TB-500 Dosage, Side Effects & Legal Status
TB-500 is sold as a synthetic fragment of thymosin beta-4, a naturally occurring protein involved in cell migration and wound repair. Most of the published wound-healing evidence is for full-length thymosin beta-4, not the shortened TB-500 fragment specifically, which is an important distinction vendors rarely make.
Reviewed by the PepGuard team · Last reviewed Jul 28, 2026
Synthetic fragment of Thymosin Beta-4 (actin-binding region) · also sold as Thymosin Beta-4 fragment, TB4 fragment 17-23
Photo: Abdulai Sayni / UnsplashWhat the literature and self-reports actually say.
| What's cited | Range |
|---|---|
| Commonly cited loading dose | 2-2.5 mg, twice weekly |
| Commonly cited loading phase length | 4-6 weeks |
| Commonly cited maintenance dose | 2-2.5 mg, once weekly |
| Commonly cited weekly total | 2-5 mg/week across sources |
No human trial has established a validated dose for TB-500 specifically. The figures below are what's most frequently cited in non-clinical and vendor-reported protocols, presented for informational comparison only, not as a recommendation. The calculator further down this page converts the loading or maintenance dose above into an exact draw volume for your vial size.
Signal strength, not just a list.
How often each effect shows up in the available sources, and how solid that evidence actually is.
| Signal | Frequency | Context |
|---|---|---|
| Injection site reaction | commonly reported | General to subcutaneous/intramuscular injection, not unique to TB-500. |
| Fatigue or lethargy | occasionally reported | Anecdotal self-reports only; not measured in a controlled TB-500 human trial. |
| Headache or flushing shortly after injection | occasionally reported | Anecdotal; no dose-response data exists for TB-500 specifically. |
| Effects on cancer risk or cell proliferation regulation | unknown / not studied | Actin-binding peptides that promote cell migration are a theoretical area of caution raised in review literature; not established as a risk in humans, not ruled out either. |
Not FDA-approved. Unapproved research compound.
TB-500 has never been approved by the FDA for human use. Full-length thymosin beta-4 has been studied in human trials for an unrelated ophthalmic indication under a separate regulatory track, but that does not extend to TB-500 as sold by research-peptide vendors. Its compounding bulk-substance status is subject to the same kind of periodic FDA review as BPC-157: at a July 23, 2026 PCAC meeting, FDA staff recommended against adding TB-500 to the 503A compounding list, but the advisory panel voted, by a narrow margin and against that recommendation, in favor of it anyway, per independent reporting from NPR and CBS News. That's an advisory recommendation, not an FDA decision, and the FDA hasn't yet acted on it. Treat any "it's fine, it's legal" claim as time-stamped, not permanent.
Every claim above, traced back.
Primary studies, reviews, regulatory pages, and trial registries. Click through and check them yourself.
TB-500 questions, answered.
No, not exactly. TB-500 is sold as a shortened synthetic fragment of the full thymosin beta-4 protein. Most of the peer-reviewed wound-healing evidence was produced on the full-length protein, not the fragment sold as TB-500, so applying that evidence to TB-500 is an extrapolation, not a direct finding.
It hasn't been studied in a controlled human trial under that name. What exists is animal and cell-culture evidence for the parent protein, plus anecdotal self-reports for the fragment. That's a meaningfully thinner evidence base than a lot of marketing copy implies.
It's sold in the US as a "research use only" chemical, not as an approved drug or supplement for human use. Its status on the FDA's compounding bulk-substance list is reviewed periodically and has shifted before, so check current status rather than relying on an older claim.
TB-500 is typically sold as a lyophilized powder that needs to be reconstituted with bacteriostatic water before it can be drawn into a syringe. The calculator on this page turns a vial size, water volume, and target dose (like the loading or maintenance figures above) into an exact draw volume and syringe unit reading, it does the arithmetic only, not a recommendation on which dose to use.
Keep researching.
This is a preview of the TB-500 report.
Create your account to check any peptide against the full research base.