Question 1

What is TB-500?

Accepted Answer

TB-500 is a laboratory-made piece of a protein the body already makes for itself, and the gap between that piece and the whole protein, thymosin β4, runs through this entire page. A 2026 sports medicine review lists the two as separate entries: Tβ4 (thymosin beta-4), and TB-500 (thymosin beta-4 fragment). The clinical trial registry is more exact again, naming the molecule under study as the Thymosin Beta 4 17-23 Fragment, which is a run of seven amino acids cut out of a considerably longer protein. Elsewhere the two names are treated as interchangeable: a 2026 scoping review of six compounds sold for recovery lists its subject as thymosin beta-4 or TB-500, a single item carrying two labels. That shorthand is ordinary in the literature, and it is why a reader finds randomised heart-attack trials attached to something sold in a vial as a fragment.

Question 2

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

Accepted Answer

No. One is a short fragment and the other is the full protein, and the research behind each is very unevenly divided. A 2007 review traces the development of thymosin beta(4) from a thymic hormone to an actin-sequestering peptide and back to a cytokine supporting wound healing, and nearly everything below was measured on that whole molecule rather than on a piece of it. Fragments do get studied on their own, and the results do not transfer between them. A 2025 zebrafish experiment built five short peptides from their precursor proteins, one of them thymosin beta-4, and tested each separately. Cell viability by the MTT assay indicates that all five peptides are not cytotoxic in all concentrations tested in both mouse and human cell lines. That was a different cut from the one sold as TB-500, which is the point: a protein can be cut in many places, and each piece is its own molecule. So a result obtained with the full protein is not automatically a result for the fragment.

Question 3

Does TB-500 actually work?

Accepted Answer

A 2026 scoping review went looking for exactly this across six compounds. Its first finding is about the shape of the work rather than the effect. Of the publications it identified, 67% used preclinical animal models. On the animal side it reports promising but variable effects on tendon, muscle, bone, and ligament healing, most commonly rats. On the human side, human clinical studies were limited to a handful of investigations, most lacking robust controls or rigorous study designs. Its conclusion is plain: the claimed benefits remain unsubstantiated by current human trials. One area is stronger than that, though not the one most buyers want. A 2016 review reports that Tβ4 also accelerated the rate of repair in phase 2 trials with patients having pressure ulcers, stasis ulcers, and epidermolysis bullosa wounds. The last of those is a rare inherited blistering condition. Those were trials of the whole protein on open skin, rather than a fragment injected for a torn tendon. A 2026 review names one more factor: the placebo effect as a mediator of peptide efficacy.

Question 4

Has TB-500 been tested in people?

Accepted Answer

Thymosin β4 has been, repeatedly. TB-500 as a named molecule has one registered study and no published result. The registry holds a run of trials, all of the protein. A Phase 1a Study of Thymosin Beta 4 in Healthy Volunteers and a Phase 1b study of the same design are both listed as COMPLETED. Two Phase 2 studies in heart-attack patients are also completed, and a third, Recombinant Human Thymosin Beta 4 for Injection(NL005) for Acute Myocardial Infarction, has not started. An earlier Phase 1 study of intravenous dosing in volunteers is marked WITHDRAWN. One cardiac study has published, and it points two ways. In a randomized, placebo-controlled, double-blind trial involving 96 STEMI patients, meaning people who had just had a major heart attack, the damaged areas were smaller in the group dosed within eight hours. Then comes the limit: However, the overall differences in infarcted areas were not significantly between the rhTB4 group and the placebo group (n = 96). A subgroup moved and the whole trial did not. The one entry naming the fragment is TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD, listed as RECRUITING. It measures blood markers rather than recovery from an injury.

Question 5

Does TB-500 affect testosterone?

Accepted Answer

No study among the research behind this page has measured testosterone, oestrogen or any other sex hormone in a person given TB-500 or thymosin β4. The question comes from the name: thymosin was first pulled out of the thymus and described as a thymic hormone, and a word like that sounds as though an endocrine claim is attached to it. The literature withdrew that description decades ago. A 2007 review of the family says outright that none of the isolated peptides were really thymic hormones, and that they are all biological important peptides with diverse functions. What the protein does instead is bind actin, the filament a cell builds and takes apart in order to move, and beta-Thymosins are the main intracellular G-actin-sequestering peptides in most vertebrate cells. Read that as a correction to a false lead from a name, rather than a measurement pointing either way. A missing hormone claim is not the same as a blood test showing nothing changed, and no study we could find drew blood from a person using this compound, so the question has not been asked.

