Where TB-500 Is Injected: Routes, Sites and the Record

"Where to inject TB-500" asks for a fact that no regulator has written down. TB-500 has no label, the human injection study behind its reputation used a different molecule by a different route, and the one registry entry that names it turns out, on reading, to describe itself as fictional. What does exist is two animal studies that state the route they used, clinic pages that state the site they use, and a widely repeated claim about injecting close to an injury. This page sets out each source as it stands (all opened 2026-10-17) and converts the circulating amounts into syringe units. It describes; it recommends no amount, route or site.

The figures themselves, with their sources, are on the TB-500 dosage page; the same question for its usual partner is answered on how BPC-157 is injected, and the general technique on how peptides are injected.

What the record holds, by source

The top two rows are the human record, and neither answers the question: one is a different molecule given into a vein, the other has no route at all. The animal rows state a route, and both put the compound into the abdominal cavity. The clinic rows are practice descriptions and disagree with each other about what can be said.

The registry record, read to the end

NCT07487363 is listed as recruiting, with 80 adults with stable atherosclerotic disease in three dose arms against a matching vehicle; this site's dosage page, read on 2026-09-18, reported it as the only registration naming TB-500. Its brief summary, read in full on 2026-10-17, opens: "This fictional study is an example of a ClinicalTrials.gov-style record." It names no milligram figure, no route and no site. Its sponsor posted eight records between 2026-02-27 and 2026-04-01, one of them titled "Mock Study". ClinicalTrials.gov lists what sponsors submit; it does not verify it, and this record should not be read as a trial.

The "inject near the injury" claim

The idea that TB-500 works better when injected close to a damaged tendon or muscle is common on forum and clinic pages, and some pages describe the opposite — that the compound travels through the body so the site does not matter. Neither statement rests on a comparison. What the two animal studies show is narrower: in both, the compound was given into the abdominal cavity, not at the injury, and an effect was reported at the injury.

• Skin wounds, 1999. Rats with full-thickness wounds received thymosin beta-4 either on the wound or intraperitoneally; both increased re-epithelialisation, by 42% over saline at day 4 and up to 61% at day 7, with more collagen and new vessels in the treated wounds.
• Achilles tendon, 2026. Thirty-two rats had the tendon cut and repaired; eight received TB-500 at 60 µg/kg a day intraperitoneally for four weeks. That group had a significantly higher maximum load to failure than controls and better histology scores. A BPC-157 group and a combined group were also run; the combination added nothing over either alone.

Neither study included an arm injected at the injury, so neither shows that location makes no difference — only that a distant route was enough for the effect each measured in rats. The same gap is set out for BPC-157, where the "near the injury" claim is stronger, on the BPC-157 injection page; how the two compounds compare in dose is on BPC-157 vs TB-500.

Subcutaneous or intramuscular

The clinic page that ranks highest for the question names subcutaneous injection into the abdominal fat as the most common route and intramuscular injection into a muscle belly as an alternative, saying intramuscular is "sometimes preferred" for faster absorption. No study of the fragment measured absorption by either route, so that rationale is the clinic's own. The dermatology page takes the opposite position: there is "insufficient evidence" to prefer either route for recovery use, and evidence about full-length thymosin beta-4 "cannot automatically be applied" to the fragment. Both are reported here as written.

The amounts, as syringe units

Units on a U-100 syringe = milligrams ÷ concentration in mg/mL × 100. The amounts in circulation are 2 to 2.5 mg per injection, twice a week for four to six weeks and then weekly or fortnightly (vendor, clinic and forum pages, recorded on this site's dosage page, 2026-09-18). Research vials are labelled 5 mg and 10 mg.

Where the concentrations come from: 10 mg/mL is a 10 mg vial with 1 mL of water; 5 mg/mL a 5 mg vial with 1 mL or a 10 mg vial with 2 mL; 3.33 mg/mL a 10 mg vial with 3 mL; 2.5 mg/mL a 5 mg vial with 2 mL. Because the circulating figures are whole milligrams, TB-500 draws are large by this site's standards — 40 to 100 units — and more water quickly pushes a single amount past one syringe. That is the practical constraint behind the intramuscular-volume question; a subcutaneous injection of 1 mL is at the upper end of what clinic pages describe for any peptide. The TB-500 vial arithmetic works any vial and volume, and mg to units gives the method.

Status that bears on the injection

The 2026 World Anti-Doping Agency Prohibited List names "Thymosin-β4 and its derivatives e.g. TB-500" in section S2.3, growth factors and growth factor modulators, prohibited at all times (Tractatenblad 2026 no. 25, read 2026-10-17). The FDA's advisory committee vote of 2026-07-23 on TB-500 for compounding, and the agency's earlier Category 2 placement, are recorded with dates on the TB-500 dosage page; the vote is advisory and established no dose or route. A 2026 review in Missouri Medicine groups TB-500 with BPC-157 and melanotan II among unregulated injectables that "lack established human safety profiles", naming contamination, impurities and inaccurate dosing among the risks (PMID 42757290, abstract read 2026-10-17).

What is not established

No label, so no regulator's statement of a route or site. No human study of the fragment by any route. No comparison of injection sites, or of injecting at an injury with injecting elsewhere, in any species. No absorption data for subcutaneous against intramuscular injection. The circulating amounts trace to no published source. Medibact's TB-500 guide covers the compound. Decisions about whether and how to use it belong with a clinician.

Sources and dates

Opened 2026-10-17: PubMed abstracts through NCBI E-utilities for PMIDs 20536472, 10469335, 42542926 and 42757290, and the PubMed count for "TB-500" or "TB500" in title or abstract (34 records); ClinicalTrials.gov v2 API record NCT07487363 (summary, arms, interventions) and searches for TB-500 (1 record) and thymosin beta 4 subcutaneous (0); the Perfect B TB-500 protocol page (updated 2026-10-13) and the Natura Dermatology TB-500 injection page (2026-04-28); the 2026 Prohibited List text in Tractatenblad 2026 no. 25. From this site's dosage page (opened 2026-09-18): the circulating figures and the FDA and advisory-committee dates. Unit arithmetic by this site. Corrections go to the contact page.