TB-500: research, side effects and dosage in studies

In short

TB-500 is a synthetic peptide that the FDA describes as a seven-amino-acid piece of thymosin beta-4 [2]regulator. It has no marketing authorisation as a medicine [14]regulator.

• All the evidence comes from animal and laboratory experiments: the FDA has found no human exposure data for TB-500 [2]regulator.
• In rats, TB-500 strengthened a repaired Achilles tendon in a four-week experiment [3]C. The result applies to rats.
• Thymosin beta-4 is a different substance from TB-500, so its human studies are not studies of TB-500 [5]D [9]A.
• The content of TB-500 products bought online did not consistently match their descriptions [11]D.
• In Finland TB-500 is in Annex 1 A of the medicines list, so it is treated like a prescription-only medicine [12]regulator. In sport it is prohibited at all times (WADA S2.3) [13]regulator.

What is TB-500?

TB-500 is a synthetic peptide. The FDA describes it as a fragment of thymosin beta-4 with the amino acid sequence LKKTETQ [2]regulator. Laboratory analyses have identified the main ingredient of TB-500 preparations as the N-terminally acetylated form of this sequence, Ac-LKKTETQ, which corresponds to amino acids 17 to 23 of thymosin beta-4 [5, 6]D.

Thymosin beta-4 is a much longer protein that the human body makes itself. TB-500 is only a short piece of it [5]D.

TB-500 has been described as a veterinary preparation whose misuse has been policed in horse racing [6]D. Fimea gives TB-500 as an example name under which peptide products are sold online, and according to Fimea the label "for research use only" means the product is not intended for humans [1]regulator. Basics: What are peptides?. All substances: Peptides A-Z.

Evidence at a glance

Each cell gives the kind of study and its source. The letter is the evidence level, not the result.

"-" = no such study is known.

What is TB-500 studied for?

None of the uses below is approved, and none has been studied in humans [2]regulator.

• Tendon injuries: one rat study of a cut and repaired Achilles tendon [3]C, see Promising, but only in animal and cell studies.
• Skin wounds: a mouse study that used the LKKTETQ amino acid sequence, not commercial TB-500 [8]C, and a cell study of TB-500 breakdown products [7]D.
• Doping control: some studies examine what TB-500 products contain and how the substance is detected in samples [5, 6, 11]D.

Claims online. The claim that it speeds up healing in humans rests on animal experiments [3, 8]C. A review says many unapproved peptides show favourable results in animal models, but rigorous human safety data are scarce [4].

How does TB-500 work?

Nobody knows how TB-500 works. A 2024 study states that the biological effects of TB-500 had not been documented, and that effects described earlier were seen with the non-acetylated LKKTETQ sequence [7]D.

In the same study, in skin fibroblasts only the TB-500 breakdown product Ac-LKKTE sped up wound closure compared with control, not TB-500 itself [7]D. So it is not known whether TB-500 itself acts, or its breakdown products.

Has TB-500 been studied in humans?

No, the FDA has found no human exposure data for products containing TB-500 [2]regulator.

Human studies

• Knee injections (2021). In a retrospective chart review from one clinic, four patients had received knee injections of BPC-157 and thymosin beta-4 without a comparison group. The article does not say whether the substance was TB-500 [10]B.
• Thymosin beta-4 (2021). Full-length thymosin beta-4 has been given to healthy volunteers in a phase 1 trial, but it is a different substance from TB-500 [9]A.

Promising, but only in animal and cell studies

These findings look good, but they have not been tested in humans [2]regulator. Results from animal and cell studies cannot be transferred to humans, nor do they show the effects of a product sold online, because the content of such products can differ from its description [11]D.

• Tendon injuries no human studies

  In a rat study, the cut and repaired Achilles tendons of 32 rats were treated for four weeks with BPC-157, TB-500, their combination or nothing (8 rats per group). In the TB-500 group the tendon withstood a higher load before failing than in controls, and scores describing tissue structure were better [3]C.

  If it held in humans: people might recover faster from a tendon injury or tendon surgery.

  Why it might not translate: the groups were small, the experiment lasted four weeks, and the authors describe the findings as preliminary [3]C. The substance was given into the abdominal cavity [3]C.

  Evidence now: one rat study [3]. No human study [2]regulator.

• Skin wounds no human studies

  In a mouse study, a seven-amino-acid synthetic LKKTETQ peptide promoted skin wound healing in aged mice comparably to full-length thymosin beta-4 [8]C. In skin fibroblasts only the breakdown product Ac-LKKTE sped up wound closure, not TB-500 itself [7]D.

  If it held in humans: slow-healing wounds might be treated with it.

  Why it might not translate: the mouse study used the non-acetylated amino acid sequence, not a commercial TB-500 preparation [8]C, and in the cell test TB-500 itself did not speed up wound closure [7]D.