Question 6

How does TB-500 make you feel?

Accepted Answer

No study among the research behind this page has recorded how a person feels while using TB-500. These trials were not designed to capture subjective experience, and it surfaces in only two small, local places. The first is a 2010 report on the results of nine patients (ages 37-84) with chronic nonhealing neurotrophic corneal epithelial defects, meaning long-standing wounds on the surface of the eye. They were given thymosin β4 as drops, and reduced ocular irritation was reported by all patients soon after treatment initiation. That is a treated eye becoming more comfortable, rather than anything systemic. The second is a 2021 chart review of knee injections, where patients were asked to rate their pain prior to injection, the length of time the peptides helped ease the pain and the degree to which the injection helped them. Only four of the sixteen people surveyed had received thymosin β4, and they received it mixed with BPC-157, so nothing in those answers can be assigned to one compound rather than the other. So the record holds two accounts of a treated body part feeling better, and nothing about mood, energy or sleep.

Question 7

What does TB-500 do to the body?

Accepted Answer

Everything here describes the full protein, and almost all of it was measured in animals or in cultured cells. The clearest account is a 2012 paper on the molecule's basic biology. After injury, thymosin β(4), is released by platelets, macrophages and many other cell types, and the protein binds to actin and promotes cell migration. The same paper reports that thymosin β(4) also decreases the number of myofibroblasts in wounds, resulting in decreased scar formation and fibrosis, a myofibroblast being the cell that contracts a healing wound and pulls a scar tight. Two further roles sit outside tissue repair. A 1992 review of what holds back blood-cell production lists acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) or thymosin-beta 4 among those factors. A 2024 mouse study found the protein among three peptides released by a small gland in the brain, where putting them back rescued developmental defects in animals whose gland had been removed. Cell movement, scarring, blood cells and brain development is not one job. It reads as general housekeeping machinery, which is why the animal list runs long and why a dose in an uninjured body is hard to predict.

Question 8

How long does TB-500 take to work?

Accepted Answer

No study among the research behind this page has measured onset in a person given TB-500. What exists instead is the length of the windows researchers chose for their own experiments, a different measurement that does at least bracket the question. In cultured cells the response is quick and dose-related: a 2020 study reports that Tβ4 enhanced HCEC proliferation and migration in a dose- and time-dependent manner, in human corneal cells read over hours rather than weeks. In animals the windows run to days, since a 2025 cardiac study gave mice a 7-day rhTB4 treatment and then read the outcome 28 days post-I/R surgery, and a 2023 Alzheimer's study dosed mice once daily for 6 days. In people the only durations on record come from the corneal series, where patients used thymosin β4 eye drops for 28 or 49 days with a follow-up period of 30 days. So the designs that produced these results ran for weeks, and none was built to catch the moment a person first notices something. When a researcher stops dosing and when an effect begins are different questions. The amounts that filled those windows, and the animals they were measured in, belong to the TB-500 dosage page, because a schedule without a quantity settles very little.

Question 9

Is TB-500 effective taken orally?

Accepted Answer

No study among the research behind this page has given TB-500 or thymosin β4 by mouth, so there is no oral result to report in either direction. Every documented route used a needle, or went straight onto the tissue being studied. Pregnant mice in a 2021 study were weighed and treated with an intraperitoneal injection of TB4, which means into the belly cavity, and a 2023 brain study gave mice Tβ4 (5 mg/kg, i.v.) or PBS, a shot into a vein. A 2017 gut study worked intracolonically to mediate the secretory expression of Tβ4 in mouse colons, the eye work used sterile eye drops, and the one human knee study used intra-articular injection of the peptide BPC 157, alone or combined with TB4, meaning into the joint space. Read that list as a pattern rather than a verdict on swallowing. Researchers put the protein where they wanted it and skipped the gut, and whether an oral dose survives digestion is a question nothing in these sources tested.

Question 10

Does TB-500 affect the heart?

