TB-500 is the second-most-talked-about recovery peptide in the strength community. It's the peptide that gets added to a BPC-157 stack when local injection isn't moving the needle on a stubborn tendon or ligament problem.
This guide explains what TB-500 actually is, how it differs from full thymosin beta-4, how people dose it, the BPC-157 stack rationale, and where to be skeptical.
What TB-500 actually is
TB-500 is a synthetic peptide — a 17-amino-acid fragment of the full thymosin beta-4 (TB4) protein. TB4 is found in nearly every tissue in the body, where it plays roles in:
- Actin sequestration — TB4 binds and regulates G-actin, the building block of the cytoskeleton
- Cell migration — directing immune cells, endothelial cells, and stem cells to sites of injury
- Anti-inflammatory signaling — modulating the local environment around damage
TB-500 is the central active fragment of TB4, isolated to make manufacturing simpler and cheaper. It contains the actin-binding domain but is a fraction of the size of the parent protein.
TB-500 vs full thymosin beta-4
This distinction matters more than most people realize:
| Property | TB-500 (fragment) | Full TB4 |
|---|---|---|
| Length | 17 amino acids | 43 amino acids |
| Cost to manufacture | Low | High |
| Actin binding | Retained | Retained |
| Peptide signaling beyond actin | Lost | Retained |
| Availability | Widely sold as research chem | Mostly research-only / clinical supply |
When studies and vendors refer to "TB-500," they almost always mean the fragment. When peer-reviewed literature on cardiac repair, corneal healing, or stroke recovery discusses "thymosin beta-4," they almost always mean the full protein. Pre-clinical research on the parent protein doesn't always translate cleanly to the fragment — keep that in mind when reading marketing copy.
What the research says
Like BPC-157, TB-500 has solid pre-clinical data and limited human trial data. The strongest signals are in:
- Skeletal muscle injury recovery (rodent models)
- Tendon and ligament healing
- Corneal wound healing
- Cardiac tissue regeneration after myocardial infarction (full TB4, not the fragment)
- Hair follicle stimulation (some clinical interest)
There is no FDA-approved indication. The strength community's use is driven by N-of-1 reports plus the pre-clinical record on the actin-binding mechanism.
How TB-500 is typically dosed
TB-500 has a long tissue half-life, so it isn't dosed daily. The two-phase pattern most commonly reported:
| Phase | Dose | Cadence | Duration |
|---|---|---|---|
| Loading | 2–5 mg | Twice weekly | 4–6 weeks |
| Maintenance | 2–5 mg | Every 1–2 weeks | As needed |
For specific protocols and how dose scales with body weight, see TB-500 dosing protocols.
The BPC-157 + TB-500 stack
This is the pairing the recovery community is built around. The rationale:
- BPC-157 acts mostly locally — angiogenesis, VEGF/FGF/TGF-beta upregulation, and gut barrier protection. Best when injected near the injured tissue.
- TB-500 acts mostly systemically — actin reorganization and stem-cell migration, with a long tissue half-life. Best for whole-body or hard-to-pinpoint injuries.
For a chronic Achilles or rotator-cuff issue, the stack reportedly outperforms either peptide alone. For a fresh, well-localized strain, BPC-157 alone is often enough.
Full breakdown: BPC-157 vs TB-500 and how to stack them.
Reconstitution math
TB-500 ships lyophilized. The standard mix:
5 mg vial + 2 mL BAC water = 2.5 mg/mL. A 2.5 mg dose is then 1 mL — or 100 units on a U-100 insulin syringe.
A 5 mg dose at this concentration won't fit in a single insulin syringe — you'd split it across two injections or reconstitute more concentrated. The reconstitution calculator flags this automatically.
Side effects and safety profile
TB-500's reported side effects are similar to BPC-157's — generally mild:
- Lethargy or "flu-like" feeling for a day or two after a loading dose
- Mild headaches
- Injection-site reactions
- Occasional reports of transient blood-pressure changes
The same theoretical cancer concern applies: TB-500 promotes cell migration and angiogenesis, so most users avoid it with any active or recent cancer history. This is a theoretical concern in animal models, not a confirmed human signal — but it's the right place to be cautious.
Deeper coverage: TB-500 side effects.
Legal status
Like BPC-157, TB-500 is not FDA-approved for human use. Unlike BPC-157, it has not yet been formally rejected for compounding — but in practice, almost all TB-500 in circulation is research-chemical-grade. The same vendor-quality and purity caveats apply.
Who should and shouldn't use TB-500
Most-fitting use cases (per reported experience):
- Stubborn whole-body recovery issues — chronic tendinopathy, multiple overlapping soft-tissue strains
- Athletes with recurring small injuries that never fully resolve
- Adjunct to BPC-157 for difficult cases
Least appropriate:
- Anyone with active or recent cancer
- Acute, well-localized injuries where BPC-157 alone is reportedly sufficient
- Users uninterested in twice-weekly injection logistics