IMMUNE · PEPTIDE
What is Thymosin Alpha-1?
Medically reviewed by the G1 Peptides clinical team · Updated October 1, 2026
THE SHORT ANSWER
Thymosin alpha-1 is a peptide of 28 amino acids produced naturally by the thymus gland. It helps regulate the immune system, particularly T cells, and a synthetic version is used in many countries as an immune therapy.
Thymosin Alpha-1 at a glance
- Type
- Peptide
- Also known as
- Thymalfasin, Zadaxin, Tα1
- Mechanism
- Thymic peptide; T-cell and dendritic-cell modulation
- Status
- Approved outside US
- Half-life
- ~2 hours
- Route
- Subcutaneous
- Dosing range in the literature
- 1.5–3.2 mg per dose
- Onset
- 2–4 weeks
- Storage
- Refrigerated (2–8 °C); use within the pharmacy beyond-use date
How Thymosin Alpha-1 works
It promotes the maturation of T cells and activates dendritic cells, which coordinate immune responses. It tends to restore balance: strengthening weak responses without broadly overstimulating the immune system.
What Thymosin Alpha-1 is studied for
- Immune modulation
- Vaccine response
- Infection recovery
It has been studied in hepatitis B and C, as a vaccine booster in people with weak immune responses, and in severe infections, with mixed but generally favourable results.
Being studied for something is not proof that it works. Results in individuals vary.
Thymosin Alpha-1 dosing
Published protocols describe 1.5–3.2 mg per dose, twice weekly, given subcutaneous. Onset is typically reported at 2–4 weeks.
These figures are context from the literature, not instructions. A licensed provider sets the dose and schedule for each patient.
Thymosin Alpha-1 side effects and risks
- Injection-site reactions
- Mild fatigue
Tell your provider about every medication and condition before starting, and report anything unexpected. See peptide side effects and safety and who should not use peptides.
Is Thymosin Alpha-1 FDA approved?
Approved in more than 30 countries as thymalfasin. Not FDA-approved.
Approval and trial status change. This page was last reviewed on October 1, 2026.
Thymosin Alpha-1 at G1 Peptides
G1 Peptides supplies Thymosin Alpha-1 as vials (10 mg, 20 mg). Prescription products ship only after a licensed provider has reviewed the order.
Thymosin Alpha-1 questions
- What is Thymosin Alpha-1?
- Thymosin alpha-1 is a peptide of 28 amino acids produced naturally by the thymus gland. It helps regulate the immune system, particularly T cells, and a synthetic version is used in many countries as an immune therapy.
- What is Thymosin Alpha-1 used for?
- Thymosin Alpha-1 is studied for immune modulation, vaccine response, and infection recovery. It has been studied in hepatitis B and C, as a vaccine booster in people with weak immune responses, and in severe infections, with mixed but generally favourable results.
- How does Thymosin Alpha-1 work?
- It promotes the maturation of T cells and activates dendritic cells, which coordinate immune responses. It tends to restore balance: strengthening weak responses without broadly overstimulating the immune system.
- Is Thymosin Alpha-1 FDA approved?
- Approved in more than 30 countries as thymalfasin. Not FDA-approved.
- What is the typical Thymosin Alpha-1 dosage?
- Published protocols describe 1.5–3.2 mg per dose, given subcutaneous. This is context from the literature, not a recommendation: a licensed provider sets the dose.
- What are the side effects of Thymosin Alpha-1?
- Risks noted for Thymosin Alpha-1 include injection-site reactions and mild fatigue. Tell your provider about your medications and conditions before starting.
- What is the half-life of Thymosin Alpha-1?
- The reported half-life is ~2 hours. Onset is typically reported at 2–4 weeks.
- How should Thymosin Alpha-1 be stored?
- Refrigerated (2–8 °C); use within the pharmacy beyond-use date.
For educational purposes only, and not medical advice. These statements have not been evaluated by the FDA. Nothing on this page is intended to diagnose, treat, cure, or prevent any disease. Use any compound only under the guidance of a licensed provider.