TB-500 is not an approved medicine anywhere, and no regulator, product label, or completed clinical trial defines a human dose. The figures below document what is reported in marketing material, community logs, and animal studies. They are context for reading those sources, not a protocol to follow.
The short answer
There is no established TB-500 dose. The number most often repeated online — roughly 2–2.5 mg twice weekly for four to six weeks, then a weekly or fortnightly maintenance dose — is a community convention with no pharmacokinetic basis behind it. The only dosing schedule that appears in a regulator-documented source is the one that was marketed for horses: a 10 mg vial weekly for six weeks, then monthly (RMTC Thymosin β4 Bulletin). Human dose-finding for this fragment is happening for the first time now, in a trial that began in 2026 (NCT07487363).
The protocols that actually circulate
1. The marketed equine schedule. The Racing Medication and Testing Consortium documented the protocol supplied with TB-500 products sold for horses: subcutaneous injection of the contents of one 10 mg vial once weekly for six weeks, then monthly indefinitely, with a recommendation to administer the day after an intense workout. Product cost was recorded at $150–300 per 10 mg (RMTC).
2. The human community pattern. Logs and forum posts consistently describe a "loading" phase of about 2–2.5 mg twice weekly for four to six weeks, followed by maintenance at a similar per-injection amount once weekly or every other week. This pattern has no published source; it is convention transmitted between users.
3. Animal study doses. Preclinical work uses weight-based dosing — for instance 60 µg/kg/day intraperitoneally for four weeks in a rat Achilles-tendon repair model, which produced significantly higher load to failure than controls (Biçer et al., Jt Dis Relat Surg 2026). Scaling a rodent intraperitoneal milligram-per-kilogram figure to a human subcutaneous weekly dose is not a calculation anyone has validated.
Notice that these three sources disagree by an order of magnitude and were never reconciled. The community figure is not a scaled-down version of the equine one, nor an allometric conversion of the rodent one — they are independent conventions.
What is known about pharmacokinetics
Essentially nothing, for the fragment, in humans. No published study reports its absorption, distribution, half-life, or clearance after subcutaneous administration. The 2026 phase 1/2 study lists pharmacokinetics among its objectives in a randomized, double-blind, placebo-controlled, sequential dose-escalation design in 80 adults with stable atherosclerotic cardiovascular disease (NCT07487363) — which is a plain admission that these numbers do not yet exist.
Data on the full-length parent protein does not fill the gap. Thymosin beta-4 is a 43-amino-acid protein with its own handling in the body, including an N-terminal fragment (Ac-SDKP) released enzymatically by meprin-α and prolyl oligopeptidase (Kumar et al., Am J Physiol Renal Physiol 2016) — chemistry a peptide starting at residue 17 cannot reproduce.
Concentration versus dose
TB-500 is supplied as a lyophilized powder that must be reconstituted before it can be measured out at all. Two ideas do most of the damage when they are confused:
Diluent volume sets concentration, not dose. The same vial reconstituted with 1 mL or 5 mL contains the same total peptide at five-fold different concentrations.
Syringe "units" measure volume. An insulin syringe reads in units of volume, so a unit corresponds to a milligram amount only once concentration is fixed. This is the single most common source of order-of-magnitude errors in peptide arithmetic.
Why the numbers are unreliable even if followed exactly
All of the above assumes the vial contains what the label claims. Testing commissioned by racing regulators found that many TB-500-labeled products contained no thymosin beta-4 or derived peptide, and that most contained no proteins, peptides, or amino acids at all; one sample was confirmed as N-acetylated LKKTETQ (RMTC). When the identity of the material is unverified, precision in the arithmetic is precision about an unknown quantity.
Why oversight matters
For an approved medicine, a dose comes bundled with an indication, contraindications, interaction warnings, monitoring requirements, and a manufacturer legally responsible for the contents. TB-500 has none of those. It is additionally prohibited in sport at all times under category S2.3 of the WADA Prohibited List, so for tested athletes the schedule question is moot.
For the mechanism and evidence behind these compounds, see the main TB-500 page, the side effects and safety page, and what are the risks of peptides.
Sport & Anti-Doping Warning
TB-500 (a thymosin beta-4 fragment) is classified as a prohibited peptide hormone/growth factor and has appeared in elite-sport doping investigations, including endurance running cases where it was used alongside EPO and other banned agents.
- >Overview of peptide hormones and growth factors on the WADA Prohibited List (S2)
- >Reporting on TB-500 and other experimental peptides in performance contexts
Use of TB-500 by athletes governed by anti-doping rules is generally treated as a serious violation, particularly when combined with other anabolic or blood-boosting drugs.