Is TB-500 the same as thymosin beta-4?

No. Thymosin beta-4 is a 43-amino-acid peptide. TB-500 is a 7-amino-acid fragment of it, residues 17 through 23, with an acetyl group added. FDA's May 2026 review states directly that the two are not the same substance, and that the acetyl group can change how the molecule behaves. The human trials usually cited for TB-500 used full-length thymosin beta-4, mostly as 0.1% eye drops.

How many units is 2 mg of TB-500?

It depends on the concentration. At 5,000 mcg per mL (a 10 mg vial with 2 mL of bacteriostatic water, or a 5 mg vial with 1 mL), 2 mg is 0.40 mL, or 40 units on a U-100 insulin syringe. At 2,500 mcg per mL (a 5 mg vial with 2 mL), it is 0.80 mL, or 80 units. At 2,000 mcg per mL (a 2 mg vial with 1 mL), 2 mg is the whole syringe and the whole vial. This is math, not a dosing recommendation.

Is there a human dose for TB-500?

No. For its May 2026 review, FDA searched the published literature, ClinicalTrials.gov and its own adverse-event systems and found no clinical study or human exposure data for TB-500 by any route. The closest thing to a human figure is the 3 mg/mL injectable concentration a compounding pharmacy proposed to FDA, which is a product strength rather than a dose.

How does TB-500 work?

The proposed mechanism is actin binding. The LKKTETQ sequence is the actin-binding region of thymosin beta-4, and binding free G-actin is thought to support cell migration, new blood vessel growth and tissue repair. FDA's review notes it remains undetermined whether actin binding actually accounts for the effects attributed to the fragment.

Does TB-500 actually heal tendons?

Unsettled, and weaker than the marketing suggests. A 2026 rat study of transected Achilles tendons found TB-500 at 60 mcg/kg/day improved load to failure and tendon architecture. But FDA identified no in-vivo wound-healing study for TB-500, and in one laboratory study it did nothing to fibroblast wound closure at 50 mcg/mL while one of its metabolites did. Full-length thymosin beta-4 has the stronger healing literature, and it is a different molecule.

Can TB-500 be stacked with BPC-157?

It is commonly sold as a blend, and the one study that tested the combination found no added benefit. In a 2026 rat Achilles tendon model, BPC-157 at 10 mcg/kg/day and TB-500 at 60 mcg/kg/day each improved tendon architecture, and the combination did no better than either alone. No human data exists for either compound or for the combination.

Is TB-500 legal to buy?

It is sold as a research chemical, not for human use, and it is not FDA-approved. FDA's advisory committee recommended it for the Section 503A compounding list on July 23, 2026, against FDA staff's own recommendation, but that vote changes nothing until FDA completes rulemaking. It is prohibited in tested sport at all times.

TB-500 Dosage Chart (2mg/5mg) and What It Actually Is

Last reviewed: September 18, 2026

TB-500 has no established human dose. FDA's May 2026 review found no clinical study of TB-500 in humans by any route, so every number on this page is vial math or a range reported in research and community protocols, labeled as such. The ranges in circulation are 2 to 2.5 mg subcutaneously two to three times weekly for an initial period, then a lower maintenance amount, and a separate lower concentration of 500 mcg to 1 mg. At 5,000 mcg per mL (a 10 mg vial with 2 mL of bacteriostatic water, or a 5 mg vial with 1 mL), 2 mg is 0.40 mL, which is 40 units on a U-100 insulin syringe.

TB-500 is also not thymosin beta-4, though the names are used interchangeably across the market. The human trials usually cited for TB-500 studied the full-length molecule. Read the molecule identity section below before comparing any dose. Where TB-500 stands with regulators is laid out in the FDA's 2026 peptide reclassification.

This is research information, not medical advice. TB-500 is not FDA-approved.

