TB-500 is a synthetic peptide made from a 7-amino-acid piece of thymosin beta-4, a natural protein that helps cells move and repair tissue.[1] It is marketed for injury recovery and often sold with BPC-157. FDA found no studies in which TB-500 was given to people and no animal toxicity studies, and it is not FDA-approved.[4]
This profile explains what TB-500 is, how it differs from thymosin beta-4, what animal and human research shows, side effects, dosage and its 2026 regulatory status.
What is TB-500?
TB-500 contains the acetylated 17-23 fragment of thymosin beta-4, with the sequence Ac-LKKTETQ.[1] That stretch is the protein’s active site for binding actin, a building block of the cell’s internal skeleton. TB-500 was first described as a veterinary product, and doping labs developed tests for it in racehorses.[2]
TB-500 vs thymosin beta-4
| Thymosin beta-4 | TB-500 | |
|---|---|---|
| What it is | Natural 43-amino-acid protein[10] | Synthetic 7-amino-acid fragment[1] |
| Human trials | Several, as eye drops, skin gel and IV[7][10][12] | None[4] |
| Approved anywhere? | No | No |
Much of what is said online about TB-500 actually comes from studies of full-length thymosin beta-4. Those results do not automatically carry over to the fragment.
How TB-500 works
The actin-binding fragment is thought to drive many of thymosin beta-4’s repair effects. In aged mice, a peptide containing this fragment promoted wound repair comparable to the full protein.[3] In a lab scratch test on skin cells, however, TB-500 itself did not speed “wound” closure.[4] A 2024 Korean study found that of TB-500 and its breakdown products, only one fragment (Ac-LKKTE) showed significant wound-healing activity in cells, suggesting earlier results may reflect a metabolite rather than TB-500 itself.[22]
TB-500 benefits: what the research shows
In animals
- Wound repair: the fragment sped skin healing in aged mice.[3]
- Tendon healing: in a 2026 study in Türkiye, TB-500 significantly increased the strength of repaired Achilles tendons in rats.[6]
In people
There are no published human studies of TB-500.[4] Full-length thymosin beta-4 has been tested in people:
- Dry eye: in a 9-patient phase 2 trial, thymosin beta-4 drops reduced eye discomfort by 35.1% and corneal damage by 59.1% more than inactive drops.[7] A larger 72-person trial missed its main goals but improved some secondary measures.[8]
- Eye surface healing: in a small phase 3 trial for neurotrophic keratopathy, 6 of 10 eyes on thymosin beta-4 healed completely at 4 weeks versus 1 of 8 on placebo, a difference that did not reach statistical significance.[9]
- Leg ulcers: a topical gel tested in Italy and Poland was as safe as placebo and may have sped healing.[10] In two phase 2 trials, it sped healing by almost a month in patients whose wounds did heal.[11]
TB-500 and BPC-157 together
TB-500 and BPC-157 are the most common peptide pairing for injuries, and both are in the GLOW and KLOW blends. The only study of the combination, in rats with Achilles repairs, found that combining them gave no additional benefit over either alone.[6] See our BPC-157 profile for that peptide’s evidence.
What users report
TB-500 research around the world
- Italy and Poland: topical thymosin beta-4 was tested for venous leg ulcers at eight sites.[10]
- China: a recombinant form of thymosin beta-4 was well tolerated in a 2021 phase 1 trial in healthy volunteers.[13] In a 2025 trial in 96 heart attack patients, it did not significantly reduce heart damage overall, though it did in patients treated within 8 hours.[25]
- South Korea: the doping control lab that studied how TB-500 breaks down in the body.[22]
- France: a horse-racing lab found online TB-500 products often did not contain what their labels claimed.[23]
- Türkiye: the only animal study combining TB-500 and BPC-157.[6]
- Hong Kong and Italy: doping-control labs developed methods to detect TB-500 in horses and humans.[1][2]
TB-500 side effects and safety
- No human data: side effects of TB-500 in people are unknown. FDA found no adverse event reports for it, but notes that absence of reports does not mean it is safe.[4]
- No toxicity studies: FDA identified no animal toxicity studies of TB-500.[4]
- Reported case with BPC-157: FDA described a report of skin and gum darkening that recurred when a person used BPC-157 with TB-500 again; the cause was unclear.[4]
- Theoretical cancer concern: reviews describe beta-thymosins, including thymosin beta-4, as involved in tumor spread, and a 2026 review lists cancer among the potential risks of unregulated healing peptides. These risks are theoretical, not observed with TB-500.[14][21]
- Product quality: FDA’s main concern is immune reactions from impurities or clumped peptide.[15] A lab analysis of online “TB500” and “TB1000” products found their contents were not consistently what the labels described.[23]
TB-500 dosage: what has been studied
No dose of TB-500 has been studied in people.[4]
| Setting | Dose |
|---|---|
| Horses (pharmacokinetics) | 10 mg under the skin; blood levels peaked at 1 to 2 hours and were gone by 6 to 10 hours[4] |
| Rats (tendon study) | 60 mcg per kg per day for 4 weeks[6] |
| Full-length thymosin beta-4 (not TB-500), healthy humans | 42 to 1,260 mg by IV[12] |
For converting milligrams to syringe units, see our peptide calculator.
Is TB-500 FDA approved or legal?
- Not FDA-approved and not part of any approved drug.[4]
- 2023: FDA listed the thymosin beta-4 fragment among substances that may pose significant safety risks in compounding.[15]
- April 2026: after the nomination was withdrawn, FDA removed it from that list, which is not an approval.[15][16]
- July 2026: FDA reviewed TB-500 for wound healing and recommended against it, but its compounding advisory committee reportedly voted 8 to 6 in favor.[17][5][18] The vote is not binding, and no rule had followed as of our last review.
- Banned in sport: WADA prohibits thymosin beta-4 and derivatives such as TB-500 at all times.[19] In horse racing, an Australian trainer was banned for eight months in 2016 after injecting a horse with a thymosin beta-4 derivative called TB-1000.[24]
This is general information, not legal advice.
TB-500 vs BPC-157
Both are marketed for injuries, but they are unrelated molecules. BPC-157 is a 15-amino-acid peptide based on a stomach protein, with a few small human pilot studies; TB-500 is an actin-binding fragment with none. Read our BPC-157 profile for a full comparison of the evidence.