Immune & gut
Thymosin alpha-1, simplified.
Also called Tα1, Zadaxin
Human studiesAn immune-boosting peptide from the thymus gland, approved in dozens of countries but not the US.
- Size
- 28 amino acids
- How it is taken
- Injection
- Status
- Approved abroad, not in the US
What is it?
The thymus is where some immune cells learn their job. Thymosin alpha-1 helps those T cells mature and respond.
What studies show
- In peopleIt is approved in many countries to support treatment of hepatitis B and C.
- In peopleIt has been studied alongside vaccines and in serious infections, with mixed results.
What we don’t know yet
- Whether it helps healthy people with "immune support".
Side effects and cautions
- Generally well tolerated in trials.
Is it legal?
Not FDA-approved. Included in the 2026 HHS compounding plan.
Common questions
What is Thymosin alpha-1?
An immune-boosting peptide from the thymus gland, approved in dozens of countries but not the US. The thymus is where some immune cells learn their job. Thymosin alpha-1 helps those T cells mature and respond.
What does the research say about Thymosin alpha-1?
It is approved in many countries to support treatment of hepatitis B and C. It has been studied alongside vaccines and in serious infections, with mixed results.
Is Thymosin alpha-1 FDA approved?
Not FDA-approved. Included in the 2026 HHS compounding plan.
What are the side effects of Thymosin alpha-1?
Generally well tolerated in trials.
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This page explains published research in plain language. It is not medical advice, a diagnosis, or a recommendation to take anything, and it does not give dosing. Most peptides here are not FDA-approved, and products sold online vary widely in purity. Rules around peptides are changing, so check the current status and talk with a licensed clinician before starting anything. Last reviewed 2026-09-26.