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Thymosin Alpha-1

Taken to support immune defenses

Thymalfasin (Zadaxin)

Match every finding to its exact substance, formulation, route and study population. A related molecule or approved medicine does not validate a catalog vial.

Animal / laboratory evidence · Human / product-specific records · Mechanistic / indirect records
Explore the evidenceWhy people take it
Compare this compoundRead original sources Community reports
Schematic illustration · View structure evidence

Simplified drawing of a chain of 28 amino acids

At a glance

Why people take it. And what backs it up.

  1. Strengthen immune defenses

    People report it, not studied

    The most common use: courses of twice-weekly shots, copying the drug’s label, hoping to fend off colds and infections.

    Sources (3)

  2. Recover faster when sick

    People report it, not studied

    Others take daily shots at the first sign of a cold, flu or infection, hoping to shorten it.

    Sources (2)

  3. Fight chronic infections

    People report it, not studied

    Practitioners and patients use it for Lyme disease, mold illness, chronic fatigue and long COVID, sometimes at high doses.

    Sources (4)

  4. Treat hepatitis B

    Approved abroad for hepatitis B

    Approved abroad as Zadaxin, for example in Singapore, to treat chronic hepatitis B; in one trial, 41% cleared signs of active virus versus 9% untreated.

    Sources (3)

  5. Help vaccines work

    Approved in Italy for weak immune systems

    In Italy it is approved to help the flu vaccine work in adults with weakened immune systems.

    Sources (3)

Evidence briefing

Sources checked

What the sources support.

Thymosin alpha-1 (thymalfasin; sold as Zadaxin in some markets) is a 28-residue thymic peptide. FDA briefing materials document country-specific medicinal-product authorizations, including Italy for use as an influenza-vaccine adjuvant in immunocompromised people and Indonesia for chronic hepatitis B; those approvals do not extend to US research-vial products. FDA has not approved it and identified route-dependent immunogenicity and peptide-quality concerns for compounding.

Keep in mind

Country, formulation, route and indication differ by national label; evidence or authorization for a named Zadaxin product does not establish safety, efficacy or approval for vendor vials or other proposed uses.

Identity and research status reviewRead the original sources

The research. What’s been studied.

  • Early human studies

    Immune signaling

    Modulates T-cell and other immune activity. This biological activity does not establish benefit for a broad range of infections or cancers.

  • Human evidence

    Chronic hepatitis B

    Approved abroad for chronic hepatitis B, for example as Zadaxin in Singapore, alone or with interferon. Not FDA-approved; the authorization does not extend to unrelated seller vials.

  • Human evidence

    Vaccine response

    Approved in Italy, as Zadaxin, to help the flu vaccine work in people with weakened immune systems. Effectiveness findings are limited and product-specific.

  • Early human studies

    Cancer add-on research

    Investigated alongside cancer treatment in some settings; this does not establish thymosin alpha-1 as a cancer treatment.

What do these labels mean?
  • Human evidence: approved-drug data or larger human studies, within the populations and uses studied.
  • Early human studies: small, preliminary or limited human studies.
  • Animal & lab studies: animal or laboratory findings that do not establish effects in people.
  • Unverified: a proposed use or claim without verified supporting clinical evidence.
How each claim was reviewed (4)

Reported effects and evidence.

A citation may support, qualify or correct a claim. Read the study scope; a laboratory result is not an established benefit in people. Each review covers a claim as it was first collected; the tiles above show the collection’s current wording.

  1. Preclinical immune mechanism

    Review of “Stronger T-cell immunity”

    Thymosin alpha-1 alters immune-cell signaling in experimental systems; clinical implications depend on disease and study.

    Limitations and applicability. Immune signaling changes do not establish universally stronger immunity or proven anticancer benefit.

    Original collected claim and review history

    Original title: Stronger T-cell immunity

    Helps T-cells mature and activates antiviral and anti-tumor immune signaling.

    Original label: proven. Preserved for traceability; the reviewed wording above qualifies this record.

    Record thymosin-alpha-1:benefit:1 · Annotated 2026-10-01 · Review method

  2. Human trials; jurisdictional approval claims need exact labels

    Review of “Hepatitis B and C treatment”

    Thymosin alpha-1 has been studied for chronic hepatitis. Show verified country, product and exact approved indication separately.

    Limitations and applicability. Country count and hepatitis C implication require country-specific current labels; trials alone do not establish approval.

    Original collected claim and review history

    Original title: Hepatitis B and C treatment

    Approved in about 35 countries, mainly as a treatment for chronic hepatitis B.

