Thymosin Alpha-1 Dosage Guide: Immune Protocol & Reconstitution

BHRC · LONGEVITY & WELLNESS · PEPTIDES

By Jamie Walston · Beverly Hills Rejuvenation Center · Reviewed by the BHRC Clinical Team

Thymosin alpha-1 occupies an unusual position among the peptides people ask us about. It is not a research chemical with a mechanism sketched from animal data — it is an approved medicine in more than thirty-five countries, with decades of clinical use and a real dosing record behind it. And it is still not approved in the United States, still not compoundable here, and still short of convincing effectiveness data in the conditions where it has been studied hardest. This guide covers the mechanism, the doses used in published studies, what the evidence actually found, the one serious safety signal, and how reconstitution and syringe arithmetic really work.

Thymosin alpha-1 peptide vial at Beverly Hills Rejuvenation Center — Thymosin alpha-1 is a 28–amino-acid thymic peptide. It is approved in more than 35 countries — but not in the United States.

Quick answer. Thymosin alpha-1 (Tα1, generic name thymalfasin) is a 28–amino-acid peptide made by the thymus that acts on toll-like receptors to modulate T-cell maturation and immune signalling. It is marketed as Zadaxin in more than 35 countries for hepatitis B and C — but it is not FDA-approved in the United States, and following an FDA advisory committee review in December 2024 it is not currently eligible for compounding here either. Doses in published clinical studies cluster around 1.6 mg subcutaneously, given twice weekly for hepatitis or daily for short courses in acute illness. The evidence is genuinely mixed: FDA reviewed it across twelve conditions and concluded there is a lack of evidence of effectiveness.

What this article is. An evidence review, not a protocol. The doses below are the ones used in published studies, reported so you can evaluate the research honestly — they are not a recommendation, and Tα1 is not something we can lawfully compound in the US today. If immune resilience is the underlying goal, a longevity consultation with baseline testing is the useful first step.

1 · What thymosin alpha-1 is

Your thymus is a small gland behind the sternum that trains T cells. It is at its largest in childhood and involutes steadily through adult life — which is one of the more concrete pieces of biology behind the observation that immune function changes with age.

In 1977, researchers isolated a peptide from calf thymus: an N-terminally acetylated chain of 28 amino acids. The synthetic version is called thymalfasin, and the brand name you will see internationally is Zadaxin.

Diagram of the four proposed mechanisms of thymosin alpha-1: TLR signalling, T-cell maturation, NK activation and cytokine modulation — It is a modulator rather than a stimulant — the described action is on how the immune system coordinates, not simply on how hard it runs.

That framing matters. “Immune booster” is the phrase used in marketing, and it is the wrong mental model. The described mechanism is modulation — nudging the coordination of an immune response — which is also why the interesting research questions have been in chronic viral infection and in sepsis rather than in preventing colds.

2 · Where it stands with the FDA — the exact position

This is the part most articles get wrong in one direction or the other, so here it is precisely.

Table of thymosin alpha-1 regulatory status showing no FDA approval and no compounding eligibility — Orphan drug designation is a regulatory incentive for developing a treatment for a rare disease. It is not an approval, and it does not mean a product may be sold.

Two clarifications worth making explicitly.

It was not part of the July 2026 peptide review. That advisory committee meeting covered seven substances — BPC-157, KPV, TB-500, MOTS-c, emideltide, semax and epitalon. Thymosin alpha-1 had its own separate review on 4 December 2024. If you see an article implying it was recommended in July 2026, that is a mix-up.

FDA’s recommendation was against listing it. The agency’s briefing document concluded that the physicochemical characterization, information on historical use, lack of evidence of effectiveness and safety information all weighed against adding Tα1 or its acetate to the 503A Bulks List. It now sits in FDA’s “nominated but withdrawn” table — which means it is not on the list of substances that may be compounded, and removal from a safety-concern category does not make a substance eligible.

Under federal law a bulk substance may be compounded only if it has a USP monograph, is a component of an approved drug, or appears on the 503A Bulks List. Thymosin alpha-1 currently meets none of the three.

3 · Doses used in published studies

Because Tα1 is an approved product in other countries, there is a real clinical dosing record for it — which distinguishes it from most peptides sold online. Here is what the studies used.

Table of thymosin alpha-1 doses used in published clinical studies for hepatitis B, COPD and sepsis — The recurring figure is 1.6 mg subcutaneously. Reported ranges across the literature run 0.8–6.4 mg for single doses and 1.6–16 mg across multi-dose courses.

On the COVID-era protocols. Thymosin alpha-1 was studied widely during the pandemic, and you will find confident dosing charts referencing that work. FDA’s own review found that COVID-era dosing was not consistently reported across the studies. There is no single “COVID protocol” dose to quote, and we are not going to invent one.

4 · What the evidence actually shows

This is where honest reporting departs sharply from the marketing.