Accepted Answer

This is the one place a human result exists at all, and every part of it used the full protein. A 2025 study ran both halves of the question in one paper. In C57BL/6J mice, 7-day rhTB4 treatment prevented cardiac dysfunction and fibrosis 28 days post-I/R surgery, I/R meaning the damage done when blood flow is cut off and then restored. In a permanent ligation model, rhTB4 improved cardiac function and reduced infarct size at 8 weeks post-MI in the same mice. The human arm is the 96-patient randomised trial described above. The authors read their own result carefully: further rigorous randomized studies are needed to assess the significance of early rhTB4 use post-myocardial infarction reperfusion. Two more Phase 2 trials in heart-attack patients are registered, so somebody is asking this properly. None of that says what a fragment does to a heart that has not had a heart attack. These are repair signals in damaged tissue, measured in mice and in people during a medical emergency, and that is a different question from steady use in a healthy adult.

Question 11

Can dogs take TB-500?

Accepted Answer

No study among the research behind this page has given TB-500 or thymosin β4 to a dog, and no veterinary amount, route or schedule appears anywhere in this literature. The species on record are small laboratory animals. A 2025 cardiac study used C57BL/6J mice, a 2023 brain study used 12.5-month-old male APP/PS1 mice and their WT littermates, and a 2021 pregnancy study reported that 10 pregnant mice received the same injection regimen. A 2025 Parkinson's experiment used a 6-OHDA zebrafish larvae model, and a 2016 bone experiment used mouse bone marrow-derived macrophages. Those species were picked for laboratory convenience, rather than as stand-ins for a thirty-kilo animal dosed at home, and nothing in that list sets an amount, a route or a length of course for a dog. Body size and how long a protein lasts in the blood both differ, and those are the things that govern exposure.

Question 12

Is TB-500 legal? Is it approved?

Accepted Answer

Not approved by any regulator, for any use, and the record explains why rather than describing a rejection. A 2026 sports medicine review places it inside a parallel "gray market" of unapproved compounds has emerged, operating largely outside of regulatory oversight. It lists the compound by both names, among eleven other peptides marketed direct to patients. A 2026 scoping review lands in the same place: peptide supplements should not currently be recommended as a replacement or adjunct for existing orthopaedic standard of care. The full protein has been through real trials and still carries no licence. Two Phase 1 studies in healthy volunteers are completed, and two Phase 2 cardiac studies are completed, which is further than most compounds in this category travel. Separately, the FDA's recall records hold four entries for compounded thymosin beta-4 injections. The 2019 entry gives its reason as Lack of sterility assurance, and the later ones as Lack of Assurance of Sterility. That describes how a pharmacy filled a vial, not the molecule inside it. One of the four covers a combined BPC-157/Thymosin Beta-4 for Injection. All four are set out on the safety page.

Question 13

Is TB-500 safe?

Accepted Answer

No study among the research behind this page has measured what happens to a person using TB-500 over months. The most specific statement available comes from a 2026 review of this market, which reports that rigorous human safety data are scarce, and there is potential for serious harm to patients. That covers unapproved peptides as a group rather than this one alone, and it is still the closest thing to a safety summary anyone has written. What does exist belongs to the protein. A Phase 1b Study of Thymosin Beta 4 in Healthy Volunteers is listed as completed and two cardiac trials carry safety in their titles, but none of those results reaches a fragment injected for a sports injury. The 2026 scoping review names the gap directly: these compounds are often perceived as low risk, despite the absence of efficacy or safety data for many emerging peptides. Documented adverse effects, daily use, interactions, who was excluded and the four FDA recall records all have their own entries on the TB-500 safety page.

Question 14

How does TB-500 work?

Accepted Answer

The proposed mechanism is about cell movement rather than tissue growth. Thymosin β4 binds actin, the filament a cell builds and takes apart in order to crawl. A 2007 review describes the protein as modulating the availability of actin monomers in a large variety of cells. Adding it from outside alters the actin cytoskeleton, and has multiple effects on cellular functions related to motility. A 2012 paper restates that in repair terms: the protein binds to actin and promotes cell migration, including the mobilization, migration, and differentiation of stem/progenitor cells. The signalling underneath has been mapped in two settings. A 2020 eye study tied the effect to increased ATP levels, P2X7 R-mediated Ca2+ influx, and the ERK1/2 signaling pathway in human corneal cells. A 2025 heart study found that rhTB4 activated the ErbB2/Raf1 signaling pathway, and blocking that receptor abolished the effect in mice. Two limits are worth keeping. The 2007 review says that very little is known about molecular mechanisms mediating the effects attributed to extracellular beta-thymosins. And every mechanism above was worked out on the whole protein, so how the seven-amino-acid fragment binds anything has not been published.

TB-500