TB-500

What it is

TB-500 is a lab-made, shortened version of Thymosin Beta-4 (Tb4), a small protein the body already makes. TB-500 is not the whole protein - it is a synthetic 7-amino-acid snippet (Ac-LKKTETQ) built to match the actin-binding region of Tb4. By binding actin, the internal scaffolding of cells, it is thought to help cells change shape and migrate to injury sites. In animal studies, Tb4 sped wound closure, grew new blood vessels, and drew muscle-repair cells to injured tissue. Human clinical trials exist only for the full molecule (an IV safety study, and eye drops for dry eye) - not for the injected TB-500 fragment. The popular milligram-dose, twice-weekly protocol comes entirely from online communities and vendors, not from published research. Treat it as unproven self-use, not an established medical dose.

Dose ranges

Study-backed ranges carry a source you can open. Community ranges are widely reported but not clinically established - treat them as what people do, not as advice.

Reconstitution & storage

5 mg is the vial size that shows up consistently in community guides. 1 mL bacteriostatic water gives 5 mg/mL, 2 mL gives 2.5 mg/mL. None of this comes from a clinical or manufacturer monograph - it is vendor and community convention.

Common stacks

Interactions & cautions

No formal human drug-interaction studies exist for TB-500 or injected Thymosin Beta-4, so nothing here is clinically confirmed. Mechanism-based cautions: avoid with active cancer or a cancer history (Tb4 promotes blood-vessel growth, which could in theory feed tumors), and avoid in pregnancy or breastfeeding (unstudied). TB-500 and Tb4 derivatives are on the WADA prohibited list. The FDA lists the TB-500 fragment (sequence LKKTETQ) among bulk substances with safety data too limited for compounding. The biggest practical risk is often the unregulated product itself - contamination, mislabeling, or wrong concentration.

Questions people ask

Sources

1. [1]Biodistribution of synthetic thymosin beta 4 in the serum, urine, and major organs of mice PMID 9226473studyIn mice given thymosin beta-4 IP, serum rose within 2 minutes and cleared within about 40 minutes via rapid renal excretion.
2. [2]Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues PMID 16099219studyThymosin beta-4 is the major actin-sequestering peptide in cells, underlying its role in wound healing and tissue repair.
3. [3]Muscle injury-induced thymosin beta4 acts as a chemoattractant for myoblasts PMID 20880960studyAfter muscle injury in mice, locally produced thymosin beta-4 attracted myoblasts to the injury site and accelerated their migration.
4. [4]A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers PMID 20536472studyIV thymosin beta-4 at 42-1260 mg was well tolerated in healthy humans with dose-proportional pharmacokinetics and half-life increasing at higher doses.
5. [5]Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled Phase II trial PMID 26056426study0.1% thymosin beta-4 eye drops produced statistically significant improvement in corneal staining in dry-eye patients versus vehicle.
6. [6]Thymosin Beta-4 and TB-500 in Tissue Healing: A Scoping Review (2026)studyHuman evidence exists for whole Thymosin Beta-4 in ocular and wound settings; direct human evidence for the TB-500 fragment was limited to a single non-musculoskeletal study. Notes FDA lists LKKTETQ as a bulk substance of concern and WADA prohibits TB4/TB-500.
7. [7]TB-500 & BPC-157 Stacking: Dosing Protocols (community guide)communityCommunity guide reporting a 5 mg TB-500 vial with 1 mL bacteriostatic water, dosed ~2-2.5 mg 1-2x weekly; states outright that no human dosing or PK study supports these numbers.