TB-500 dosage, as the studies actually administered it — in species, by route, at stated amounts.

TB-500 Dosage Ranges Reported in the Research Literature

TB-500 dosage is reported here strictly as what was administered to which species, by which route, at which amount — never as a human recommendation. And almost all of it is full-length thymosin beta-4, not the 7-mer.

Animal studies span a wide range. Cardiac and neurological rodent models have used roughly 6-12 mg/kg; the rat embolic-stroke dose-response used 2, 12, and 18 mg/kg intraperitoneally, with a modeled optimum near ~3.75 mg/kg and no benefit at the top dose ^[4]. A long-running muscular-dystrophy (mdx) mouse study used 150 µg twice weekly intraperitoneally for six months. In vitro, picogram-to-nanogram amounts are bioactive — ~10 pg was active in keratinocyte migration assays ^[3]. The spread is enormous because the route, the model, and the readout all differ; there is no single "research dose" of thymosin beta-4, let alone of TB-500.

The one human dataset: Phase 1 intravenous

Human dosing data exist only for full-length thymosin beta-4. In a randomized, placebo-controlled Phase 1 study, synthetic thymosin beta-4 was given intravenously to 40 healthy volunteers — four cohorts of ten — as a single dose then daily for 14 days at 42, 140, 420, or 1260 mg. It was well tolerated to the top dose, with only infrequent mild or moderate adverse events and no dose-limiting toxicities or serious adverse events ^[6].

Two things to hold onto. The amounts are in milligrams by intravenous infusion under trial supervision — a different world from the subcutaneous community use TB-500 is associated with. And, again, the molecule was the full-length protein, not the Ac-LKKTETQ fragment.

Routes studied

The routes in the literature are, predominantly, intraperitoneal in rodent efficacy studies; intravenous in the human Phase 1 and some cardiac models ^[6]; and topical or ophthalmic in corneal and dermal wound work and the dry-eye trials of RGN-259 ^[9]. Subcutaneous and intramuscular routes appear in community research use, but those are not the routes of controlled human efficacy trials.

As supplied, TB-500 is a lyophilized powder reconstituted in bacteriostatic or sterile water and kept refrigerated. As a short acetylated peptide it is more chemically robust than the full-length protein, but it remains subject to proteolysis and freeze-thaw degradation — and the identity and purity of research-grade material is a recurring, unresolved concern ^[10].

Why community loading protocols have no controlled-trial basis

The "load high for a few weeks, then maintain" protocols that circulate in athletic and peptide-research communities are not derived from controlled human trials and have no published clinical validation ^[10]. The stroke data argue directly against the premise: more was not better — 18 mg/kg underperformed 12 mg/kg in the dose-response ^[4]. A non-monotonic curve is the worst possible backdrop for an open-ended loading strategy, and there is no human pharmacokinetic anchor to calibrate against.

TB-500 Half-Life and Pharmacokinetics

There is no validated human pharmacokinetic half-life for the TB-500 heptapeptide ^[10]. In the intravenous full-length thymosin beta-4 Phase 1 study, pharmacokinetics were dose-proportional and the half-life increased with dose ^[6]. Separately, anti-doping LC-MS work has characterized TB-500 and its metabolites — in equine plasma and urine, and in vitro — for detection, not for human PK ^[10].

So the honest summary is short. Dose-dependent, dose-proportional PK is documented for the full-length protein given intravenously; nothing equivalent is published for the fragment in humans. Detectability has been worked out for anti-doping purposes; a clean human clearance window for TB-500 has not. For where that detection science came from — racehorses — and what it means for sport, see TB-500 WADA anti-doping status.

Form, stability, and why material identity complicates every dose

Dose is only as meaningful as the molecule behind it, and that is a live problem for TB-500. Research-grade material is supplied as a lyophilized powder, reconstituted in bacteriostatic or sterile water and kept refrigerated. As a short acetylated peptide, Ac-LKKTETQ is more chemically robust than the full-length protein, but it remains subject to proteolysis and freeze-thaw degradation — so handling matters to whatever the label claims.

The deeper issue is identity. In unregulated supply, the peptide's purity and correct sequence are not guaranteed, and a recurring concern across the literature is whether a vial sold as "TB-500" contains the heptapeptide, the full-length protein, a different fragment, or a degraded mixture ^[10]. That ambiguity does two things at once: it makes any stated research dose hard to interpret, and it muddies the anecdotal reports that circulate alongside the science. A figure like 2 mg/kg only means something if the substance dosed is actually what it says on the vial — which is exactly the assurance the framework on TB-500 legal status and FDA 503A category is built to provide, and which research-grade supply does not.