Thymosin Alpha-1 Dosing Guide: Protocols (2026)

Thymosin alpha-1 (Tα1) is a 28-amino acid peptide originally isolated from thymic tissue as the compound responsible for restoring immune function. Its synthetic form, thymalfasin (Zadaxin®), is approved in over 30 countries and has been studied in more than 11,000 human subjects across clinical trials.

One of the most clinically studied immune peptides: Thymosin alpha-1 has extensive human trial data for hepatitis, cancer immunotherapy, and sepsis. It is not FDA-approved in the US but has broad international approval. This is not medical advice.

Quick Reference: Dosing

Clinical standard: 1.6 mg subcutaneous twice weekly — the dose used across most clinical trials. Community acute protocol: 1.6 mg daily for 1–2 weeks during active infection, then transition to twice weekly.

For complementary immune peptides, see our LL-37 Dosing Guide and Thymulin Dosing Guide.

Loading vs Maintenance

Thymosin alpha-1 protocols vary based on the clinical context:

Acute immune support (Community):

• Week 1–2: 1.6 mg daily to rapidly upregulate immune function
• Week 3+: Transition to 1.6 mg twice weekly for maintenance

Chronic immune support (Clinical model):

• Throughout: 1.6 mg twice weekly, continuous for 6–12 months
• This mirrors hepatitis B trial protocols

Seasonal/preventive (Community):

• 4–8 week courses at 1.6 mg twice weekly during cold/flu season or travel
• Rest periods between courses

Timing Considerations

• Morning dosing: Preferred — aligns with natural immune circadian rhythms
• Consistent schedule: Twice-weekly injections on the same days (e.g., Monday/Thursday)
• Not meal-dependent: Can be taken with or without food
• Pre-travel: Some start courses 1–2 weeks before international travel

Routes of Administration

Subcutaneous Injection (Standard and Only Route)

All clinical data is based on subcutaneous administration:

• Injection sites: Upper arm, abdomen, or thigh — rotate between sites
• Volume: Typically 0.3–0.5 mL per injection
• Needle: 29–31 gauge, ½ inch insulin syringe
• Absorption: Rapid, with peak serum levels within 2 hours

Reconstitution Guide

Where These Numbers Come From: Clinical Context

Thymosin alpha-1 has one of the strongest clinical evidence bases of any peptide in the research community.

Immune Modulation Research

Thymosin alpha-1 has a pleiotropic mechanism affecting multiple immune cell subsets, including T-cells, NK cells, dendritic cells, and macrophages. A comprehensive review confirmed its role in restoring immune function across diverse clinical settings (Tuthill et al., 2016).

Hepatitis B Trials

Thymalfasin was extensively studied for chronic hepatitis B at 1.6 mg twice weekly for 6–12 months, showing improved virological response rates and enhanced vaccine responsiveness in immunocompromised patients.

Sepsis Clinical Data

A large Phase III trial (TESTS) evaluated thymosin alpha-1 at 1.6 mg twice daily for 5 days then twice weekly in sepsis patients, providing significant data on immune modulation in critical illness (Li et al., 2025).

An earlier meta-analysis of thymosin alpha-1 for sepsis showed trends toward reduced mortality from multiple organ failure, supporting its immune-supportive role in critical care (Li et al., 2015).

Comprehensive Safety Review

A narrative review covering over 11,000 human subjects across 30+ trials confirmed thymosin alpha-1's excellent safety profile with no dose-limiting toxicities identified (Dinetz et al., 2024).

Broad Literature Review

Dominari et al. (2020) provided a comprehensive review of thymosin alpha-1's immunomodulatory properties, clinical applications in viral infections, cancer, and vaccine enhancement, confirming its status as one of the most studied immune peptides (Dominari et al., 2020).

Mechanism of Action

Thymosin alpha-1 works through multiple immune pathways simultaneously:

Dendritic cell maturation — Tα1 promotes maturation and differentiation of dendritic cells, the professional antigen-presenting cells that bridge innate and adaptive immunity. This enhances the immune system's ability to recognize and respond to pathogens and tumors (Tuthill et al., 2016).

T-cell activation and differentiation — Enhances CD4+ and CD8+ T-cell function, promotes Th1-type immune responses, and increases T-cell receptor diversity. Particularly beneficial in immunocompromised states.

NK cell enhancement — Increases natural killer cell activity and cytotoxicity, strengthening innate immune surveillance against viral-infected and transformed cells.

Toll-like receptor signaling — Tα1 signals through TLR-9 and TLR-2 pathways, activating innate immune recognition cascades. This makes it an effective immune adjuvant when combined with vaccines.

Immune balance (not just stimulation) — Critically, Tα1 modulates rather than simply stimulates the immune system. It can enhance under-active immune responses while also supporting regulatory T-cell function to prevent excessive inflammation (Dominari et al., 2020).