  Evidence now: one mouse study and one cell study [7, 8]. No human study [2]regulator.

Who studies TB-500?

Much of the research on TB-500 consists of laboratory analyses of what TB-500 products contain and how the substance is identified in doping samples [5, 6, 11]D. There are few experiments on effects: one rat tendon study [3]C, one mouse wound study with the amino acid sequence [8]C and one cell study of TB-500 breakdown products [7]D.

Who wrote this page: the editorial team

This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.

How long does TB-500 stay in the body?

How long TB-500 stays in the human body has not been studied [2]regulator. In a laboratory and rat study, TB-500 was broken down into shorter pieces. In rats the main breakdown product was Ac-LK, and the breakdown product Ac-LKK was detectable in urine for up to 72 hours [7]C.

What are the side effects of TB-500?

There are no data on the harms of TB-500 in humans. The FDA has found no human exposure data and lacks important information on whether the substance would cause harm if given to humans [2]regulator.

What users report. In the Reddit accounts we compiled (not research), 329 of 879 people (37%) reported some harm, most often: injection site reaction (82, 9%), mood or anxiety (51, 6%) and fatigue or lethargy (39, 4%). People tend to post when something goes wrong, so this share does not tell how common harms are. Almost everyone used TB-500 together with BPC-157: 865 of 879 people (98%) used other substances at the same time, and 856 (97% of all) used BPC-157 specifically. So the figures describe TB-500 used with BPC-157, not TB-500 on its own. The harms in detail: TB-500 user experiences.

Risks in the products

The FDA says products containing TB-500 may carry a risk of immune reactions by certain routes of administration, because the peptide can aggregate and products may contain peptide-related impurities [2]regulator.

According to Fimea, there is no reliable information on the content, quality and safety of products sold as peptides. For injectable products, impurities such as endotoxins that end up in the product during manufacture raise the risk of serious health hazards [1]regulator.

What has not been studied

• Whether TB-500 is safe for humans: the FDA lacks information on whether the substance would cause harm in humans [2]regulator.
• What the substance does over the long term: the rat study lasted four weeks, and the authors say longer studies are needed [3]C.

A review notes a potential for serious harm from unapproved peptides, because human safety data are scarce [4]. More: Side effects and safety.

Interactions and who has no data

Because there are no human exposure data [2]regulator, nothing is known about interactions with other medicines in humans. For the same reason there are no data for pregnancy or breastfeeding, children or people with long-term illnesses.

Evidence against and what is unknown

There is little evidence against, because there are few studies at all. In a cell test, an effect was seen only with a TB-500 breakdown product, not with TB-500 itself [7]D.

Evidence against

• A 2024 study states that the biological effects of TB-500 had not been documented; earlier findings concerned the non-acetylated sequence [7]D.
• In rats, combining BPC-157 and TB-500 gave no added benefit over either substance alone [3]C.
• In an analysis by a French laboratory, the content of TB500 and TB1000 products bought online did not consistently match earlier descriptions [11]D.

What the evidence does not support

• "TB-500 is the same as thymosin beta-4": it is not. TB-500 is a seven-amino-acid fragment of it, and the form identified in analyses is acetylated Ac-LKKTETQ [2]regulator [5]D.
• "There are human studies of TB-500": the FDA has found no human exposure data [2]regulator.
• "It speeds up healing in humans": this rests on a rat tendon study and a mouse wound study [3, 8]C.
• "The vial always contains what the label says": the content of such products did not consistently match their descriptions [11]D, and according to Fimea an unauthorised product may contain a different substance than the packaging states [1]regulator.

TB-500 dosage in studies

No dose has been studied in humans, because there are no human exposure data [2]regulator. The only dose from a study that measured effects is from a rat study. In addition, in a doping-control method study horses were given one dose of a TB-500 product containing 10 mg of Ac-LKKTETQ [6]D. Neither is a recommendation, and an animal dose does not transfer to humans.

There are no doses studied in humans, so there is no dose page and no calculator preset. Doses of other substances: Dosing.

TB-500 vs thymosin beta-4: what is the difference?

They are different substances: thymosin beta-4 is a long protein, and TB-500 is a seven-amino-acid piece of it [2]regulator [5]D.

• Human studies: full-length thymosin beta-4 has been given to healthy volunteers in a phase 1 trial [9]A. There are no human data on TB-500 [2]regulator.
• Animal studies: in a mouse study the short LKKTETQ sequence worked in wounds comparably to full-length thymosin beta-4 [8]C.
• Sport: on the WADA list, thymosin beta-4 and its derivatives, for example TB-500, are in the same class S2.3 [13]regulator.

