TB-500

What is TB-500? Definition and origin of the peptide

TB-500 is a lab-made fragment of a protein your body already produces, called Thymosin Beta-4 (Tβ4). In medical research, it is mainly studied for its potential to help tissue repair. As a pure research chemical, TB-500 has no pharmaceutical approval and is strictly banned in sports. Originally, the company Regeneron developed the full Thymosin Beta-4, which has 43 amino acids, for horse racing to speed up the recovery of racehorses. On the gray market, the name TB-500 today usually refers to a short fragment of 7 amino acids (sequence Ac-LKKTETQ), because it is cheaper to produce than the full protein.

Important: TB-500 (the fragment) and Thymosin Beta-4 (the full protein) are often confused, even by vendors. Most scientific human studies refer to the full protein Tβ4, not the isolated fragment. The biological effect of the short TB-500 fragment in humans has not been documented so far [4, 11].

Using TB-500: Injection forms and practice

On the gray market, TB-500 is almost exclusively given as a subcutaneous injection into the belly fat or the thigh. However, this way of taking it is not backed by clinical human studies. In fact, no published study has looked at subcutaneous injection of the TB-500 fragment in humans. The common gray-market practice is based only on anecdotal reports and on extrapolating data from animal studies [11].

In clinical studies with the full Thymosin Beta-4, on the other hand, other routes of administration were chosen: topical for skin or eye conditions, and intravenous in heart attack studies. These data cannot be directly applied to the TB-500 fragment. In horse sports, TB-500 was mostly given intramuscularly at 10 mg per injection [11]. There are also FDA-documented but unapproved nasal sprays and local applications.

Mixing TB-500: Guide to reconstitution and dosing

TB-500 is usually sold as a freeze-dried powder (lyophilisate) in vials with 2, 5, or 10 mg of active ingredient. Before use, the peptide powder must be dissolved, which is called reconstitution. For this, bacteriostatic water (BAC water) is used, because it stays germ-free thanks to preservatives.

Worked example (unverified user practice):

• Vial: 5 mg TB-500 powder
• Reconstitution: Adding 2 ml of BAC water gives a concentration of 2.5 mg/ml
• Target dose: For 2.5 mg, you draw up 1 ml of solution (equals 100 units on an insulin syringe)

With a 10-mg vial and 2 ml of BAC water, the concentration is 5 mg/ml; for a dose of 2.5 mg, you would draw up 0.5 ml (50 units). You can find detailed information on mixing and storage in the guides on handling peptides, whose principles also apply to TB-500.

Reconstituted vials should be stored in the fridge at 2-8 °C and used up within about 28 days. Before buying, you should also read up on protection when ordering and safety measures, because products on the gray market are often mislabeled or contaminated.

Effects of TB-500: Biological mechanisms

TB-500 is a protein fragment synthesized in the lab that is supposed to support the body's natural self-healing. The mechanism of action is based on binding to the cell skeleton (actin). TB-500 binds monomeric G-actin building blocks and keeps them ready for building new cell structures, a process called G-actin sequestration. In theory, this could promote cell migration, the formation of new blood vessels (angiogenesis), and anti-inflammatory processes.

Compared to the full Thymosin Beta-4, however, the TB-500 fragment lacks important functions, such as influencing DNA polymerase for cell division. Whether the fragment actually achieves the same regenerative effects as the parent molecule is not scientifically proven in humans.

Effectiveness: Study situation on TB-500 and Thymosin Beta-4

The scientific evidence for the effectiveness of TB-500 in humans is extremely limited. There are no completed, controlled clinical studies on the isolated TB-500 fragment; the existing evidence is limited to in-vitro tests and animal studies [4, 11].

Human studies focus almost exclusively on the full Tβ4 molecule. For Tβ4, there is a phase 1b study in healthy people as well as phase II studies on myocardial infarctions, venous ulcers, and pressure sores. However, these results cannot be transferred one-to-one to the shorter TB-500 fragment.

A review from 2026 states that unauthorized peptide therapies like TB-500 for treating injuries or for performance enhancement are not supported by solid human studies [11].

TB-500 dosage: Protocols from user practice

Since clinical studies are missing, there is no medically validated dosage for TB-500. The schemes circulating in forums and on the gray market are based on anecdotal experiences and on extrapolating animal data, not on solid clinical research.

Some users use weight-based protocols with about 30-60 µg/kg per injection in the loading phase. These figures are not clinically validated and come primarily from gray-market vendors and community discussions [11]. The FDA only documents the existence of unapproved products like nasal sprays (10 mg/25 ml) or injection solutions (10 mg).

In the phase 1b study with the full Tβ4, intravenous doses of 0.43-5.25 mg/kg were used, but these cannot be applied to subcutaneous use of the fragment.

Side effects and risks of use

The side effect profile of TB-500 is insufficiently researched, because there is no approval as a drug. Reported effects include reactions at the injection site, headaches, fatigue, and performance fluctuations. The FDA explicitly warns about safety risks with TB-500, since there is no data on human exposure. The substance has also been added to a list of bulk substances that carry significant risks when compounded.

• Confusion of TB-500 (fragment) with the full Thymosin Beta-4 due to mislabeling
• Reconstitution with saline solution instead of BAC water, which can cause the peptide to precipitate
• Incorrect storage at room temperature instead of in the fridge after mixing
• Dangerous overdose due to missing safety data

Legal status and WADA regulations in Germany and the EU

TB-500 has no approval as a drug in Germany and the EU (BfArM/EMA) or in the USA (FDA). It is classified as an unregulated research chemical and is not approved as a dietary supplement. While the parent molecule Tβ4 has FDA orphan drug status, there is no formal approval for humans.

TB-500 is listed on the WADA prohibited list under category S2 (peptide hormones and growth factors) and is strictly banned in competitive sports and in horse sports [1, 9]. In Germany, mere possession by private individuals is not a criminal offense, but selling it as an unapproved drug is illegal.

You can find more information on related substances in the comprehensive peptide library.