TB-500
Thymosin beta-4 fragment · TB4 fragment
Thymosin beta-4 is a real protein found throughout the body, with a well-described role in binding actin, the structural filament cells use to change shape and move. TB-500 is not that protein: it is a short synthetic fragment of it, sold on the reasoning that the fragment carries the repair-relevant activity.
That distinction matters when reading claims about it, because research on full-length thymosin beta-4 is frequently cited as though it were research on TB-500. Evidence specific to the fragment is thinner, and as with BPC-157 it is preclinical. No controlled human trial supports its use for injury recovery.
How it works
Thymosin beta-4 sequesters actin monomers, which influences how readily cells reorganise their internal structure and migrate. In wound healing, cells have to move into the damaged area before they can rebuild it, so a protein that promotes migration is a plausible repair signal.
In animal models the protein has also been associated with new blood vessel formation and with reduced inflammatory signalling at injury sites. Whether the synthetic fragment reproduces these effects at the doses people use is not established.
Regulatory status — United States
Not approved for human use in the United States. Sold only as a research chemical, with no manufacturing standard behind that label.
Last reviewed 12 Aug 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.
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.
Soft tissue and tendon repair
Published reviewThe most commonly discussed use.
EvidenceAnimal models of muscle and tendon injury, mostly using full-length thymosin beta-4, not the fragment sold as TB-500.
Wound healing
Published reviewDiscussed for dermal and corneal wound repair.
EvidenceAnimal and early clinical work exists on full-length thymosin beta-4. It does not transfer automatically to the fragment.
Identity and clearance
Molecule
- Class
- Synthetic fragment of thymosin beta-4
- Molecular weight
- 889 Da
- Length
- 7 amino acids
Sequence
Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln
The actin-binding region of the 43-amino-acid parent protein. Material sold as TB-500 varies between suppliers, and some is full-length thymosin beta-4 rather than the fragment.
Pharmacokinetics
Published reviewEstimated from work on the parent protein. No human pharmacokinetic study of the fragment has been published; weekly dosing in community protocols is not derived from a measured half-life.
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 |
|---|---|---|---|---|---|---|
| Loading, commonly described | 2 mg – 5 mg | Twice weekly for the first four to six weeks | Subcutaneous | from 100 u | Community practice | Start this |
| Maintenance, commonly described | 2 mg – 2.5 mg | Once weekly or every other week | Subcutaneous | from 100 u | Community practice | Start this |
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.
Cycling
Community practice4 to 6 weeks at loading doses on, Reduced or paused thereafter off.
The loading-then-maintenance pattern is a community convention. No study has tested it, and it does not derive from any measured pharmacokinetic property.
Calculator
Work out what to draw
Pre-filled with a 5 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 2.5 mg of TB-500.
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
- Injection site reactionsCommunity practice
Commonly reported
- Fatigue or lethargy in the hours after a doseCommunity practice
Occasionally reported
- Head rush or transient lightheadednessCommunity practice
Occasionally reported
- Long-term effectsCommunity practice
Unknown
No human safety study has been published.
When to stop
- Signs of infection at an injection site: spreading redness, warmth, swelling, pus, or fever.
- Any allergic response: rash, hives, facial or lip swelling, or difficulty breathing. Seek urgent care.
- Any new lump, growth or unexplained change you would ordinarily have investigated.
- Before planned surgery, and tell your surgical team.
Interactions and situations that need care
- Active or previous cancerUse caution
Thymosin beta-4 promotes cell migration and new blood vessel formation, which are processes tumour growth and spread also rely on. This has not been studied in people with cancer in either direction, and the uncertainty is the reason for caution.
- Pregnancy and breastfeedingAvoid
No reproductive or developmental safety data exists.
- Competing in a tested sportAvoid
Prohibited at all times by the World Anti-Doping Agency and detectable in testing.
- Children and adolescentsAvoid
No safety data in any age group.
SportProhibited by the World Anti-Doping Agency under S2: Peptide Hormones, Growth Factors and Related Substances, at all times. Detectable in anti-doping testing.
What to expect
HonestlyThere is no human efficacy data for this compound, so there is no evidence-based timeline to give. Any site publishing a week-by-week schedule of expected effects has invented it.
- There is no human efficacy data for the fragment, so no timeline of expected effects can be given honestly.
- Much of what is written about TB-500 online cites research on full-length thymosin beta-4. That research is real; it is about a different molecule.
- Weekly dosing conventions are inherited from community practice, not from a measured half-life in humans.
- As with any injury treatment taken during recovery, separating an effect from ordinary healing is not possible without a control.
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 lyophilised powder is stable at −20 °C or colder for considerably longer than refrigeration allows.
With other peptides
- BPC-157synergistic
Frequently combined in community protocols on the reasoning that they act through different repair pathways. No controlled study has tested the combination.
- Thymosin Beta-4caution
This compound is a fragment of thymosin beta-4. Running both is taking the same activity twice. The human trials people cite for TB-500 were run on the full protein, not on this.
In use
Stacks with TB-500 in them
Documented combinations, with full schedules.
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. More on assessing quality and COAs.
White, fluffy cake
Correctly lyophilised powder forms a light cake across the vial bottom.
Clear once mixed
The solution should be completely clear after gentle swirling.
Collapsed or melted cake
Indicates heat exposure in transit. Refrigerating it afterwards does not reverse the damage.
Cloudiness or particles after mixing
Suggests degraded or contaminated material.
Questions
- Is TB-500 the same as thymosin beta-4?
- No. Thymosin beta-4 is a full 43-amino-acid protein that occurs naturally in the body. TB-500 is a shorter synthetic fragment of it. Research on the full protein is often cited as if it applied to the fragment, and that inference has not been established.
- Why are TB-500 doses so much larger than BPC-157 doses?
- Community protocols for TB-500 are usually discussed in milligrams per week rather than micrograms per day, so a typical dose is several thousand micrograms. Entering the two in the same units by mistake is an easy error. That is why the calculator always shows the unit alongside the number and refuses a dose larger than the vial.
References
Thymosin β4: actin-sequestering protein moonlights to repair injured tissues
Trends in Molecular Medicine, 2005 · Review
Animal models and in vitro
Describes actin sequestration as the protein's primary activity and reviews reported roles in cell migration, angiogenesis and wound repair.
10.1016/j.molmed.2005.07.002
Commonly reported community protocols
Bioalmanac editorial summary of public community sources, 2026 · Not a study
Summarises the loading and maintenance patterns most consistently described in public discussion. Carries no evidential weight about safety or effect.
TB-500 compared with
Related compounds
BPC-157
A synthetic 15-amino-acid peptide studied in animals for effects on tendon, ligament and gut tissue repair. No completed human trials.
Thymosin Beta-4
The full 43-amino-acid protein that TB-500 is a fragment of. It reached phase 2 trials in humans. TB-500 never has.
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 TB-500
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. TB-500 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 TB-500 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 12 Aug 2026