Combinations and blends

Combinations have not been studied in controlled human trials. In rats, combining BPC-157 and TB-500 gave no added benefit over either substance alone [3]C. The only human data are four patients who received knee injections of BPC-157 and thymosin beta-4 without a comparison group [10]B. More: BPC-157: what the research really shows.

Sellers declare TB-500 as a component of blends sold online, such as Wolverine and Glow. The declared composition has not been independently tested, and the rat combination study is not a study of these products [3]C. More: Peptide blends: what is in the vial and why the seller's label is not enough and all blends.

Status in the United States

In the United States, the FDA page lists TB-500 among substances that had been placed in compounding category 2 because of safety risks and whose nomination was later withdrawn by the nominator. The FDA risk assessment remains on the page (updated 22 Apr 2026) [2]regulator.

Is TB-500 legal in Finland?

TB-500 is listed in Annex 1 A of Fimea's medicines list [12]regulator. Annex 1 A substances are controlled as medicines in Finland and are always treated like prescription-only medicines. TB-500 has no marketing authorisation [14]regulator.

• Medicines list. In the Finnish medicines list (230/2025), TB-500 is named in annex 1 A, which covers medicinal substance analogues and prohormones classified as medicines [12]regulator.
• Marketing authorisation. On 12 Oct 2026 EMA's medicines data contained no medicine with thymosin beta-4 or TB-500 [14]regulator.
• Fimea warning, 29 June 2026. Fimea warned about injectable peptides bought online and gave TB-500 among its example names. Fimea advises not ordering injectable peptides from online shops or through social media, and buying medicines only from legal pharmacies [1]regulator.
• Import. Ordering medicines from outside the EU is covered on Peptides and the law in Finland. Bringing them back from a trip: Travelling with peptides.

This is not legal advice. Disclaimer.

Is TB-500 doping?

Yes. On the WADA 2026 Prohibited List, thymosin beta-4 and its derivatives, for example TB-500, fall under class S2.3 (growth factors and growth factor modulators). Class S2 substances are prohibited at all times, including out of competition [13]regulator.

Doping laboratories identify the main ingredient of TB-500, Ac-LKKTETQ, by mass spectrometry [5, 6]D, also in horse urine and plasma [6]D.

How to assess a TB-500 product

You cannot be sure what is in the product. According to Fimea, an unauthorised product may contain a different substance than the packaging states [1]regulator, and the content of TB500 and TB1000 products bought online did not consistently match earlier descriptions [11]D.

A certificate of analysis (COA) does not show a product is safe. For a certificate even to describe the content, it would need to identify the substance by mass spectrometry (MS), state the amount and purity, and refer to the same batch as the vial. Doping laboratories identify Ac-LKKTETQ precisely by mass spectrometry [5, 6]D. The FDA also points to peptide-related impurities and the potential of TB-500 to aggregate [2]regulator. More: How to read a COA and check a test result. Handling: Mixing and handling.

FAQ

Read the research yourself: sources

Every source opens the original publication or the regulator's page. The level shows what the source itself reports.

1. Fimea. Fimea warns: do not use injectable peptides purchased online (29 Jun 2026). Fimea regulator
2. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 22 Apr 2026). FDA regulator
3. Biçer 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;37:822-837. PMID 42542926 C
4. Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. 2026;56:1921-1935. PMID 41966639 (review)
5. Esposito 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;4:733-738. PMID 22962027 D
6. Ho EN, et al. Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta4, in equine urine and plasma by liquid chromatography-mass spectrometry. J Chromatogr A. 2012;1265:57-69. PMID 23084823 D
7. Rahaman 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 Analyt Technol Biomed Life Sci. 2024;1235:124033. PMID 38382158 C
8. Philp D, et al. 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 Regen. 2003;11:19-24. PMID 12581423 C
9. Wang X, et al. A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin beta4 in healthy Chinese volunteers. J Cell Mol Med. 2021;25:8222-8228. PMID 34346165 A
10. Lee E, Padgett B. Intra-Articular Injection of BPC 157 for Multiple Types of Knee Pain. Altern Ther Health Med. 2021;27:8-13. PMID 34324435 B
11. Delcourt V, et al. TB500/TB1000 and SGF1000: A scientific approach for a better understanding of misbranded and adulterated drugs. Drug Test Anal. 2023;15:458-464. PMID 36482504 D
12. Finland. Lääkeluettelo (Fimea medicines list), 230/2025, annex 1 A. Finlex regulator
13. World Anti-Doping Agency. 2026 Prohibited List. WADA regulator
14. European Medicines Agency. Medicine data (data set of 12 Oct 2026). EMA regulator

Research sources checked 12 Oct 2026. Regulator and registry sources checked 15 Sep to 12 Oct 2026.

Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.

Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.