TB-500
Also called Thymosin beta-4 fragment; Ac-LKKTETQ
Usually refers to a short, modified fragment of thymosin beta-4, not the full-length peptide used in most of the studies cited to support it. Human evidence does not establish it as a treatment for tendon or soft-tissue injuries.
Overview
What it is
Full-length thymosin beta-4 has 43 amino acids. The TB-500 fragment identified in testing has seven (LKKTETQ, positions 17-23) with an acetyl group. FDA's 2026 review found products sold as "TB-500" vary in salts, derivatives and even active molecule.
How it works
Full-length thymosin beta-4 helps cells move and promotes new blood vessels. In a 1999 rat study it sped skin wound closure and increased collagen. A 2024 lab study suggests metabolites of TB-500 may matter, but did not show human benefit.
What the research shows
A phase 2 trial of full-length thymosin beta-4 eye drops for dry eye improved some secondary measures but not its primary endpoints. A phase 1 study of recombinant thymosin beta-4 in healthy volunteers looked at short-term safety only. No adequate human studies of the TB-500 fragment exist.
Studied for
- Skin wound healingfull-length, rats
- Dry eyefull-length eye drops, phase 2, mixed
- Wound-healing activity of metaboliteslab
Safety and regulatory status
Safety and side effects
FDA found no clinical studies adequate to characterize use in people and cited concerns about immune responses, aggregation and impurities. Missing safety data are not evidence of safety.
Regulatory status
Not an ingredient in any FDA-approved drug; on FDA's list of compounding substances with safety risks. Prohibited at all times by WADA (S2.3).
Mixing and dosing reference
Reference information only. Read before using this section.
TB-500 (5 mg Vial) Dosage Protocol
- Vial
- 5 mg TB-500
- Add diluent
- 3 mL
- Concentration
- 1.67 mg/mL
- 1 unit (U-100)
- 16.67 mcg in 0.01 mL
- Route
- Subcutaneous
- How often
- Once per day (subcutaneous).
- Typical range
- 500–1000 mcg once daily (gradual titration recommended).
- Cycle length
- 8–12 weeks; optional extension to 16 weeks based on research protocol.
Standard / Gradual Approach
| Phase | Daily Dose (mcg) | Units (per injection) (mL) |
|---|---|---|
| Weeks 1–2 | 500 mcg | 30 units (0.30 mL) |
| Weeks 3–4 | 600 mcg | 36 units (0.36 mL) |
| Weeks 5–8 | 750 mcg | 45 units (0.45 mL) |
| Weeks 9–12 | 1000 mcg | 60 units (0.60 mL) |
How to mix
- Draw 3.0 mL bacteriostatic water with a sterile syringe.
- Inject slowly down the vial wall; avoid foaming.
- Gently swirl/roll until dissolved (do not shake).
- Label with date and concentration; refrigerate at 2–8 °C (35.6–46.4 °F), protected from light.
Dosing details
- Start: 500 mcg daily; increase by ~100–150 mcg every 2 weeks as tolerated.
- Target: 750–1000 mcg daily by Weeks 5–12.
- Frequency: Once per day (subcutaneous).
- Cycle Length: 8–12 weeks; optional extension to 16 weeks based on research protocol.
- Timing: Any consistent time daily; rotate injection sites systematically.
Administration technique
- The primary table uses U-100 syringe markings as volume measurements. One unit equals 0.01 mL; it is not an international unit of TB-500 activity.
- Use a new sterile syringe for each recorded administration and dispose of it in an approved sharps container.
- Clean the vial stopper and skin, then allow both surfaces to dry before the procedure.
- Measure the exact U-100 marking at eye level and check that the matching mL value agrees with the table.
- Use the institution’s approved subcutaneous-injection procedure for site selection, needle angle, administration, and site rotation.
- Document date, time, vial lot, concentration, volume, syringe units, and observations in the research record.
Protocol source: PeptideDosages.com
Common questions
Is TB-500 the same as thymosin beta-4?
Usually not. It is typically a seven-amino-acid fragment.
Is the BPC-157 + TB-500 "Wolverine stack" better?
No controlled study shows an added benefit.
Is it allowed in sport?
No. It is banned in and out of competition.
Found in these blends
Related in Performance and Recovery
Sources and further reading (6)
- Ho ENM, et al. Doping control analysis of TB-500, 2012.
- FDA. TB-500-related bulk drug substances, July 2026 advisory briefing.
- Malinda KM, et al. Thymosin beta4 accelerates wound healing, 1999.
- Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution in dry eye: phase II, 2015.
- WADA. 2026 Prohibited List, S2.3.
- Source summary: PeptideDosages.com research overview (rewritten for NVO).
Laboratory research material: TB-500 Research Use Only