TB-500 Dosage Chart: Loading and Maintenance Phases Used in Studies

Key takeaways

• There is no TB-500 dosage from any study, because there are no studies: FDA's July 2026 review found no article in which TB-500 was administered to a human, for any condition, by any route, and no animal toxicology of any kind.
• The loading and maintenance chart sellers circulate, 2 to 2.5 mg twice weekly for four to six weeks and then 2 to 5 mg monthly, is a vendor convention copied between forums since the horse-racing days. It cannot be traced to any experiment.
• Every dose that has actually appeared in research belongs to something else: full-length thymosin beta-4, a different 43-amino-acid molecule, in human trials of eye drops, gels and infusions; 60 mcg/kg daily in one rat tendon study; and a single 10 mg shot in a horse doping study.
• TB-500 as FDA evaluated it is a seven-amino-acid fragment of thymosin beta-4 (Ac-LKKTETQ), in free-base and acetate forms. Any future compounding rule would cover those molecules, not full thymosin beta-4, which as a 43-amino-acid protein is a biological product no pharmacy may compound at all.
• No US pharmacy may compound TB-500 as of October 2026, so there is no pharmacy label to dose from. This page publishes no reconstitution example and no units table, because there is nothing legitimate for that arithmetic to describe.

There is no TB-500 dosage used in studies, because TB-500 has never been studied in a human being: FDA searched the medical literature for its July 2026 advisory review and found no article in which TB-500 was administered to a person, for any condition (FDA briefing 2026). The loading and maintenance phases on seller charts are vendor conventions, and the doses that did appear in research belong to a different molecule or a different species. This page separates the two, as part of our tendon and joint healing evidence review; the companion BPC-157 dosage chart does the same for the other half of the so-called Wolverine stack.

The chart sellers circulate, labeled as what it is

What circulates online, on vendor pages, forums and clinic handouts, almost always has this shape:

These figures are reproduced so you can recognize them, not so you can follow them. They appear to have been copied from forum to forum since TB-500's days as a veterinary product in horse racing, and they do not even match the animal data: scale the one rat study's dose to a 70 kg adult by body weight and you get roughly 4 mg every day; scale it by body surface area and you get under 1 mg a day. Neither resembles 2.5 mg twice a week. A chart whose numbers trace to nothing is not a dosage chart; it is marketing with units attached. The 2023 laboratory analysis of TB500 products bought online adds the final problem: their contents were not consistently what the descriptions claimed (Delcourt 2023), so even a buyer determined to follow the chart cannot know what milligrams they are actually measuring.

What was actually dosed in studies

Two details deserve emphasis. First, the safety figure sellers borrow, 1,260 mg tolerated intravenously, belongs to the full-length protein, made to pharmaceutical standards and infused under monitoring; a seven-amino-acid fragment with a different sequence, metabolism and immune profile does not inherit that record. Second, FDA's reviewers could not find even animal toxicology: no acute, repeat-dose, genotoxicity, reproductive or carcinogenicity studies of TB-500 in either form (FDA briefing 2026). The 2026 rat tendon experiment, published around the time of the meeting, is the entire in-vivo efficacy record for the substance people inject.

Which molecule is TB-500? What FDA evaluated

TB-500 is a product name, and FDA's briefing document for the July 23, 2026 meeting is the most precise statement so far of what sits behind it. FDA evaluated two bulk drug substances: TB-500 free base, a seven-amino-acid synthetic fragment of thymosin beta-4 covering amino acids 17 to 23 with an acetyl group on the N-terminal leucine (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH, molecular weight 889), and TB-500 acetate, its acetate salt. The evaluated use was wound healing, and the nominated product was a 3 mg/mL powder for subcutaneous or intramuscular injection. The document notes that websites use TB-500 and thymosin beta-4 interchangeably although they are not the same substance, that FDA has encountered multiple salts and even different active moieties sold under the one name, and that the nomination package itself was inconsistent, naming the free base while attaching a certificate of analysis for the acetate (FDA briefing 2026). The committee voted 8-6-1 to recommend both forms anyway (HPM 2026).

The identity question has a legal edge worth knowing before anyone tells you compounded TB-500 is coming. If FDA ever finalizes a rule from that vote, it would cover the substances FDA evaluated, the seven-amino-acid fragment as free base and acetate. It could not cover full-length thymosin beta-4: at 43 amino acids, that molecule is over the 40-amino-acid threshold at which federal law classifies a chain as a protein and regulates it as a biological product, and biological products cannot be compounded under 503A or 503B at all, as the legal tracker explains. Since some vials sold as TB-500 have been found to contain the full-length protein rather than the fragment (Delcourt 2023), part of the TB-500 market is selling a substance with no possible compounding future under any rule.

How long it lasts, as far as animals can say

Nothing about duration of action is known in humans, but the animal pharmacokinetics undercut the monthly-maintenance idea. In horses given a single 10 mg subcutaneous dose, the fragment was identified in plasma and urine, with FDA's summary of the study noting plasma concentrations peaked between one and two hours and fell below quantifiable levels within six to ten hours (Ho 2012); (FDA briefing 2026). In rats, the peptide is cut down from the C-terminal end into smaller acetylated fragments, with Ac-LKK detectable for up to 72 hours; notably, in a cell wound-healing assay the parent TB-500 did nothing, while one metabolite, Ac-LKKTE, produced a small but significant effect (Rahaman 2024). A molecule cleared within hours, whose own activity in vitro may belong to a breakdown product, is a strange candidate for a once-a-month maintenance dose; the schedule was invented for commerce, not pharmacology. The fragment was first characterized by doping-control chemists (Esposito 2012), and those laboratories test for it and its metabolites, so for tested athletes the relevant window is detection, not effect: TB-500 is named on the 2026 WADA Prohibited List under S2 and banned at all times (WADA 2026).