Hepatitis B

This is the indication Tα1 is approved for internationally, so it is the strongest place to look. In monotherapy, the result is sobering: no difference in undetectable HBV DNA at six months post-treatment — 20% on Tα1 versus 21% on placebo. Combination regimens with interferon have shown more, but the single-agent monotherapy figure is the one that gets omitted from summaries.

COVID-19

Three of four meta-analyses found no decrease in mortality. That is the honest summary of a large and enthusiastic body of pandemic-era research.

FDA’s overall read

Statistics from FDA's 2024 review of thymosin alpha-1 showing limited evidence of effectiveness — A substance can be approved in dozens of countries and still not clear FDA’s evidentiary bar. Both facts are true here, and neither cancels the other.

The fair conclusion is not that Tα1 does nothing. It is that a peptide with a genuine mechanism, decades of international use and a reasonable safety record has nonetheless failed to produce convincing effectiveness data in the conditions where it has been studied hardest. That is a more interesting and more useful thing to know than either “miracle immune peptide” or “snake oil.”

5 · Safety — and the one serious signal

Tα1 is generally described as well tolerated. The most common adverse effect across studies is injection-site irritation, redness and discomfort. When used alongside interferon, the combination adds fever, fatigue, myalgia, nausea, vomiting and neutropenia — though those are largely interferon’s contributions.

The signal that deserves attention. FDA’s review flagged reports of fatal immune hemolytic anemia and engraftment failure in stem cell transplant recipients, and raised specific concern about use in patients undergoing deliberate immunosuppression. A peptide that modulates immune activation is precisely the wrong thing to introduce when immune suppression is the therapeutic goal.

Who should not use it

Transplant recipients, and anyone on immunosuppressive therapy
Anyone with an autoimmune condition, without specialist input — the reasoning follows from the mechanism rather than from a trial, and that distinction is worth stating
Anyone pregnant or breastfeeding
Children and adolescents
Anyone who cannot verify the sterility and identity of what they are injecting

6 · Reconstitution, and why sterility is the real risk

For any lyophilised peptide, the handling is not a footnote. FDA put it plainly in a 2026 warning letter to an online seller: injectable products are delivered directly into the body, sometimes into the bloodstream, and therefore bypass the body’s key defences against toxins and microorganisms.

Comparison table of bacteriostatic water versus sterile water for injection showing preservative content and appropriate use — At 9 mg/mL, a 0.2 mL subcutaneous injection delivers about 1.8 mg of benzyl alcohol — far below the adult reference exposure, which is why it is a non-issue at typical volumes in adults and a genuine issue in neonates.

Handling a lyophilised peptide

Add the diluent slowly down the inside wall of the vial, not directly onto the powder
Swirl or roll gently — never shake. Agitation creates air–liquid interfacial stress, which is the main mechanical driver of peptide aggregation
Let it dissolve on its own. Do not vortex and do not warm it
Refrigerate the reconstituted solution and protect it from light
Discard anything cloudy, discoloured or containing visible particles
Use the beyond-use date printed on the pharmacy label — not a rule of thumb from the internet

Aggregation is not an aesthetic concern. Aggregated peptide is the substrate for immunogenicity, and immunogenicity risk is exactly what FDA has cited repeatedly in its reviews of injectable peptides — compounded, it says, by unknown impurities in poorly characterised products.

Syringe arithmetic, done properly

A U-100 insulin syringe is marked in insulin units at 100 units per millilitre. 100 units = 1.0 mL, and 1 unit = 0.01 mL. When such a syringe is used for anything other than insulin, those units are volume markings only — they carry no potency meaning whatsoever.

Table showing how to convert a peptide dose in milligrams to units on a U-100 insulin syringe — This is arithmetic, not clinical advice — the doses shown are illustrative. Note that reconstituting the same vial with a different diluent volume changes every number in the row.

Every patient instruction should state the dose in milligrams or micrograms and the volume in units at a stated concentration. “Twenty units” on its own is not a dose — it is a volume, and it means something different from every vial.

7 · If immune resilience is the actual goal

Immune resilience is measurable. That is a better starting point than an unapproved injectable.

Nothing above says immune health is not worth working on. It says thymosin alpha-1 specifically is an interesting molecule that is neither available nor well-evidenced in the US right now.

The higher-yield starting point is measurement. Inflammatory markers, metabolic markers, vitamin D, thyroid function and hormone status all bear on how well an immune system works, and most people have something meaningful out of range. Advanced diagnostic testing establishes what is actually happening rather than what a protocol assumes, and longevity programs at BHRC are built downstream of that work rather than upstream of it.

Talk to a BHRC provider about peptide therapy
Physician-supervised peptide and longevity programs are available at all six BHRC studios. Consultations are free, include a review of your history and labs, and carry no obligation.
We will tell you plainly what is available, what is evidenced, and what is neither.

Frequently Asked Questions

Is thymosin alpha-1 FDA-approved?

No. It is not approved in the United States, Japan or Europe, with the exception of Italy. It is marketed as Zadaxin in more than 35 countries for hepatitis B and C. It holds US orphan drug designation for several conditions, but designation is a development incentive, not an approval.