TB-500 Dosage Chart: 2 mg, 5 mg, and 10 mg Vials

TB-500 vial math at 5,000 mcg/mL (10 mg vial + 2 mL, or 5 mg vial + 1 mL)
Amount	Volume	U-100 units	Draws per 10 mg vial	Draws per 5 mg vial
500 mcg	0.10 mL	10 units	20	10
1 mg	0.20 mL	20 units	10	5
1.25 mg	0.25 mL	25 units	8	4
2 mg	0.40 mL	40 units	5	2
2.5 mg	0.50 mL	50 units	4	2

TB-500 vial math at 2,500 mcg/mL (5 mg vial + 2 mL)
Amount	Volume	U-100 units	Draws per vial
500 mcg	0.20 mL	20 units	10
1 mg	0.40 mL	40 units	5
1.25 mg	0.50 mL	50 units	4
2 mg	0.80 mL	80 units	2
2.5 mg	1.00 mL	100 units (a full syringe)	2

TB-500 vial math at 2,000 mcg/mL (2 mg vial + 1 mL)
Amount	Volume	U-100 units	Draws per vial
500 mcg	0.25 mL	25 units	4
1 mg	0.50 mL	50 units	2
1.25 mg	0.625 mL	62.5 units	1
2 mg	1.00 mL	100 units (the whole vial)	1
2.5 mg	1.25 mL	Does not fit a U-100 syringe	Not possible from one 2 mg vial

These are math references, not a dosing schedule. Confirm the vial label, the volume of bacteriostatic water you actually added, and your syringe type before trusting any number. For a vial size or volume the tables do not cover, the calculator will convert a TB-500 amount into syringe units from whatever concentration you mixed. When TB-500 and BPC-157 come in one research vial, a separate tool will split a blended draw into each compound's delivered amount.

Two amounts to watch. A 2 mg vial reconstituted with 1 mL holds exactly one 2 mg draw and nothing more. At that concentration, 2.5 mg is 1.25 mL, which won't fit in a U-100 insulin syringe. If your protocol calls for 2 to 2.5 mg, use a larger vial or less water and recheck the math. TB-500 free base is reported to be soluble at 50 mg per mL, so concentration is not limited by solubility.

TB-500 Is Not Thymosin Beta-4

Thymosin beta-4 is a 43-amino-acid peptide found in blood, plasma, saliva, tears, and wound fluid. TB-500 is a 7-amino-acid fragment of it, residues 17 through 23, with an acetyl group on the leading leucine. FDA's May 2026 review states this directly: it notes that several websites call TB-500 a synthetic version of thymosin beta-4 and use the terms interchangeably, and that they are not the same substance.

The difference is not cosmetic. FDA reviewers explain that acetylation permanently changes a peptide's charge, hydrophobicity, and size, which can change its lifespan, folding, and binding, so the unacetylated fragment's pharmacology does not carry over to the acetylated one.

Then someone tested it. A 2024 study compared TB-500 and its breakdown products in scratch-wounded fibroblast cultures. Only one compound produced significant wound closure, and it was not TB-500. It was Ac-LKKTE, a metabolite. The authors concluded that the wound-healing activity previously reported for TB-500 may be due to that metabolite rather than the parent form (Rahaman et al., 2024). FDA reached the same conclusion from the other direction, noting that nonclinical pharmacological evidence is currently lacking to support TB-500's potential to promote wound healing.

Three molecules sold under two names
Molecule	What it is	Human data
Thymosin beta-4, full length	43 amino acids, occurs naturally in blood, plasma, saliva, tears and wound fluid	Yes. A completed Phase 1a gave single intravenous doses of 0.05 to 25 mcg/kg to 54 healthy volunteers. A Phase 3 of a 0.1% ophthalmic solution for neurotrophic keratopathy is ongoing.
LKKTETQ, unacetylated	The 7-amino-acid actin-binding fragment, residues 17 to 23	None. Promoted dermal wound repair applied topically in aged and diabetic mice, comparably to the full-length molecule (Philp et al., 2003).
TB-500, acetylated LKKTETQ	What is sold and injected as TB-500. The acetyl group sits on the leading leucine	None by any route, per FDA's May 2026 review. No in-vivo wound-healing study identified.

For scale, the highest single dose in the full-length thymosin beta-4 escalation program was 25 micrograms per kilogram intravenously, about 1.75 mg for a 70 kg adult. Figures quoted in the tens or hundreds of milligrams per day do not come from that program.

