WHAT STUDIES TESTED · THYMOSIN BETA-4
What TB-500 may change, and what thymosin beta-4 studies can't prove
The wound and heart claims sound strong. Most evidence came from lab animals treated with the intact protein. The short chain's effect in your body is still unknown.
What the first studies measured before the health claims
Rat studies measured skin repair. Mouse studies measured heart and stroke damage [7][6][8]. Those tests used thymosin beta-4, not TB-500.
TB-500 is a lab-made chain with seven linked parts. It copies the seven amino acids at positions 17 through 23 of thymosin beta-4 [1]. A chemical name and lab weight don't show that an injury heals.
The full thymosin beta-4 parent protein has forty-three linked parts. It weighs about 4963 daltons; chemists use that unit for molecules too small to see [5]. TB-500 keeps only the short part that holds actin. Cells use actin to hold their shape and to move.
A lab test showed full thymosin beta-4 holding actin in a 1:1 match [1]. That means one part of each joined together. It doesn't show that the full protein heals you. A human study hasn't settled the short chain's effect on an injury [10].
Keep the two substances apart when you weigh a claim. The page on how it works explains how the short chain holds actin. The rest of thymosin beta-4 may do more. The seven-part chain hasn't been shown to match it.
What the TB-500 peptide is made from
The TB-500 peptide isn't a mix. Seven protein building blocks, called amino acids, form the chain. It weighs about 889 daltons; chemists use that unit for molecules too small to see [1]. The same chain has also had a name used in animal sales.
Researchers study the short part because it holds actin [1]. Cells rely on actin for shape and movement. Older lab work found that thymosin beta-4 stores spare actin until a cell needs it [2].
The full thymosin beta-4 protein has other parts that TB-500 leaves out. Those missing parts may have other effects [5]. A result for the full protein doesn't pass to the short chain. Marketing pages often skip that rather large detail.
What changed in the lab, in animals, and in people
An X-ray gave an atom-sized view at 2 angstroms. It showed thymosin beta-4, actin, and 1 part of another protein. Thymosin beta-4 held actin in a 1:1 match [1]. That shows a grip inside a cell, not healing in your knee.
A rat study then tested full thymosin beta-4 on deep wounds. New skin covered 42% more after four days and 61% after seven days [7]. A picogram is a trillionth of a gram; in the dish, 10 picograms made skin cells move faster. Moving cells may help cover a wound, but a dish can't show healing in your body.
A mouse study used full thymosin beta-4 after a blocked heart artery. The animals' hearts worked better [6]. Researchers did not test the shorter chain.
A Phase 1 study, the first step in human testing, put full thymosin beta-4 into a vein. It included 40 healthy adults and tried 42, 140, 420, or 1260 mg [10]. The adults handled the tested amounts well. That finding applies to the whole protein, not TB-500.
What human studies still haven't answered
People have not had the short chain tested in a finished comparison study [10]. Human work used only full thymosin beta-4. That work included one Phase 1 vein study.
Dry-eye studies used drops called RGN-259 made from full thymosin beta-4 [10]. Those drops did not contain the short chain. Neither study answers whether the short chain helps your injury.
There also isn't a sound human TB-500 half-life, meaning we don't know how long the seven-part chain stays in your blood. Horse tests can spot the substance, but they weren't made to guide human care [1].
A 2026 Sports Medicine review checked both approved and unapproved peptides. It named TB-500 and thymosin beta-4. The review found far more animal work than sound human safety work [11]. It also said severe harm could occur.
TB-500 isn't an FDA-approved drug, and FDA once marked it as a concern for pharmacy-made drugs. The requester later pulled the review request, but that did not approve the drug or clearly let pharmacies make it. If you're asking is TB-500 FDA approved, the answer is no; the TB-500 legal status and pharmacy rules page explains the withdrawal.
What people say happened, and what studies can prove
The TB-500 effects and safety page keeps two things apart. People describe what they felt. Studies record what researchers measured. A personal account can't prove the substance caused a change.