Underground Biohacking
Recovery

TB-500

Chris Hallewell, founder of Underground Biohacking

By , Founder, Underground Biohacking

Last reviewed

Research use only. Not FDA-approved. Banned by WADA.

TB-500 is a lab made copy of a seven amino acid piece of thymosin beta-4, a natural repair protein. No clinical trial has ever tested TB-500 in people. The healing evidence comes from rats, mice, horses and cell cultures. Human trials do exist, but they used the full thymosin beta-4 protein. That is a bigger, different molecule. The FDA lists TB-500 as a bulk substance it has no human exposure data for.

What is TB-500?

TB-500 is a peptide of seven amino acids: leucine, lysine, lysine, threonine, glutamic acid, threonine and glutamine. Chemists write that as LKKTETQ. It is a copy of positions 17 to 23 of thymosin beta-4, a 43 amino acid protein your body already makes. The copy carries an acetyl group on one end, which slows enzymes down. That short stretch is the actin binding site. Actin builds the internal scaffold that lets a cell hold its shape and crawl. Thymosin beta-4 grips actin and controls how it assembles. Researchers narrowed the protein's repair activity down to this one region, then made that region on its own. That is where TB-500 came from. So TB-500 is a fragment, not the protein. This matters when you read the research. Thymosin beta-4 has been through several small human trials. TB-500 has been through none. It first appeared as a veterinary preparation, and doping control labs now screen for it. Sellers often blur the two names. The evidence does not transfer between them.

What is TB-500 used for?

  • In people with severe dry eye, phase 2 drops of thymosin beta-4 itself, not TB-500, cut discomfort and corneal staining.[1]Human study
  • In people with pressure and stasis ulcers, thymosin beta-4 itself, not TB-500, sped up healing in two phase 2 trials.[2]Human study
  • In a second phase 2 dry eye trial, drops of the full protein, again not TB-500, improved signs and symptoms with no adverse events.[3]Human study
  • In ten people after a heart attack, stem cells pre treated with thymosin beta-4, not TB-500, improved heart function more than untreated cells.[4]Human study
  • In rats with a cut Achilles tendon, TB-500 itself produced tendons that took more load before failing.[5]Animal or lab study only
  • In aged mice, the LKKTETQ fragment that TB-500 is made of healed skin wounds as well as the whole protein did.[6]Animal or lab study only
  • In an animal alkali burn model, a gel carrying the TB-500 sequence sped up surface healing of the eye and cut inflammation.[7]Animal or lab study only
TB-500 dosage chart
Typical dose2-2.5mg twice weekly during loading, 2-2.5mg once weekly maintenance
Cycle length4-6 week loading phase, then 2-4 week maintenance
FormInjectable (subcutaneous or intramuscular)

How many units is your TB-500 dose?

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How does TB-500 work?

Thymosin Beta-4 fragment that promotes cell migration, angiogenesis, and reduces inflammation systemically. Unlike BPC-157 which works locally, TB-500 travels through the bloodstream to reach injured tissue throughout the body.

How much TB-500 should you take?

2-2.5mg twice weekly during loading, 2-2.5mg once weekly maintenance

How long should you run TB-500?

4-6 week loading phase, then 2-4 week maintenance

How is TB-500 supplied?

Injectable (subcutaneous or intramuscular)

What are the side effects of TB-500?

EffectHow seriousWhat to watch
No human trial has ever tested TB-500. There is no human safety record for this peptide at all.UnknownNothing is validated. Tell a doctor if you are using it.
In the first in human study of the parent protein given by drip, side effects were mild to moderate. That trial tested thymosin beta-4, not TB-500.[8]Mild to moderate in that trialInjection site reactions and any allergic response
Nobody has established when it should be used, or for how long. Reviewers in sports medicine say this is still unknown.[9]UnknownNone validated. Treat any use as experimental.
The parent protein sits at high levels in many cancers. Nobody has tested whether the fragment affects tumour growth in people.[10]Unknown, theoreticalAny personal or family cancer history is worth raising with a doctor

Is TB-500 legal in 2026?

Checked on 6 August 2026. The FDA names TB-500 on its page for bulk drug substances that may present significant safety risks. The entry reads "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500". It sits in category 2. FDA says compounded drugs containing it may pose a risk for immunogenicity. That means your immune system may react to it. FDA also flags peptide related impurities. FDA states it has not identified any human exposure data for products containing this fragment. That page was current as of 22 April 2026. TB-500 is not an approved medicine. An advisory committee vote is advice, not law, and changes none of this.

Status checked against the primary source.

Where to buy TB-500

Running TB-500 in your next protocol cycle?

Check out our recommended sources list to find vetted vendors you can trust.

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Where to source it

The hard part with TB-500 isn't the protocol. It's finding a supplier that can prove what's in the vial. We assessed dozens against per-batch, third-party testing. A handful passed.

