Legal status · Record reviewed
Thymosin alpha-1 has no single legal status. It depends on the product and how it is supplied.
No FDA-approved thymosin alpha-1 product was identified in the United States as reviewed August 30, 2026.
Pharmacy mixing (compounding): FDA had placed it in Category 2 for possible safety risks, and the request was then withdrawn (FDA page dated April 22, 2026).
Sports: we found no ban in the rules we checked (checked August 30, 2026). That does not clear you to compete.
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Approved outside the U.S. only
A regulator in another country allowed a product. The record found no FDA-approved product in the United States.
What the record says: No FDA-approved thymosin alpha-1 product was identified in the United States as reviewed August 30, 2026
Nomination withdrawn
FDA had placed it in Category 2 for possible safety risks. The person who asked FDA to allow it in compounding then withdrew the request. FDA still lists its safety concerns and has not made a final decision. A withdrawn request is neither a ban nor an approval.
Source: FDA's page of bulk drug substances that may present significant safety risks. FDA marks it current as of . We checked it on .
No prohibition identified
Thymosin alpha-1 is not named in the reviewed 2026 WADA list. Thymosin beta-4 and TB-500 are different substances and are named. This is not personal clearance. Athletes must check the current list and their sport rules.
Checked . Read the rule we checked. Check the current World Anti-Doping Agency list and your sport's rules before you compete.
Other names in this record: TA1, Ta1, Tα1, Thymalfasin.
What it is, what studies in people show, and what is still unknown.
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