    Original label: proven. Preserved for traceability; the reviewed wording above qualifies this record.

    Record thymosin-alpha-1:benefit:2 · Annotated 2026-10-01 · Review method

  3. Older randomized human vaccine-response trial

    Review of “Better vaccine responses”

    An older randomized trial evaluated influenza-antibody responses in elderly men; general vaccine-enhancement claims need population-specific evidence.

    Limitations and applicability. Trial enrolled older men and measured antibody response; it does not establish broad infection protection in all immunocompromised people.

    Original collected claim and review history

    Original title: Better vaccine responses

    Boosted vaccine responses in people with weak immune systems.

    Original label: early. Preserved for traceability; the reviewed wording above qualifies this record.

    Record thymosin-alpha-1:benefit:3 · Annotated 2026-10-01 · Review method

  4. Cancer adjunct research; benefit unestablished

    Review of “Add-on to cancer treatment”

    Thymosin alpha-1 has been investigated with cancer therapies; identify each human trial separately from mechanistic tumor research.

    Limitations and applicability. Current verified paper includes mechanistic tumor models; being studied with chemotherapy is not proof of clinical cancer benefit.

    Original collected claim and review history

    Original title: Add-on to cancer treatment

    Studied alongside chemotherapy in some cancers, mainly outside the US.

    Original label: early. Preserved for traceability; the reviewed wording above qualifies this record.

    Record thymosin-alpha-1:benefit:4 · Annotated 2026-10-01 · Review method

The research in detail

Evidence category

Approved outside the US

Clinical studies have examined thymosin alpha-1 as an add-on in chronic viral hepatitis, cancer and vaccine-response research, with results that vary by condition and product. Foreign authorization is indication- and formulation-specific. FDA has not approved it and has raised immunogenicity and peptide-quality concerns for proposed compounded routes.

Evidence is assessed claim by claim above. Regulatory approval, study design, findings and relevance are separate questions; there is no single evidence score.

Risks and unknowns. What to know first.

Collected cautions follow. These are not an exhaustive or independently validated safety assessment; claim references do not automatically support every caution.

  • Generally well tolerated in trials; injection-site discomfort is most common.
  • Immune stimulation is a concern with autoimmune disease or organ transplants.

What people report

Show all 8 cautionsShow fewer cautions

Read this first: what “research use only” means

Published dosing records. What the label abroad says.

Historical label and trial records for the named product, route, population and indication. These records are not a personal schedule or a validated regimen for a catalog vial. Source attribution does not establish applicability.

Helping the flu vaccine work in adults with weakened immune systems (Italy’s approved use)

Zadaxin (Italy)

Fixed courseLabel abroad

Source: Zadaxin summary of product characteristics (AIFA, Italy; document dated 26/02/2026)

How
Injection under the skin or into a muscle
How often
Twice a week
How long
Two 4-week blocks: from the first flu shot (week 0), and again from week 8 to week 12

Dose, step by step

  1. Weeks 0–4 1.6 mg
  2. Weeks 8–12 1.6 mg
  • Each injection is one vial (1.6 mg). The label also says the dose is based on body size (900 mcg per square metre, which it calls the weekly dose) and lists doses from 1.32 mg to 1.87 mg by height and sex.
  • It is not to be used in children, or during pregnancy or breastfeeding.
  • In Italy, Zadaxin is approved only as an add-on to flu vaccination, not for hepatitis B.

Hepatitis B trial

Chronic hepatitis B: randomized controlled trial in 98 patients (Chien et al., Hepatology 1998)

Fixed courseClinical trial

Source: Chien et al., Hepatology 1998

Weeks 1–26
1.6 mg
How
Injection under the skin
How often
Twice a week
How long
26 weeks in the trial
  • A second group got the same dose for 52 weeks. At 18 months, 40.6% of the 26-week group had a complete response, against 26.5% of the 52-week group and 9.4% of untreated patients.
  • Another placebo-controlled trial of 1.6 mg twice a week for 6 months did not confirm a clear benefit (Mutchnick et al., 1999).

This schedule comes from the cited national product label. Authorization and availability can change: check the current local status and exact formulation. A research vial is not the labeled product.

These doses were tested in clinical trials under medical supervision. They aren’t approved for use, and a research vial is not the product that was tested.

Community protocols. Reported online. Not clinically validated.

Community reports Collection date: 30 Sep 2026

The most common protocol copies the Zadaxin label: 1.5–1.6 mg injected under the skin twice a week, usually for 4–12 weeks. Many clinics and users instead inject 300–500 mcg every day for 1–2 months, or 1–1.6 mg a day for 1–2 weeks while sick; outliers run from 800 mcg once a week to 5 mg a day (sometimes into a vein) for long COVID.

