The TB-500 dosage question has an answer, and it fits in one sentence: no human dose of TB-500 has been set by any published study, because no study has given TB-500 to a person. That is the finding inside the Food and Drug Administration’s own review, and it explains why four figures travel as a TB-500 dosage while not one of them came from a human being.
We will not hand anyone a number to draw into a syringe. Doses vary by patient and by prescriber, and that decision belongs to a licensed clinician who has examined the person in front of them. Here is what the record holds, because a clinic quoting a TB-500 dosage to a stranger is quoting something.
TB-500 dosage: the answer in FDA’s own review
FDA evaluated the compound twice, as the free base and as the acetate salt, because the pharmacy nomination could not say which of the two it meant. Its memo to the Pharmacy Compounding Advisory Committee, dated May 15, 2026, covered searches of PubMed, Embase, ClinicalTrials.gov, DailyMed, Drugs@FDA, the European and Japanese Pharmacopoeias and the agency’s adverse-event files.
That search turned up no article in which TB-500 had been given to a human. A later section closes the door from the other side: FDA did not identify clinical studies in humans assessing the pharmacokinetics or pharmacodynamics of either form by any route. No absorption measurement, no clearance measurement, no half-life, in a person. A dosing schedule needs one of the three, and the three remain unmeasured.
This is not a gap in data about an obscure compound. FDA found websites selling TB-500, one publishing reconstitution and administration instructions, and a 2016 forensic study of 13 bodybuilding forums where TB-500 ranked among the two most discussed substances. The talk is abundant. The measurements are missing.
The numbers in circulation, and where each one came from
The first is 3 mg/mL, the strength of the product proposed in the withdrawn pharmacy nomination: a lyophilized powder for subcutaneous or intramuscular injection. That is a concentration, listed for a product that was not studied in anyone.
The second is 10 mg, and that one is a dose, given once, to horses. Ho and colleagues gave thoroughbred geldings a single 10 mg subcutaneous dose: plasma concentrations peaked at 0.05 and 0.08 ng/mL between 60 and 120 minutes, then fell until the assay could no longer quantify the peptide between 6 and 10 hours. That study exists to catch doping in racing animals, and it tells a person with a torn rotator cuff nothing about themselves.
The third is 50 mg/kg given intraperitoneally to rats, an experiment built to identify metabolites in urine.
The fourth figure has no published source at all. The 2 mg to 2.5 mg twice-weekly schedules on vendor pages trace back to product listings. FDA logged vials of 2 mg, 3 mg, 5 mg, 10 mg and 15 mg of powder for reconstitution, sold as research use only. A vial size is how much solid sits in a bottle. It carries no route, no frequency and no duration.
A strength is not a dose, and a vial is not a schedule
Strength is how much drug sits in a given volume. Dose is how much reaches a patient in one administration. Schedule is how often. A page can quote a strength and sound like it quoted a dose, leaving the reader with a number and no route attached.
The animal work shows how carefully the line needs drawing. In the mouse study FDA reviewed, researchers made four 3 mm punch wounds on the backs of 26-month-old female mice and applied 50 microliters of the non-acetylated heptapeptide at 0.01% topically that day and again 48 hours later. That peptide is not TB-500. TB-500 carries an acetyl group on its N-terminal leucine, and FDA’s memo states that acetylation “irreversibly alters their charge, hydrophobicity, and size,” so the pharmacology of the unacetylated fragment “cannot be directly extrapolated.” FDA also noted the study “lacks an assessment of the dose-response relationship.”
Then there is the dish. Rahaman and colleagues incubated cultured fibroblasts with scratch wounds for eight hours in TB-500 at 50 micrograms per milliliter. Wound closure did not differ from the vehicle control. FDA’s summary is blunt: TB-500 (free base) “appeared to be devoid of wound-healing properties in an in-vitro study.” The metabolite N-acetylated LKKTE produced a small but significant closure at the same concentration, which leaves open whether the peptide sold as TB-500 is the active molecule or a precursor to one. The strongest laboratory result in this file belongs to a breakdown product, not the peptide on the vial.
Tendon, muscle and recovery: no human data on either molecule
TB-500 is a seven amino acid fragment, residues 17 through 23 of thymosin beta-4, acetylated at the N-terminus. Thymosin beta-4 is the full 43 amino acid protein. FDA states that “thymosin beta-4 and TB-500 are not the same substance,” and that sentence does more work than any other in this file.
The human studies cited in TB-500 marketing used the parent protein, mostly in eye and skin research, and none studied tendons, muscle or athletic recovery in people. FDA checked the references the pharmacy nomination submitted and found all three were studies of thymosin beta-4. For the fragment itself, the memo reports no human administration, no human pharmacokinetic data and no human musculoskeletal data.
The athletic reputation came from somewhere else. FDA records that a veterinary preparation appeared in 2011 and was marketed to boost performance in equine and greyhound sports, and that the World Anti-Doping Agency lists TB-500 under section S2.3 of its prohibited list. A compound that reaches the public through racing stables and bodybuilding forums, with no clinical program behind it, arrives with a reputation instead of a dose.
An empty safety file is not a clean safety file
FDA recorded an absence in each category it checked: no acute toxicity studies, no repeat-dose toxicity studies, no genotoxicity studies, no developmental and reproductive toxicity studies, no carcinogenicity studies, and no studies of the immunogenicity or aggregation of either form.
