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Peptides/Longevity

Thymosin alpha-1

Also sold as Zadaxin, Ta1

An immune-modulating peptide approved in dozens of countries but not the US or UK. Real hospital use, oversold as a wellness product.

Research onlyMixed human evidence
Photo by The African Union Mission in Somalia · CC0 1.0 · source

At a glance

What people use it for

  • Supporting immune function during illness
  • Used clinically for hepatitis B and C in some countries
  • Marketed for chronic fatigue and frequent infections

How it is taken

An injection under the skin. Prescribed in countries where it is licensed; sold as a research chemical elsewhere.

Evidence

Mixed human evidence

Good to know

  • Not approved in the US or UK, so supply there is unregulated
  • Injection site reactions and occasional flu-like symptoms
  • Anyone with an autoimmune condition should be cautious about immune stimulation
  • Wellness marketing goes far beyond the licensed uses

Thymosin alpha-1 is a fragment of a protein produced by the thymus, the gland that trains immune cells. It sits in an unusual position: a licensed medicine in more than thirty countries, and a research chemical in the US and UK.

What people take it for

In countries where it is licensed, it is used clinically alongside treatment for hepatitis B and C, and as an immune support in sepsis and some cancers. It was studied during the COVID-19 pandemic.

The wellness market sells it for something rather different: frequent colds, chronic fatigue, and general immune support in otherwise healthy people.

What the evidence shows

More than most compounds in this section. There are randomised trials in hepatitis and in sepsis, and reviews have generally found it well tolerated with modest benefits in specific clinical settings. Thirty-plus national regulators have assessed and approved it for something.

The evidence for everyday wellness use is thinner. Studies in unwell hospital patients say very little about whether a healthy adult gets fewer colds, and no good trial has asked that question.

What to know before

Immune stimulation is not universally desirable. For anyone with an autoimmune condition, encouraging the immune system to do more is a poor idea, and that is a conversation for a doctor rather than a supplier.

Where it is not licensed, everything sold under this name is unregulated, whatever its status elsewhere.

Last reviewed .