hours in plasma (estimated); the full protein persists longer in tissue

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.

What the research shows

  • 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.

Evidence labels: 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.

Dose calculator

U-100 insulin syringe
Draw
- units
- mL at -
- doses per vial. - per unit.

Units 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.

Dosing and protocol

Reported range
2 to 5 mg per dose

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.

Frequency
Twice weekly during loading, then weekly or every other week

4-6 week loading phase, then maintenance or stop and reassess

Timing

Injection site does not need to be near the injury. Subcutaneous in the abdomen is most common.

Common vial sizes and reconstitution
VialSuggested waterConcentrationLow dose draw
5 mg1 mL5 mg/mL40 units
10 mg1 mL10 mg/mL20 units
Storage

Lyophilized: freezer or fridge, away from light. Reconstituted: fridge 2-8C, use within 4 weeks.

Cautions

  • ▲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.

Commonly stacked with

BPC-157

The most common recovery stack. BPC-157 is applied locally for tendon and gut repair while TB-500 works systemically on cell migration and inflammation.

GHK-Cu

Adds collagen synthesis and skin remodeling for surgical or wound recovery.

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

  1. Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair. Nature, 2004
  2. Thymosin beta 4 accelerates wound healing. Journal of Investigative Dermatology, 1999
  3. Thymosin beta4 promotes hair growth via activation of follicle stem cells. FASEB Journal, 2004
  4. Thymosin beta 4 in dry eye and neurotrophic keratopathy, phase 2 clinical results. RegeneRx clinical program, 2015
Educational only. Dose ranges describe what appears in published research and community protocols. This is not medical advice and most of these compounds are not approved for human use. Talk to a clinician who knows your history.