The immunogenicity point drew the agency’s sharpest language. Peptides given by injection can provoke an immune response, and the risk rises with aggregation and with peptide-related impurities. FDA wrote that it remains “particularly concerned about the absence of human data on drug products containing these substances administered via any route of administration,” and that potential safety risks in humans are unknown.
The adverse-event files are thin for a reason worth understanding. FDA searched its reporting system for TB-500 reports through March 26, 2025 and retrieved none, and a search of the supplement complaint system from January 1, 2004 to March 10, 2025 returned two cases involving “blended TB-500 and BPC-157,” neither carrying a safety assessment. Reporting is voluntary, and FDA states it cannot draw definitive conclusions from those systems. A quiet database where reports are rare is what a researcher expects, not a safety finding.
None of this makes TB-500 a poison, and none of it makes it a treatment. It makes it unmeasured. The current text of 21 CFR 216.23 lists six bulk drug substances for 503A compounding and TB-500 is not among them, and FDA’s own reviewers proposed against adding it. An advisory recommendation does not amend a regulation, which our breakdown of the July 2026 committee meeting explains, and the TB-500 compound page tracks the status as it changes.
Questions to put to a clinic quoting a TB-500 dosage
A clinic that will talk about this compound on the record can answer six questions.
First, which molecule is in the vial: the acetylated seven amino acid fragment, or thymosin beta-4 under a borrowed name? FDA found multiple salts, derivatives and different active moieties sold under the TB-500 name, and noted that inconsistent naming is itself a patient safety risk.
Second, which human study supports the number being quoted? If the answer names a trial, ask for the year and the dose. If it names a horse study, a forum thread or a supplier page, the number is a suggestion.
Third, is the figure a strength or a dose? Milligrams per milliliter describes the bottle. Milligrams per administration describes the patient.
Fourth, who holds the prescription and who compounds the product? Compounded drugs are not FDA-approved, and FDA does not verify their safety, effectiveness or quality before they reach a patient.
Fifth, can the clinic produce a certificate of analysis for the lot, showing purity, impurities, aggregates and bacterial endotoxin? FDA reviewed one public certificate that tested appearance, identity and purity, and left assay, impurities, endotoxin and aggregates untested.
Sixth, what is being treated, and is there an approved therapy for that problem? FDA noted that approved treatments with established efficacy exist for wound management, and that question costs nothing to ask.
Compare providers on those six answers rather than on price, starting at the clinic finder. If BPC-157 comes up in the same conversation, our FDA vote explainer and the BPC-157 compound page cover that molecule separately, with the same rule applied: trace each claim to a source.
Frequently asked questions
Is there a standard TB-500 dosage?
No. FDA found no article in which TB-500 was given to humans and no human study of its pharmacokinetics by any route, so no human dose exists to standardize. A figure presented as standard came from an animal study, a product listing or a forum.
Where do the 2 mg to 2.5 mg TB-500 dosing charts come from?
From product listings and forum repetition, not from a clinical trial. FDA documented vials sold in 2 mg, 3 mg, 5 mg, 10 mg and 15 mg sizes marked for research use only. Those are package sizes, and none carries a route, a frequency or a published outcome in people.
Did the horse study give a usable human dose?
No. Ho and colleagues gave geldings a single 10 mg subcutaneous dose to build a doping test, and plasma levels peaked at 0.05 to 0.08 ng/mL before becoming unquantifiable 6 to 10 hours later. That describes how the peptide moves through a horse.
Is TB-500 the same as thymosin beta-4?
No, and FDA says so directly: “thymosin beta-4 and TB-500 are not the same substance.” TB-500 is a seven amino acid fragment with an acetyl group added; thymosin beta-4 is the full 43 amino acid protein, and the human trials cited for TB-500 used that larger protein.
Is TB-500 FDA approved?
No. FDA states that neither TB-500 (free base) nor TB-500 acetate is a component of an FDA-approved drug, that neither has a USP or NF monograph, and that it proposed not adding either to the 503A bulk substances list. The current text of 21 CFR 216.23 does not include it.
Can a US pharmacy compound TB-500?
Not lawfully as a 503A bulk substance on the current list. FDA found no outsourcing facility reporting TB-500 compounding and no pharmacy marketing a compounded TB-500 product. Anyone weighing a specific product should ask a licensed clinician or pharmacist about that product by name.
Sources:
- FDA briefing document, TB-500-related bulk drug substances, Pharmacy Compounding Advisory Committee, dated May 15, 2026 (retrieved October 28, 2026).
- FDA, Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks, TB-500 entry, retrieved October 28, 2026.
- eCFR, 21 CFR 216.23, bulk drug substances that can be used to compound under section 503A, current text from 84 FR 4710, February 19, 2019 (retrieved October 28, 2026).
- Ho et al., Doping control analysis of TB-500 in equine urine and plasma by liquid chromatography-mass spectrometry, J Chromatogr A 1265:57-69, 2012.
- Rahaman et al., Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats, J Chromatogr B 1235:124033, 2024.
This page is educational information, not medical advice, a diagnosis, or a treatment recommendation. It does not recommend any peptide, medication, pharmacy, clinic, or treatment plan, and it makes no claim that any unapproved substance is safe or effective. Compounded drugs are not FDA-approved, and FDA does not verify their safety, effectiveness, or quality before they are marketed. Doses vary, and the decision about a prescription belongs to a licensed clinician who knows your history. Talk to your prescriber about your own situation, and see our full medical disclaimer.