Why there is no reconstitution math on this page

Our reconstitution calculator exists for products a licensed pharmacy can dispense, where a label states the milligrams and a prescriber sets the dose, and the arithmetic has something real to check against. TB-500 has none of that: no approved product anywhere, no US pharmacy permitted to compound it as of October 2026, no established human dose, and vial contents that vary by vendor. Publishing a water volume or a syringe-units table for it would dress a vendor claim as an instruction, so we do not. If the vote becomes a final rule, the legal tracker will record it the day it happens, and this page will be updated with whatever a pharmacy label then actually says.

Bottom line

A TB-500 dosage chart is a chart of claims. The loading and maintenance phases were used in no study; the studied doses belong to full-length thymosin beta-4, to rats and to a horse; and FDA, reviewing the substance in 2026, found no human study and no animal toxicology at all. The molecule itself is a seven-amino-acid fragment whose commercial versions do not reliably contain what the label says. If you are dosing TB-500, you are following a forum, not a study, with a product no one has checked, and the profile and joint-healing evidence review explain what has actual evidence for the injury that sent you here.

Frequently asked questions

+−What is the correct TB-500 dosage?

There is none. No human study of TB-500 has ever been conducted, by any route, at any dose, a fact FDA stated in its July 2026 review, so no correct, safe or effective dose exists. The numbers on seller charts, usually 2 to 2.5 mg twice a week and then monthly, were written by vendors and copied between forums; none traces to a study of any kind.

+−What is the TB-500 loading and maintenance protocol?

A seller convention, not a protocol. The structure, a loading phase of 2 to 2.5 mg twice weekly for four to six weeks followed by 2 to 5 mg once or twice a month as maintenance, appears on vendor sites and forums and has never been used in any study, human or animal. The only animal efficacy study used daily injections for four weeks at a weight-based dose that does not convert to any of those numbers.

+−How many mg of TB-500 per week was used in studies?

In humans, zero, because there are no human studies of TB-500. The one animal efficacy study gave rats 60 mcg per kilogram into the abdomen every day for four weeks. The large doses sometimes quoted for safety, up to 1,260 mg intravenously, were doses of full-length thymosin beta-4, a different, 43-amino-acid molecule, in a pharmaceutical Phase 1 trial, and say nothing about the fragment in a TB-500 vial.

+−Which molecule did FDA actually evaluate as TB-500?

A seven-amino-acid synthetic fragment of thymosin beta-4, amino acids 17 to 23 with an N-terminal acetyl group (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH), in two forms, the free base and the acetate salt. FDA's 2026 briefing document treats them as different bulk drug substances, notes that websites wrongly use TB-500 and thymosin beta-4 interchangeably, and records that the nomination paperwork itself mixed the two forms up.

+−How long does TB-500 stay in your system?

The only data are from animals. In horses given a single 10 mg subcutaneous dose, plasma levels peaked within one to two hours and were unquantifiable within six to ten hours; in rats, a breakdown product, acetylated LKK, remained detectable for up to 72 hours. Anti-doping laboratories test for the fragment and its metabolites, so athletes should assume a much longer detection window than the duration of any claimed effect.

+−Can a doctor prescribe TB-500 for an injury?

A clinician can write anything, but no licensed US pharmacy may compound or dispense TB-500 as of October 2026, so the prescription cannot be legally filled. FDA's advisory committee voted 8-6-1 in July 2026 to recommend it despite FDA finding no human studies, and no rule has been published. A clinic selling TB-500 injections is supplying a research vial whose contents vary by vendor.

+−Is there a TB-500 dose for muscle growth or recovery?

No. No human study has measured muscle, recovery or performance outcomes on TB-500 at any dose, and the compound is named on the WADA Prohibited List under S2, banned at all times in tested sport. Seller dosing for these goals is the same untraceable loading-and-maintenance chart relabeled.

Sources

1. RegulatoryFDA. Briefing document, Pharmacy Compounding Advisory Committee meeting of July 23-24, 2026: FDA evaluation of TB-500-related bulk drug substances (TB-500 (free base) and TB-500 acetate), dated May 15, 2026. (2026)
2. StudyEsposito S et al. Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential. Drug Test Anal 2012;4:733-8. (2012)
3. StudyHo EN et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta-4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A 2012;1265:57-69. (2012)
4. StudyRahaman KA et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. J Chromatogr B 2024;1235:124033. (2024)
5. StudyBicer O et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: a histopathological and biomechanical study. Jt Dis Relat Surg 2026;37:822-37. (2026)
6. StudyRuff D, Crockford D, Girardi G, Zhang Y. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci 2010;1194:223-9. (2010)
7. StudyDelcourt V et al. TB500/TB1000 and SGF1000: a scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal 2023;15:458-64. (2023)
8. NewsPalmer KL, Snow CD, Bass M. PCAC approves four bulk drug substances for the 503A list (BPC-157, KPV, TB-500, MOTS-c). FDA Law Blog, Hyman Phelps & McNamara, July 24, 2026. (2026)
9. RegulatoryWorld Anti-Doping Agency. The 2026 Prohibited List (in force January 1, 2026): S2.3 growth factors and growth factor modulators names thymosin-beta 4 and its derivatives, e.g. TB-500. (2026)