Thymosin Beta-4
TB4Tβ4Thymosin β4Evidence
Clinical
Typical vial
2 mg
Route
2 routes
Status
United States
What it is
The full 43-amino-acid protein that TB-500 is a fragment of. It reached phase 2 trials in humans. TB-500 never has.
Thymosin beta-4 is the actual molecule. TB-500, which most people buy, is a synthetic fragment of it: a seven-residue section chosen because it keeps the actin-binding activity and costs a fraction as much to make.
That distinction cuts the opposite way to how it is usually presented. The full protein is the one with human clinical data: it was taken into phase 2 trials for dry eye disease, for pressure ulcers and for corneal wounds, under pharmaceutical development. The fragment sold as a research chemical has never been in a human trial at all.
So a page about thymosin beta-4 is partly a page about what TB-500 is not. If someone cites human trials as a reason to buy TB-500 — those trials were of this molecule — at doses and by routes that mostly were not injection into muscle.
How it works
Thymosin beta-4 is the main actin-sequestering protein in most cells. Actin is the scaffolding cells use to move, and by binding it, this protein regulates how readily cells migrate. That is the basis of its role in wound repair.
It promotes cell migration into damaged tissue, supports new blood vessel formation, and reduces inflammation. Those are three separate contributions to repair. That is why it attracted development attention.
The active site sits in a short central region, and that is the section synthesised as TB-500. Whether the fragment reproduces the whole protein's behaviour in a living body, as opposed to in an actin-binding assay, has not been established.
What it is studied for
Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.
Dry eye disease and corneal wounds
Clinical trialWhere the human trials actually were.
EvidencePhase 2 trials as an eye drop reported improvement in signs and symptoms. Development did not complete a registration programme.
Pressure ulcers and wound healing
Clinical trialStudied topically.
EvidencePhase 2 work in chronic wounds. Applied to the wound, not injected systemically.
Musculoskeletal injury
Community practiceWhy the fragment is bought.
EvidenceAnimal models only. No human trial has studied either molecule for tendon, muscle or ligament injury.
Regulatory status
Last reviewed 18 Aug 2026. Positions in this category change frequently, so we date the line.
Not approved anywhere. Reached phase 2 trials for ophthalmic and wound indications under pharmaceutical development, which did not proceed to registration. Sold as a research chemical, usually as the TB-500 fragment, not the full protein.
Identity and clearance
What the molecule is, and how long a dose stays measurable.
Molecule
- Class
- Actin-sequestering protein, naturally occurring
- Molecular weight
- 4963 Da
- Length
- 43 amino acids
TB-500 is a synthetic fragment of this molecule, not a synonym for it. The market blurs the distinction routinely.
Dose protocols reported in sources
Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.
| Goal | Dose | Frequency | Route | Units, 2 mg vial | Source | Start this protocol |
|---|---|---|---|---|---|---|
| Ophthalmic trial protocol | 100 mcg | Applied as an eye drop, twice daily | TopicalThe human trials used topical application to the eye or to a wound. Nothing about that transfers to a subcutaneous injection for a tendon. | 5 u | Clinical trial | Start this |
| Commonly described community protocol | 2 mg – 5 mg | Twice weekly during a loading phase, then weekly | SubcutaneousThe pattern described for TB-500 and applied to the full protein by extension. No trial supports either. | from 100 u | Community practice | Start this |
The doses above in syringe units, for the vial you have:
Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.
CheckRows marked community practice describe what people commonly do, drawn from public discussion. They are not derived from any trial and are not evidence that a dose is safe or effective.
Work out what to draw
Pre-filled with a 10 mg vial as a worked example. These are not recommended values — change them to match the vial in front of you.
Draw to 100 units on a 1 mL U-100 syringe. That is 1 mL, containing 5 mg of Thymosin Beta-4.
CheckThis fills the syringe almost to the top, which leaves no room for error when drawing.
BioAlmanac performs arithmetic on values you enter. It does not recommend doses, schedules or compounds, and nothing here is medical advice. Confirm every calculation against your vial and syringe before drawing, and speak with a licensed healthcare provider.
Open this calculation in the full calculator
Units, concentration, bacteriostatic water — the glossary defines the vocabulary, and a unit is not a fixed volume.
Safety
Reported effects, the situations that need care, and the ones that mean stop.
Reported effects
- Well tolerated in the ophthalmic trialsClinical trial
Documented
That record is for eye drops. It says nothing about repeated systemic injection.
- Injection site reactionsCommunity practice
Commonly reported
- Unquantified proliferative riskClinical trial
Unknown
It promotes cell migration and new blood vessel formation. Those are the same processes a tumour needs, and no study has looked at systemic administration in that context.
When to stop
- Any new lump, unexplained weight loss or unexplained persistent pain.
- Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care.
- An injection site that becomes hot, spreading or produces pus.
Interactions and situations that need care
- Active or previous cancerAvoid
Promoting cell migration and new blood vessel formation is what a tumour needs to grow and spread. No trial has examined systemic administration in someone with malignancy, and the mechanism points one way.
- Competing in a tested sportAvoid
Prohibited at all times under WADA's S2 category as a growth factor, and the fragment is treated identically.
