Compounds / TB-500
TB-500
Thymosin beta-4 fragment 17-23, Ac-LKKTETQ
TB-500 is a lab-made peptide of 7 amino acids. It copies one short stretch (amino acids 17 to 23) of thymosin beta-4, a natural protein that is 43 amino acids long, with an acetyl group added at one end1.
It isn't FDA-approved, and FDA found no studies in which it was given to people1. The World Anti-Doping Agency (WADA) bans it in sport at all times3.
- Status
- Not approved anywhere
- Human evidence
- None published
- Type
- 7-amino-acid piece of thymosin beta-4
- Sport
- Banned by WADA at all times
What is TB-500?
TB-500 is a lab-made peptide of 7 amino acids (LKKTETQ) with an acetyl group added at one end. Those 7 amino acids are positions 17 to 23 of thymosin beta-4, a natural protein 43 amino acids long that's found in blood, saliva, tears and wound fluid1.
Many websites call TB-500 “synthetic thymosin beta-4”, but FDA says they aren't the same substance1. It appears to have been first made in 2003, and a veterinary version appeared in 2011, marketed to boost performance in racehorses and greyhounds1. Today it's sold online for injury recovery, muscle, hair growth and much else, often as powder labeled for research use only1.
Is TB-500 legal? Status by country
TB-500 isn't an approved medicine in the US, UK, EU, Canada or Australia1. Australia goes further and makes it a prescription-only medicine that's illegal to possess without authority11.
| Where | What the rules say |
|---|---|
| United States | Not FDA-approved and not on the 503A Bulks List. FDA's reviewers recommended against adding it for wound healing1. Its advisers discussed it on July 23, 2026, and FDA had posted no decision when we checked on November 9, 202610 |
| United Kingdom and EU | No approved product in the UK or several other European countries, and none authorized by the European Medicines Agency1 |
| Australia | Schedule 4 (prescription only). Appendix D, clause 5 makes possession without a prescription or other authority illegal. Thymosin beta-4 is listed the same way11 |
| Canada | No approved product1, and none in Health Canada's Drug Product Database14. Health Canada lists TB-500 among seized unauthorized injectable peptides12 |
| Sport (WADA) | Banned at all times under S2.3, “thymosin-ß4 and its derivatives e.g. TB-500”3 |
Health Canada says a “research use only” label doesn't make a peptide legal12. The research-use label guide explains what that wording does and doesn't mean.
What have TB-500 studies actually tested?
Very little. FDA found no studies in people, no animal studies of TB-500 for wound healing, and no animal toxicity studies1. Since FDA's review, one small rat study has been published4.
| Study | Tested in | What it found |
|---|---|---|
| Skin wounds, Philp 2003 | Aged mice | The same 7 amino acids without the acetyl group, put on wounds, sped up skin closure. That isn't TB-500 itself1 |
| Scratch wounds, Rahaman 2024 | Lab cells | TB-500 didn't help cultured connective tissue cells close a scratch. One of its breakdown products had a small effect1 |
| Doping test study, Ho 2012 | Horses | Blood levels peaked 1 to 2 hours after an injection and were too low to measure by 6 to 10 hours1 |
| Achilles tendon repair, Biçer 2026 | 32 rats | Stronger tendons and better tissue scores at 4 weeks than untreated rats. Adding BPC-157 gave no extra benefit4 |
| Any use | Humans | None found. FDA found no study in which TB-500 was given to people1 |
The acetyl group matters. FDA notes it changes how a peptide behaves, so results from the plain 7-amino-acid sequence can't be carried over to TB-5001.
Do thymosin beta-4 trials apply to TB-500?
No. The human trials you see quoted for TB-500 tested full thymosin beta-4, a different and much larger molecule. A 2026 review notes there is no shown biological or clinical equivalence between the two5.
| Trial | People | What it found |
|---|---|---|
| IV infusion, Ruff 2010 | 40 healthy volunteers, 14 days | Well tolerated, with no serious side effects6 |
| Gel on venous leg ulcers, Guarnera 2010 | 73 people | Safety similar to placebo. Hints that one strength may speed healing7 |
| Eye drops for dry eye, Sosne 2015 | 72 people | Missed both main goals, though some other measures improved. No side effects8 |
| Eye drops for severe dry eye, Sosne 2015 | 9 people | Less discomfort and eye surface damage than the plain drops9 |
None of these trials injected thymosin beta-4 under the skin for injuries, which is how TB-500 is usually sold.