Can a compounding pharmacy make it?

Not lawfully, as things stand. Thymosin alpha-1 was reviewed by FDA’s Pharmacy Compounding Advisory Committee on 4 December 2024, FDA recommended against adding it to the 503A Bulks List, and it now sits in FDA’s nominated-but-withdrawn table. It has no USP monograph and is not a component of an approved US drug, so none of the three statutory routes applies.

Was it part of the July 2026 peptide vote?

No — that is a common mix-up. The July 2026 advisory committee reviewed BPC-157, KPV, TB-500, MOTS-c, emideltide, semax and epitalon. Thymosin alpha-1 had its own separate review in December 2024.

What dose is used in the research?

The recurring figure is 1.6 mg subcutaneously. Hepatitis B studies used 1.6 mg twice weekly for 52 weeks; COPD studies used 1.6 mg over four weeks; sepsis protocols used 1.6 mg twice daily tapering to daily, or 10 mg daily. Reported ranges run 0.8–6.4 mg single-dose and 1.6–16 mg across multi-dose courses. These are study regimens, not a prescription.

Does it work?

The evidence is mixed and weaker than the marketing suggests. In hepatitis B monotherapy it produced no difference versus placebo in undetectable HBV DNA at six months — 20% versus 21%. Three of four COVID-19 meta-analyses found no mortality benefit. FDA reviewed it across twelve conditions and concluded there is a lack of evidence of effectiveness.

Is it safe?

It is generally described as well tolerated, with injection-site irritation the most common effect. The serious signal to know about is reports of fatal immune hemolytic anemia and engraftment failure in stem cell transplant recipients — FDA raised specific concern about use in patients undergoing deliberate immunosuppression.

Who should avoid it?

Transplant recipients and anyone on immunosuppressive therapy; anyone with an autoimmune condition without specialist input; anyone pregnant or breastfeeding; children and adolescents.

What is the difference between bacteriostatic and sterile water?

Bacteriostatic water contains benzyl alcohol 0.9% as a preservative and comes in multiple-dose vials, so it suppresses microbial growth between withdrawals. Sterile water has no preservative and is for single-dose use. Bacteriostatic water is contraindicated in neonates because of the benzyl alcohol.

How do I convert milligrams to units on an insulin syringe?

Divide the vial strength in milligrams by the diluent volume in millilitres to get the concentration, then divide your dose by that concentration and multiply by 100. A U-100 syringe reads 100 units per millilitre, so one unit is 0.01 mL. Critically, those units are volume markings only when the syringe is used for anything other than insulin.

What should I do instead?

Start with measurement. Advanced diagnostic testing shows which inflammatory, metabolic, hormonal and nutritional markers are actually out of range for you — and most people find there is real work to do there before an unapproved injectable is the best next step.

Keep Reading

Peptide Therapy at a BHRC Studio Near You

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References & Further Reading

U.S. Food & Drug Administration — Pharmacy Compounding Advisory Committee Briefing Document: Thymosin Alpha-1–Related Bulk Drug Substances, December 2024. fda.gov
U.S. Food & Drug Administration — December 4, 2024 Meeting of the Pharmacy Compounding Advisory Committee. fda.gov
U.S. Food & Drug Administration — Interim Policy on Compounding Using Bulk Drug Substances Under Section 503A (guidance), January 2025. fda.gov
U.S. Food & Drug Administration — Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. fda.gov
U.S. Food & Drug Administration — Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. fda.gov
World Journal of Virology — Dominari A et al. Thymosin alpha 1: A comprehensive review of the literature, 2020. pmc.ncbi.nlm.nih.gov
DailyMed / U.S. Food & Drug Administration — Bacteriostatic Water for Injection, USP — approved labeling. dailymed.nlm.nih.gov
DailyMed / U.S. Food & Drug Administration — Humulin R U-100 (insulin human) — label confirming 100 units/mL. dailymed.nlm.nih.gov
United States Pharmacopeia — General Chapter <797> Pharmaceutical Compounding — Sterile Preparations. usp.org
Centers for Disease Control and Prevention — Safe Injection Practices to Prevent Transmission of Infections to Patients. cdc.gov
U.S. Food & Drug Administration — Warning Letter — Wholesale Peptide, June 2026. fda.gov

Beverly Hills Rejuvenation Center. This content is for general education and does not create a physician-patient relationship or constitute medical advice. Thymosin alpha-1 is not approved by the FDA for any indication and is not currently eligible for compounding in the United States. Dosing figures are drawn from published clinical studies for informational purposes and are not a recommendation or a prescription. Candidacy, dosing, results and pricing vary by person and are confirmed at a free consultation. Reviewed by the BHRC clinical team.

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Thymosin Alpha-1 Dosage Guide: Immune Protocol & Reconstitution

1 · What thymosin alpha-1 is

2 · Where it stands with the FDA — the exact position

3 · Doses used in published studies