Not testedFrequently encountered in reviewed sources

Twice-weekly immune support (copies the drug label)

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
1.5–1.6 mg
How often
Twice a week, evenly spaced (some clinics: 2–3 times a week)
Route
Injection under the skin, usually the belly
How long
Usually 4–12 weeks (8–12 weeks, repeated 2–3 times a year, per Jay Campbell)
Cycle
One clinic: 8 weeks on, 4 weeks off. Some forum users run it only 1–2 weeks a month or only when sick
Mixing
10 mg research vial + 2–3 mL bacteriostatic water (about 3.3–5 mg per mL); clinics often dispense a ready-made 3 mg per mL vial
  • Copies the approved Zadaxin (thymalfasin) schedule of 1.6 mg twice a week; forums, Ben Greenfield and some pharmacies round it to 1.5 mg.
  • Often stacked with LL-37 or BPC-157 in ‘immune’, Lyme, mold or gut protocols.
  • A telehealth long-COVID page (HealthRX) uses the same dose for 12–24 weeks, but its study citations are unreliable (see flags).
  • The label dose itself is compiled elsewhere; this entry only records that community and clinic protocols copy it.
Sources (4)

Not testedCommon

Daily low dose (clinic vial or research vial)

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
300–500 mcg (some go up to 1–1.5 mg)
How often
Once a day
Route
Injection under the skin
How long
About 30–60 days (‘until the vial is empty’, about 1 month); vendor templates say 8–12 weeks
Cycle
One practitioner on Reddit cycles patients 30–60 days rather than year-round
Ramp
Vendor templates: 300 mcg a day in week 1, then 500 mcg a day. One Reddit user’s doctor started about 240 mcg (6 units) and built to about 1 mg (25 units) a day
Mixing
Compounded 3 mg per mL vial, 0.15 mL (450 mcg) a day; or 10 mg research vial + 2.5–3 mL bacteriostatic water (about 3.3–4 mg per mL; 500 mcg is about 12–15 units)
  • Tailor Made Compounding’s 5 mL, 3 mg per mL product was labeled 0.15 mL once a day until the vial is empty (about a month) or 1.5–1.6 mg twice a week; its patient sheet says ‘best prescribed to be taken once daily’.
  • A Reddit user who says they treat patients lists 500 mcg daily for ‘longevity’ and 500 mcg–1.5 mg daily for immune issues.
Sources (4)
Show all 8 protocolsShow fewer protocols

Not testedCommon

Acute illness burst (daily while sick)

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
1–1.6 mg a day (some 3.2 mg)
How often
Once a day
Route
Injection under the skin
Timing
Started at the first sign of illness. Ben Greenfield’s article says morning or before bed, on an empty stomach
How long
About 5–14 days, while sick
Cycle
Then stop, or taper to 0.8–1.6 mg 2–3 times a week (Greenfield) or twice a week for 4–6 weeks (Campbell)
  • Some users run it 5 days on, 2 days off.
  • Jay Campbell justifies daily ‘loading’ from COVID-19 and sepsis trials that dosed daily or twice a day.
  • One Reddit user took 1 mg a day for 4 days for an ear infection.
Sources (4)

Not testedSometimes seen

Lyme / chronic fatigue wide range (Holtorf)

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
300–2,000 mcg
How often
Anywhere from once a day to once a week
Route
Injection under the skin
How long
Not stated
Ramp
Adjusted to symptoms and immune lab markers (for example natural killer cell activity and viral or bacterial titers)
  • From Kent Holtorf’s 2017 conference slides on chronic Lyme disease, chronic fatigue and other chronic infections.
  • A Reddit user with chronic sinusitis said they followed the doses in these slides.
Sources (1)

Not testedSometimes seen

Every third day

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
1.5–2 mg
How often
Every third day (some every 3–4 days)
Route
Injection under the skin
How long
About 2 weeks for a viral infection; 3 months or longer for chronic conditions (A4M)
Mixing
A4M lists a 3 mg per mL, 5 mL vial; one user mixed a 10 mg vial with 3 mL bacteriostatic water
  • From the American Academy of Anti-Aging Medicine (A4M) ‘Peptide Therapy Handbook’ monograph, which gives 1.5 mg under the skin every third day.
  • One Reddit user wrote ‘1500mg every 3 or 4 days’, clearly meaning 1,500 mcg (1.5 mg).
Sources (3)

Not testedFringe

Low weekly dose (allergy season or ‘primer’)