Is TB-500 safe? What isn't known
Nobody knows. FDA found no human exposure data for TB-500 by any route, so its risks in people are unknown1. FDA lists it among compounding substances that may carry a risk of immune reactions and impurities2.
- No toxicity testing. FDA found no animal studies of TB-500's general toxicity, effects on pregnancy and fertility, or cancer risk1.
- Immune reactions and clumping. Injected peptides can trigger the immune system, and peptides can clump together. Reactions can range from none to severe1.
- Side effect reports. FDA's drug database had no TB-500 reports up to March 2025. Its food and supplement database had 2 reports about blended TB-500 and BPC-157, with no safety details1.
- Blends. A woman who injected a BPC-157 and TB-500 product developed darkening of the skin and gums, which came back when she used it again. With two peptides in the vial, FDA couldn't tell which caused it13.
How do you work out TB-500 units on a syringe?
Divide the TB-500 in the vial by the water you add, then work out how much each 0.01 mL unit on a U-100 insulin syringe holds. As an example of the math only, a 5 mg vial with 2 mL of bacteriostatic water is 2.5 mg/mL, so each unit holds 25 mcg and 500 mcg is 20 units (0.2 mL). That's not a dose from any study. No human dose of TB-500 has been tested.
TB-500 is often sold mixed with BPC-157 in one vial. Every unit of a blend holds some of each peptide, so the blend vial calculator is the one to use for those.
How does TB-500 compare with BPC-157?
BPC-157 has far more research, though almost all of it is in rats, plus three tiny human studies. TB-500 has almost none. The BPC-157 vs TB-500 comparison puts the two side by side.
No human half-life has been published for TB-500. The peptide half-life chart lists what is known for it and other peptides.
TB-500 fact sheet
- What it is
- A synthetic, N-acetylated 7-amino-acid fragment (amino acids 17 to 23, LKKTETQ) of thymosin beta-4. Not the same substance as thymosin beta-41
- Status (US)
- Not FDA-approved. FDA lists it as a compounding substance that was nominated, then withdrawn (page dated April 22, 2026). FDA's advisers reviewed it for wound healing on July 23, 2026; FDA's reviewers recommended against it, and FDA had posted no final decision by November 8, 20262
- Status (UK, CA, AU, EU)
- No approved TB-500 products in Canada, Australia, the UK or the EU, per FDA's review1
- Sport (WADA)
- Prohibited at all times, class S2.3: "thymosin-ß4 and its derivatives e.g. TB-500"3
- Evidence
- No human studies found by FDA, and no animal studies of TB-500 for wound healing. Since then, one small rat tendon study (2026) has been published1
- Doses used in studies
- Rats: 60 mcg/kg a day, injected into the belly, for 4 weeks after tendon repair. No human doses have been studied. Not a recommendation4
- Half-life
- Not established in humans. In horses given 10 mg, blood levels peaked at 1 to 2 hours and were too low to measure by 6 to 10 hours1
Mixing math for TB-500
For a vial you mix yourself. Example numbers only: change them to match your own vial and dose. This does the math; it doesn't recommend a dose.
The mg printed on the vial label.
Bacteriostatic (bac) water, in mL.
Check whether it says mcg or mg. They differ by 1,000 times.
It's printed on the packet: 0.3, 0.5 or 1 mL.
5 mg vial + 2 mL water → 500 mcg dose
Fill your syringe to
20units
The 20 line on a 1 mL syringe, which is 0.2 mL.
- Strength after mixing
- 2.5 mg/mL
- Each unit holds
- 25 mcg
- Doses in this vial
- 10
Show the math
- 5 mg × 1,000 = 5,000 mcg in the vial
- 5,000 mcg ÷ 2 mL = 2,500 mcg/mL
- 500 mcg ÷ 2,500 mcg/mL = 0.2 mL
- 0.2 mL × 100 units/mL = 20 units
Not what you expected? Check the numbers above, and confirm with your prescriber or pharmacist before you inject.