TB-500 Research: Three Tiers of Evidence

Preclinical evidence exists for the parent molecule, thymosin beta-4, in tissue repair. In a rat full-thickness wound model, thymosin beta-4 applied topically or intraperitoneally increased re-epithelialization by 42 percent at four days and by as much as 61 percent at seven days versus saline controls, alongside greater collagen deposition and angiogenesis (Malinda et al., PubMed 10469335). In a rat incisional wound study, locally applied thymosin beta-4 healed with minimal scarring and no loss in wound-breaking strength, producing more organized, mature collagen than controls (PubMed 20536458). In a rat medial collateral ligament model, thymosin beta-4 delivered in a fibrin sealant produced uniform, evenly spaced collagen fiber bundles and significantly increased collagen fibril diameter at four weeks.

Human evidence is for the full-length molecule, not the fragment. Clinical trials of recombinant thymosin beta-4 have studied intravenous dosing for conditions such as acute myocardial infarction and in healthy-volunteer safety studies. Those doses are intravenous and expressed in micrograms per kilogram or clinical milligram boluses, not the subcutaneous flat milligram amounts used with research-market TB-500.

Direct human evidence for the fragment is absent, and it is now absent on the record. For its May 2026 review, FDA searched the published literature, ClinicalTrials.gov, and its own adverse-event systems and found no clinical study or human exposure data for TB-500 by any route, no animal toxicity studies, and no reports in its adverse-event system. So the figures circulated in research-peptide protocols, commonly 2 to 2.5 mg subcutaneously two to three times weekly for an initial period followed by a lower maintenance amount, are community and clinician-reported. No published source reports the loading duration, the maintenance amount, or the rationale for either.

TB-500 and thymosin beta-4 doses by source
Source	Dose and route	Evidence label
Community protocols	2 to 2.5 mg subcutaneous, 2 to 3 times weekly for an initial period, then a lower maintenance amount. A separate convention uses 500 mcg to 1 mg.	Community-reported convention. No human study supports either range, and no published source gives the loading or maintenance durations.
Compounding nomination to FDA	3 mg/mL, subcutaneous or intramuscular	Proposed product concentration, not a dose and not an approved product.
Horse pharmacokinetics	10 mg subcutaneous, single dose	Animal PK only. Plasma peaked at 0.05 to 0.08 ng/mL by 1 to 2 hours and was unmeasurable by 6 to 10 hours (Ho et al., 2012).
Rat Achilles tendon model	60 mcg/kg/day intraperitoneally, 4 weeks	Animal only. Improved load to failure and tendon architecture; combining with BPC-157 added nothing (Bicer et al., 2026).
Thymosin beta-4, human trials	0.1% ophthalmic solution; 0.05 to 25 mcg/kg intravenous	Human data, but a different molecule. Do not carry across.
TB-500, human	None	Not established. FDA identified no clinical study or human exposure data by any route.

TB-500 Pharmacokinetics: Short Exposure, Long-Lived Fragments

The only in-vivo pharmacokinetic study is in horses. After a single 10 mg subcutaneous dose, plasma levels peaked at 0.05 to 0.08 ng/mL between one and two hours and were no longer measurable between six and ten hours (Ho et al., 2012). No intravenous comparison exists, so subcutaneous bioavailability has never been established, and no human pharmacokinetic data are available.

Metabolism runs from the tail end, stripping amino acids one at a time to give acetylated LKKTET, LKKTE, LKKT, LKK and LK. The same pattern appears in horse plasma and urine, in rat urine, and in human serum, kidney microsomes, liver microsomes, and liver S9 fraction (Ho et al., 2012; Zvereva et al., 2016; Rahaman et al., 2024). In rats, Ac-LK was the most abundant fragment over the first six hours, and Ac-LKK was still detectable at 72 hours. The fragments outlast the parent by a wide margin, and one of them, Ac-LKKTE, is the compound that produced wound closure in vitro when TB-500 itself did not.

How TB-500 Differs from Other Healing Peptides

TB-500 often gets compared to BPC-157. Both are studied for recovery, but BPC-157's literature centers on gut healing and partly on growth hormone pathways, while TB-500's centers on actin regulation across a broader range of tissues. The two are also studied together with GHK-Cu as a three-peptide repair stack, covered in our guide to the GLOW blend that adds GHK-Cu. Unlike growth hormone secretagogues such as Ipamorelin or CJC-1295, TB-500 does not stimulate growth hormone production, which is why it comes up for people who cannot or do not want to influence their GH levels.

