Also called Thymosin beta-4 fragment, Thymosin β4 (Tβ4), Ac-LKKTEKK
A lab copy of part of a repair protein, popular for injuries but barely tested.
Thymosin beta-4 is a protein your body makes in almost every cell, and it helps cells move to where a wound is. TB-500 is a lab-made version, usually a short active piece of it. What's sold as TB-500 can be either the short piece or the full protein, and the label doesn't always say which.
It helps cells crawl and change shape, so in animals repair cells can reach injured tissue. Animal studies also show it supports new blood vessels and calms swelling. None of this has been proven in people for injury repair.
Mostly animal studies
Most of the evidence comes from animals and cells. The full protein (not the short TB-500 piece) has had a little testing in people: an IV safety study in 40 healthy volunteers found it well tolerated, and eye-drop versions for dry eye had mixed results. There are no human trials of TB-500 shots for sports injuries, so the doses people use come from community practice, not studies.
Why: People load up on it for a fresh injury and spread doses across the week. This is a community habit, not something tested in a trial.
Why: After loading, people drop to a lower, less frequent dose. There's no human data on which dose or schedule is best.
Start at the low end, and change one thing at a time. If you take medication or have a health condition, check with a doctor first.
Set up for a 5 mg vial. Change any number to match yours. New to this? Read how to mix a vial and mg vs mL vs units first.
Pick your dose and how long you'll run it. We'll count what you need.
Get help right away for swelling of the face or throat, trouble breathing, chest pain, or a spreading, hot, red injection site.
Powder: fridge or freezer, out of light. Once mixed with bacteriostatic water: fridge, use within about 4 weeks.
FDA: Not approved. FDA removed thymosin beta-4 fragment from its Category 2 compounding risk list in April 2026. On July 23, 2026 the FDA's Pharmacy Compounding Advisory Committee voted to recommend adding it to the 503A bulks list. That is advice only; FDA has not made it final.
Sport (WADA): Prohibited at all times (S2, growth factors). WADA names thymosin-β4 and its derivatives, such as TB-500.
Not exactly. TB-500 usually means a short lab-made piece of thymosin beta-4, though some products are the full protein. The human safety data is for the full protein, not the short piece.
It's thought to travel through the body, so most people inject it under the skin of the belly. There's no human evidence that the spot matters.
Yes. Sports drug-testing labs check for it, and it's banned at all times.
Last checked 2026-10