- Pregnancy and breastfeedingAvoid
No reproductive or developmental safety data, for a protein that regulates cell migration during exactly the processes development depends on.
- Citing the human trials as support for injecting itUse caution
The phase 2 work was eye drops and wound dressings. Reading it as evidence for subcutaneous injection to heal a tendon is a change of molecule, route, dose and indication all at once.
SportProhibited by the World Anti-Doping Agency under S2: Peptide Hormones, Growth Factors, Related Substances, at all times, in and out of competition. Prohibited as a growth factor. The fragment is treated the same way.
What to expect
What the sources describe over time, and how confident anyone can be about it.
- This is the full protein. TB-500 is a fragment of it, and the two are not interchangeable however they are marketed.
- The human trials were eye drops and topical wound treatment, reaching phase 2 and stopping there.
- No human trial has studied either molecule for a musculoskeletal injury. Which is what almost everybody buys it for.
- It promotes new blood vessel formation, which is the basis of both the repair claim and the cancer concern.
- Prohibited in sport at all times.
Storage and combinations
How to keep it, and what it does and does not go with.
Storage and handling
- Freeze-dried powder
- Refrigerated at 2–8 °C, protected from light.
- After mixing
- Refrigerated at 2–8 °C. Do not freeze once mixed.
- Long-term, frozen
- Unopened powder is stable at −20 °C or colder.
With other peptides
- TB-500caution
TB-500 is a fragment of this molecule. Running both is taking the same activity twice, and the fragment has no human trial behind it while the full protein does.
- BPC-157synergistic
The most commonly described repair pairing, on the reasoning that one supports new blood vessels and the other cell migration. The mechanism is coherent and no controlled human study has tested the combination.
Checking your vial
Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it.
White cake, clear solution
Standard for a lyophilised peptide.
Collapsed cake or cloudy solution
Heat damage or degradation. Do not use it.
Vocabulary on this page
- Subcutaneous
- Into the layer of fat beneath the skin rather than into muscle. The route almost every peptide on this site uses.
- Research chemical
- A legal label, not a quality grade. It describes what a seller is permitted to sell you, and says nothing about what is in the vial.
- Evidence level
- The category of human evidence behind a compound, from preclinical through to approved. Stated on every profile here as a category, not an adjective.
- Stack
- Several separate compounds run at the same time, each in its own vial and on its own schedule.
- Injection site
- Where on the body an injection is given. Rotating between sites is standard practice for anything given repeatedly.
- Protocol
- One compound, with a dose, a frequency and a length: the plan, as opposed to what was actually taken.
Questions
- Is this the same as TB-500?
- No. TB-500 is a seven-residue fragment of this 43-amino-acid protein, chosen because it keeps the actin-binding activity and is far cheaper to make. The human trials belong to the full protein.
- Which should I buy?
- That question assumes evidence for injecting either, and there is none for musculoskeletal use. What can be said is that the clinical record people cite is for the full protein, applied topically.
References
Everything on this page that came from a source, with the source.
Thymosin beta-4 in ophthalmic and wound indications: phase 2 clinical programme
Ophthalmology and wound repair literature, 2015 · Randomised, placebo-controlled phase 2 trials
Adults with dry eye disease, corneal wounds or pressure ulcers · Topical application
Improvement in signs and symptoms against placebo in ophthalmic use, with good tolerability. Development did not proceed to a registration programme, and no trial studied systemic administration for musculoskeletal injury.
Commonly reported community protocols
BioAlmanac editorial summary of public community sources, 2026 · Not a study
Records dose and route patterns described in public discussion. Carries no evidential weight about safety or effect.
Thymosin Beta-4 compared with
BPC-157 vs Thymosin Beta-4
The two halves of the repair pairing, compared instead of combined. This is also where the TB-500 naming confusion does the most damage.
Thymosin alpha-1 vs Thymosin beta-4
They share a name and almost nothing else. One is an immune modulator with approvals in more than thirty countries; the other is a repair peptide still in trials. Sharing a prefix has done more harm here than in any other pair on this site.
Also compared with TB-500, GHK-Cu, KPV, LL-37, ARA-290, Thymulin.
Related compounds
TB-500
A synthetic fragment of thymosin beta-4, a naturally occurring protein involved in cell migration and tissue repair. Animal evidence only.
BPC-157
A synthetic 15-amino-acid peptide studied in animals for effects on tendon, ligament and gut tissue repair. No completed human trials.
GHK-Cu
A naturally occurring copper-binding tripeptide with a long history in topical skincare research. Injected use is not what the research studied.
KPV
A three-amino-acid fragment of alpha-MSH studied for anti-inflammatory effects, largely in animal models of gut inflammation.
Next
What to do with Thymosin Beta-4
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. Thymosin Beta-4 is filled in for you.
- See what it costsPer-milligram prices read from vendor sites and confirmed by a person, so vial sizes compare.
- Check a combinationWhat our profiles record about Thymosin Beta-4 alongside each other compound — including the pairs where nothing is recorded.
Keep this page honest
If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on BioAlmanac is medical advice. No clinician reviews these pages.
Page last updated 18 Aug 2026