TB-500 in Athletic and Recovery Contexts

TB-500 is prohibited in sport at all times. The World Anti-Doping Agency lists it, and Global DRO carries it as prohibited, so a positive finding is a sanction regardless of when or why it was used. Detection is not theoretical: a racing laboratory confirmed TB-500 and its metabolites in horse plasma at 0.02 ng/mL and urine at 0.01 ng/mL after a single dose (Ho et al., 2012), and because the fragments outlast the parent molecule, the detection window is wider than the short plasma half-life suggests.

For how TB-500 sits beside other compounds used in training, see the guide to peptides for athletic performance. For the rehabilitation side, the guide to peptides for injury recovery covers where a compound like this fits against a rehab protocol.

TB-500 Storage and Handling

TB-500 arrives as lyophilized powder that requires reconstitution with bacteriostatic water. Vials are typically 2 mg, 5 mg or 10 mg. Reported stability figures differ by form and by source, and vendor labels often do not say which form is in the vial. For the free base: sealed powder under nitrogen, away from moisture and light, 2 years at -80 degrees C or 1 year at -20 degrees C, and 6 months at -80 or 1 month at -20 once in solution. For the acetate, the supplier certificate in FDA's review said 2 to 8 degrees C, while public sources said below -15 degrees C; FDA noted the discrepancy but did not resolve it. Treat refrigerator storage as short-term only, and treat heat, light, and repeated temperature swings as the things that degrade the material.

TB-500 Safety Considerations

FDA's May 2026 review found no clinical safety data for TB-500 by any route, no acute, repeat-dose, genotoxicity, reproductive or carcinogenicity studies in animals, and no reports in its adverse-event system. Absence of reports is not evidence of safety. It reflects that almost nobody files them. FDA also flagged immunogenicity, the body forming antibodies to an injected peptide, as a specific concern for injectable routes.

Theoretical concerns follow from the mechanism. Because the peptide is studied for promoting cell movement and new blood vessel growth, questions arise about cells that should not be encouraged to migrate or vascularize. No evidence suggests TB-500 causes cancer, and no study has examined it, which is the point: anyone with a malignancy history is weighing an unstudied question, not a reassuring one. Long-term human safety data does not exist.

TB-500 Regulatory Status in 2026

TB-500 is not FDA-approved for any use, and no thymosin beta-4 fragment product is approved in the United States, Canada, Australia, the United Kingdom or the European Union.

On July 23, 2026, FDA's Pharmacy Compounding Advisory Committee reviewed TB-500 free base and acetate for the Section 503A Bulks List, the list of bulk substances a licensed compounding pharmacy may use to fill a prescription. FDA staff recommended against adding either form, citing poor physicochemical characterization, no evidence of effectiveness, no human safety data, and immunogenicity risk from injectable routes. The committee disagreed, voting 8 to 6 with 1 abstention to recommend adding it. The vote is advisory: it does not add TB-500 to the list, approve any product, or authorize compounding, and FDA must complete notice-and-comment rulemaking first. We will update this section when the FDA acts.

TB-500 Quality and Sourcing Considerations

Without independent testing, a buyer cannot verify what is in the vial. Certificates of analysis typically use HPLC for purity and mass spectrometry for identity, and a certificate confirming those two things says nothing about endotoxin, sterility, or heavy metals. What separates suppliers is what their certificates cover, which is how each supplier we track is scored.

TB-500 is one of the harder peptides to buy with confidence because the market sells both the 7-amino-acid fragment and full-length thymosin beta-4 under overlapping names, and a truncated sequence can still read as pure on basic HPLC while being a different molecule. Mass spectrometry data, not HPLC alone, is what verifies the sequence.

Limitless Biotech publishes per-batch HPLC and mass spectrometry results from a named laboratory, and what those Limitless certificates cover, including sterility and endotoxin testing from a second lab, is in the review.

Biolongevity Labs also publishes both HPLC and mass spectrometry data per batch and manufactures in the US; how Biolongevity documents each batch is covered separately.

Very cheap TB-500 should raise questions, and a high price guarantees nothing without independent verification. The certificate is the evidence, not the price.