Vaccine adjuvant activity — Enhances antibody responses to vaccines, particularly in immunocompromised individuals such as elderly, HIV-positive, or dialysis patients who typically show poor vaccine responses.

Side Effects & Safety

Thymosin alpha-1 has an exceptional safety record across thousands of clinical trial subjects:

Side Effects (From Clinical Trials)

• Injection site reactions — Mild erythema, minor discomfort (most common, transient)
• No dose-limiting toxicities identified in clinical trials
• No significant organ toxicity reported
• No immune overstimulation — Despite immune-enhancing properties, autoimmune flares are not commonly reported

Safety Profile Highlights

• >11,000 subjects across 30+ clinical trials
• Approved in 30+ countries — decades of post-marketing surveillance
• No significant drug interactions identified
• Safe in immunocompromised — Extensively used in HIV, hepatitis, and cancer patients
• Safe in elderly — Used for vaccine enhancement in aged populations

Theoretical Considerations

• Autoimmune conditions — While Tα1 modulates rather than simply stimulates immunity, caution is warranted in active autoimmune disease
• Organ transplant — Immune enhancement could theoretically affect transplant tolerance; use only under medical supervision
• Long-term continuous use — Most trial data covers 6–12 months; decades of continuous use unstudied

Stacking Thymosin Alpha-1

Thymosin alpha-1's immune-modulating properties make it complementary to several peptides:

Thymosin Alpha-1 + LL-37 (Immune Defense Stack)

The premier immune support combination:

• Thymosin alpha-1 → adaptive immune modulation (T-cells, NK cells, dendritic cells)
• LL-37 → innate immune defense (direct antimicrobial, cathelicidin pathway)

Thymosin Alpha-1 + BPC-157

Immune support with tissue healing:

• Thymosin alpha-1 → immune modulation and pathogen defense
• BPC-157 → tissue repair, gut healing, systemic anti-inflammatory

Thymosin Alpha-1 + Thymulin

Dual thymic peptide approach:

• Thymosin alpha-1 → broad immune modulation via dendritic cells and T-cells
• Thymulin → thymic hormone, T-cell maturation, zinc-dependent pathway

Thymosin Alpha-1 + GHK-Cu

Immune + anti-aging combination:

• Thymosin alpha-1 → immune surveillance and defense
• GHK-Cu → tissue repair, antioxidant support, gene expression modulation

Stacking Considerations

• Different injection sites — Rotate when using multiple injectable peptides
• Start individually — Assess thymosin alpha-1 response for 2+ weeks before adding compounds
• Acute vs. maintenance — Increase thymosin alpha-1 frequency during acute immune challenges while keeping stack peptides at maintenance doses
• Monitor immune markers — CBC with differential and inflammatory markers if available

Frequently Asked Questions

What is the standard thymosin alpha-1 dose?

1.6 mg subcutaneous twice weekly — the dose validated across most clinical trials. Community acute protocols may use daily dosing for 1–2 weeks before transitioning to twice weekly.

How long should a thymosin alpha-1 cycle last?

Clinical trials ran 6–12 months for hepatitis. Community immune support protocols typically use 4–12 week courses, with some running ongoing twice-weekly maintenance.

Can thymosin alpha-1 be stacked with LL-37?

Yes — this is the premier immune defense stack. Tα1 handles adaptive immune modulation while LL-37 provides direct antimicrobial activity and innate immune support. They work through completely different mechanisms.

Is thymosin alpha-1 FDA-approved?

Not in the US. However, thymalfasin (Zadaxin®) is approved in 30+ countries for hepatitis B and immune support, with extensive clinical data across 11,000+ trial subjects.

Does thymosin alpha-1 have side effects?

An exceptional safety profile. Mild injection site discomfort is the most common side effect. No dose-limiting toxicities, organ damage, or immune overstimulation across large clinical trials.

How do I reconstitute thymosin alpha-1?

Add 1 mL bacteriostatic water to a 5 mg vial (5 mg/mL). 1.6 mg = approximately 32 units on an insulin syringe. Refrigerate after reconstitution, use within 28 days.

Related Guides

• LL-37 Dosing Guide — Antimicrobial peptide for immune stacking
• LL-37 Benefits — Detailed LL-37 research and mechanisms
• Thymulin Dosing Guide — Another thymic peptide for immune support
• BPC-157 Dosing Guide — Healing peptide with immune-supportive properties
• Peptide Stacking Guide — Principles for combining immune peptides

References

For educational and research purposes only. This is not medical advice. Thymosin alpha-1 (thymalfasin) is approved in 30+ countries but not FDA-approved in the US. Consult a healthcare provider for immune-related concerns.