See the sources that passed →

TB-500 protocols

Deep dives on TB-500

Frequently Asked Questions

Is TB-500 the same thing as thymosin beta-4?
No. Thymosin beta-4 is a natural protein with 43 amino acids. TB-500 is a lab made copy of just seven of them, positions 17 to 23. That short piece carries a lot of the protein's repair activity in animal work. But it is a different molecule, with different size and behaviour. When you see a human trial of thymosin beta-4, it did not test TB-500. Sellers often treat the two names as interchangeable. They are not.
Has TB-500 ever been tested in a human trial?
No. A search of the published medical literature turns up no clinical trial of TB-500 in people. What exists is animal and laboratory work: rats with cut tendons, mice with skin wounds, cell cultures, and horses used in doping research. The FDA says the same thing in plainer words. It has not identified any human exposure data for products containing this fragment. So every claim about what it does in a person is an extrapolation.
Does the human dry eye research count as evidence for TB-500?
Not directly. Those trials used thymosin beta-4 eye drops, the full protein, on the surface of the eye. One phase 2 trial in severe dry eye showed clear improvement. Another missed both of its main endpoints, though it improved several secondary ones. Neither tested TB-500, and neither tested an injection. Carrying an eye drop result across to an injected fragment of a different size is not something the data supports.
Is TB-500 banned in sport?
Yes. A 2026 review in a sports medicine journal states that thymosin beta-4 and TB-500 both remain banned substances in sport. Anti doping labs have built tests aimed straight at it. Published methods detect the acetylated LKKTETQ peptide and its breakdown products in urine and plasma at very low levels. It has also been detected in horses after it was given to them. If you compete under an anti doping code, using it risks a sanction.
Can a pharmacy legally compound TB-500?
No. FDA has placed thymosin beta-4 fragment, named on that page as TB-500, in category 2 of the bulk drug substances lists. Category 2 covers substances FDA identified as potentially presenting significant safety risks. The stated concerns are immunogenicity and peptide related impurities, plus the absence of any human exposure data. TB-500 is not an approved drug in the United States. An advisory committee vote is advice, not law, and changes nothing.
What should I ask a doctor before considering it?
Ask what human evidence exists for this exact molecule, and expect the honest answer to be none. Ask what is actually in the vial, since no approved manufacturer makes it. Ask about immune reactions, because that is the risk FDA names first. Ask about your own cancer history. The parent protein sits at high levels in many tumours, and nobody has tested the fragment in people.

References

  1. 1.Sosne G, et al. (2015). Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. PMID: 25826322. DOI: 10.1097/ICO.0000000000000379.
  2. 2.Treadwell T, et al. (2012). The regenerative peptide thymosin β4 accelerates the rate of dermal healing in preclinical animal models and in patients. Annals of the New York Academy of Sciences. PMID: 23050815. DOI: 10.1111/j.1749-6632.2012.06717.x.
  3. 3.Sosne G, Ousler GW (2015). Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial conducted using the controlled adverse environment (CAE™) model. Clinical ophthalmology (Auckland, N.Z.). PMID: 26056426. DOI: 10.2147/OPTH.S80954.
  4. 4.Zhu J, et al. (2016). Safety and efficacy of autologous thymosin β4 pre-treated endothelial progenitor cell transplantation in patients with acute ST segment elevation myocardial infarction: A pilot study. Cytotherapy. PMID: 27288307. DOI: 10.1016/j.jcyt.2016.05.006.
  5. 5.Biçer O, et al. (2026). Effects of BPC-157 and TB-500 on Achilles tendon healing in rats: A histopathological and biomechanical study. Joint diseases and related surgery. PMID: 42542926. DOI: 10.52312/jdrs.2026.2951.
  6. 6.Philp D, et al. (2003). Thymosin beta 4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. Wound repair and regeneration. PMID: 12581423. DOI: 10.1046/j.1524-475x.2003.11105.x.
  7. 7.Lu P, et al. (2025). Alkaline Phosphatase-Triggered Spatiotemporal Repair of Corneal Injury with TB500 Peptide Hydrogel. ACS applied materials & interfaces. PMID: 41359360. DOI: 10.1021/acsami.5c14652.
  8. 8.Wang X, et al. (2021). A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers. Journal of cellular and molecular medicine. PMID: 34346165. DOI: 10.1111/jcmm.16693.
  9. 9.Mayfield CK, et al. (2026). Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians. The American journal of sports medicine. PMID: 41476424. DOI: 10.1177/03635465251357593.
  10. 10.Chao TC, et al. (2014). In vivo growth suppression of CT-26 mouse colorectal cancer cells by adenovirus-expressed small hairpin RNA specifically targeting thymosin beta-4 mRNA. Cancer gene therapy. PMID: 25124811. DOI: 10.1038/cgt.2014.43.

This content is for educational purposes only. These compounds are intended for research use. Nothing here is medical advice.