Where to Find Current TB-500 Codes

TB-500 is available from Biolongevity Labs on its own at 10mg and inside several of its blends. Anyone already buying there can apply PROBIO15, Project Biohacking's code, for 15 percent off. How to enter the Biolongevity Labs discount code is shown on its coupon page, which changes whenever the code does.

Other suppliers carry TB-500 too, each with a Project Biohacking code of its own. You can compare them on one page listing the codes we currently hold.

For Ameano Peptides, the Project Biohacking code PROBIO takes 10 percent off at checkout. Its shop names the fragment TB-500 Frag 17-23 10mg, and that Project Biohacking code, PROBIO, is the Ameano Peptides coupon code for the store as a whole.

Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a 43-amino-acid peptide. TB-500 is a 7-amino-acid fragment of it, residues 17 through 23, with an acetyl group added. FDA's May 2026 review states directly that the two are not the same substance, and that the acetyl group can change how the molecule behaves. The human trials usually cited for TB-500 used full-length thymosin beta-4, mostly as 0.1% eye drops.
How many units is 2 mg of TB-500?
It depends on the concentration. At 5,000 mcg per mL (a 10 mg vial with 2 mL of bacteriostatic water, or a 5 mg vial with 1 mL), 2 mg is 0.40 mL, or 40 units on a U-100 insulin syringe. At 2,500 mcg per mL (a 5 mg vial with 2 mL), it is 0.80 mL, or 80 units. At 2,000 mcg per mL (a 2 mg vial with 1 mL), 2 mg is the whole syringe and the whole vial. This is math, not a dosing recommendation.
Is there a human dose for TB-500?
No. For its May 2026 review, FDA searched the published literature, ClinicalTrials.gov and its own adverse-event systems and found no clinical study or human exposure data for TB-500 by any route. The closest thing to a human figure is the 3 mg/mL injectable concentration a compounding pharmacy proposed to FDA, which is a product strength rather than a dose.
How does TB-500 work?
The proposed mechanism is actin binding. The LKKTETQ sequence is the actin-binding region of thymosin beta-4, and binding free G-actin is thought to support cell migration, new blood vessel growth and tissue repair. FDA's review notes it remains undetermined whether actin binding actually accounts for the effects attributed to the fragment.
Does TB-500 actually heal tendons?
Unsettled, and weaker than the marketing suggests. A 2026 rat study of transected Achilles tendons found TB-500 at 60 mcg/kg/day improved load to failure and tendon architecture. But FDA identified no in-vivo wound-healing study for TB-500, and in one laboratory study it did nothing to fibroblast wound closure at 50 mcg/mL while one of its metabolites did. Full-length thymosin beta-4 has the stronger healing literature, and it is a different molecule.
Can TB-500 be stacked with BPC-157?
It is commonly sold as a blend, and the one study that tested the combination found no added benefit. In a 2026 rat Achilles tendon model, BPC-157 at 10 mcg/kg/day and TB-500 at 60 mcg/kg/day each improved tendon architecture, and the combination did no better than either alone. No human data exists for either compound or for the combination.
How should TB-500 be stored?
Reported figures differ by form and source. For the free base: sealed powder under nitrogen, away from moisture and light, 2 years at -80 degrees C or 1 year at -20 degrees C, and 6 months at -80 or 1 month at -20 once in solution. For the acetate, the supplier certificate in FDA's review said 2 to 8 degrees C while public sources said below -15 degrees C. Treat refrigerator storage as short-term only.
Is TB-500 legal to buy?
It is sold as a research chemical, not for human use, and it is not FDA-approved. FDA's advisory committee recommended it for the Section 503A compounding list on July 23, 2026, against FDA staff's own recommendation, but that vote changes nothing until FDA completes rulemaking. It is prohibited in tested sport at all times.

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Important Disclaimer: The content on Project Biohacking is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any changes to your health regimen, starting new supplements, peptides, or protocols. Nothing on this site establishes a doctor–patient relationship, and you use the information at your own risk. Research compounds discussed here are sold for laboratory research purposes only and are not approved for human or veterinary use or consumption.

TB-500 Dosage Chart, Molecule Identity, and 2026 FDA Status

From tissue repair to injury recovery, TB-500 has captured the attention of athletes and biohackers alike. Discover how this healing peptide actually works.