Questions
Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a natural protein of 43 amino acids, and TB-500 is a synthetic 7-amino-acid piece of it (amino acids 17 to 23) with an acetyl group added. FDA says the two are not the same substance, and a 2026 review notes there is no shown biological or clinical equivalence. So results from thymosin beta-4 trials don't apply to TB-500.
Has thymosin beta-4 been tested in people?
Yes, the full protein has. Trials include a 2010 phase 1 study of IV thymosin beta-4 (42 to 1,260 mg) in 40 healthy volunteers, a phase 2 trial of a topical gel in 73 people with venous leg ulcers, and phase 2 trials of 0.1% eye drops for dry eye. None of these tested TB-500.
Is TB-500 FDA approved?
No. TB-500 is not FDA-approved and isn't part of any approved medicine. On July 23, 2026, FDA's advisory committee reviewed it for possible pharmacy compounding (for wound healing), and FDA's own reviewers recommended against adding it. That advice isn't a final decision.
Where do TB-500 loading and maintenance schedules come from?
Not from clinical trials. FDA found no studies of any kind in which TB-500 was given to people, so there's no tested human dose, schedule or length of use. The loading and maintenance plans you see online aren't based on human data.
Is TB-500 banned in sport?
Yes. The WADA 2026 Prohibited List names TB-500 under S2.3 (thymosin-ß4 and its derivatives). Substances in S2 are prohibited at all times, in and out of competition.
How many units is 500 mcg of TB-500 in a 5 mg vial?
With 2 mL of bacteriostatic (bac) water, a 5 mg vial is 2.5 mg/mL, so 500 mcg is 20 units on a U-100 insulin syringe (0.2 mL). This is math only. The numbers are an example, not a dose from any study.
Sources
- 1FDA Briefing Document: TB-500-related bulk drug substances, Pharmacy Compounding Advisory Committee, July 23-24, 2026. sections I, II.A, II.B.4, II.C, II.D
- 2FDA: Certain bulk drug substances for use in compounding that may present significant safety risks. table of substances nominated but withdrawn; content current as of April 22, 2026
- 3World Anti-Doping Agency: 2026 Prohibited List. class S2.3, growth factors and growth factor modulators; in force from January 1, 2026
- 4Biçer O et al. Effects of BPC-157 and TB-500 on Achilles tendon healing in rats. Jt Dis Relat Surg. 2026;37(3):822-837
- 5Tham A et al. Investigational peptides in orthopaedic practice: BPC-157, thymosin beta-4, and TB-500. J Am Acad Orthop Surg. 2026
- 6Ruff D et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers. Ann N Y Acad Sci. 2010;1194:223-9
- 7Guarnera G et al. The effect of thymosin treatment of venous ulcers. Ann N Y Acad Sci. 2010;1194:207-12
- 8Sosne G, Ousler GW. Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, phase II trial. Clin Ophthalmol. 2015;9:877-84
- 9Sosne G, Dunn SP, Kim C. Thymosin β4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial. Cornea. 2015;34(5):491-6
- 10FDA: July 23-24, 2026 meeting of the Pharmacy Compounding Advisory Committee. agenda and materials; no minutes posted when checked on November 8, 2026
- 11Therapeutic Goods (Poisons Standard—October 2026) Instrument 2026, Federal Register of Legislation (Australia). in force from September 30, 2026; Schedule 4 entries for TB-500 and thymosin beta-4, and Appendix D, clause 5
- 12Health Canada: Think twice before injecting peptides bought online (public advisory RA-81874). published April 9, 2026
- 13FDA Briefing Document: BPC-157-related bulk drug substances, Pharmacy Compounding Advisory Committee, July 23-24, 2026. section II.D.2.b, FAERS case 26053573
- 14Health Canada Drug Product Database, active ingredient searches for TB-500 and thymosin. no products found for either search, November 9, 2026
This page explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.
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