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
About 750–1,000 mcg a week (for example 800 mcg per shot)
How often
Once a week (twice a week if symptoms are bad)
Route
Injection under the skin
How long
2–12 weeks
  • Used by otherwise healthy users as a seasonal ‘primer’ or for allergies; other forum members called these doses too low (‘half doses’).
Sources (2)

Not testedFringe

High-dose long COVID

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
About 1.4–5 mg a day
How often
Once a day (one user: 5 days on, 2 days off)
Route
Injection under the skin; one clinic sometimes gave it into a vein
How long
Up to a 90-day cycle
  • Craig Koniver told Andrew Huberman his clinic used 5,000 mcg (5 mg) a day for long COVID, sometimes intravenously.
  • A long-COVID Reddit user wrote ‘1.4g-2g’ a day (clearly mg), plus VIP three times a day, for 90 days.
Sources (2)

Not testedFringe

Compounded nasal spray

Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.

Frequency labels describe this collection, not a measured population. Contradictory records remain available.

Details and sourcesHide details
Dose
Not stated (products sold as 3 mg and 10 mg nasal sprays)
How often
Not stated
Route
Nasal spray
  • FDA’s 2024 review found a naturopathic clinic, a holistic wellness center and a hydration-drip lounge marketing thymosin alpha-1 nasal sprays. No per-spray dose or schedule was found.
Sources (1)

Where the numbers come from

The twice-weekly 1.6 mg schedule (often rounded to 1.5 mg) is copied from the Zadaxin (thymalfasin) label and its hepatitis B trials. The daily 450–500 mcg schedule traces to US compounding-pharmacy products, such as Tailor Made Compounding’s 3 mg per mL, 5 mL vial (‘0.15 mL once daily until the vial is empty’), which anti-aging clinics prescribed. Daily ‘while sick’ courses borrow from COVID-19 and sepsis trials that dosed daily or twice a day, and were popularized by Ben Greenfield and Jay Campbell. Kent Holtorf’s 300–2,000 mcg range comes from his Lyme and chronic-fatigue practice, and the 5 mg a day long-COVID dose from Craig Koniver’s clinic.

Research notes

1) Dose rounding: the label dose is 1.6 mg, but forums, Ben Greenfield and Tailor Made Compounding’s own dosing chart say 1.5 mg (its fact sheet says 1.6 mg); both circulate. 2) The Huberman Lab episode intro says thymosin alpha-1 was ‘re-allowed for prescription’ and ‘approved again’. FDA records do not support this: its advisory committee voted 17–4 against adding it to the compounding list (Dec 4, 2024), FDA’s April 2026 safety page still lists it, and it is in no 503A category on FDA’s list updated May 14, 2026. It is not FDA-approved. 3) Men’s Health (July 2026) says it is expected at a 2027 FDA meeting, but FDA’s announced agenda for the meeting before the end of February 2027 lists LL-37, GHK-Cu, dihexa, melanotan II and PEG-MGF, not thymosin alpha-1. 4) Several Reddit posts write mg or g where mcg or mg is meant (‘1500mg every 3 or 4 days’, ‘1.4g-2g’). 5) HealthRX’s long-COVID page (1.6 mg twice a week for 12–24 weeks) has unreliable citations: it calls NCT05350111 an ongoing thymosin alpha-1 long-COVID trial, but that registry number belongs to an adolescent cardiometabolic study, and its ‘2022 Italian cohort, N=218’ could not be verified. It is mentioned only in notes. 6) A patient blog (Diary of Recovery) says some members get autoimmune symptoms back if they use it while healthy, so they use it only during acute illness; anecdotal. 7) FDA’s 2024 review found clinics also sell it as 3 mg and 10 mg nasal sprays, with no stated per-spray dose. 8) Tailor Made Compounding, whose catalog is a dose source here, pleaded guilty in 2020 to distributing unapproved new drugs (the plea list named LL-37 and others, not thymosin alpha-1).

Measurement basics and calculator

Explore vial arithmetic

What it is. In plain English.

An immune-signaling peptide with country-specific medicinal products and indications.

A 28-amino-acid peptide first isolated from the thymus, the organ where T-cells mature.

It helps T-cells mature and activates immune signaling through toll-like receptors, generally strengthening responses against viruses and tumors.

Reviewed 2026-10-01.

Structure. What it really looks like.

Experimental

NMR structure of thymosin alpha 1 (sky blue), one chain shown on its own.

Thymosin alpha 1 (sky blue) on its own: all 28 amino acids, with the acetyl group at its start. It was measured in tiny detergent clusters (micelles) that imitate a cell membrane, and this is the first of the 20 shapes in the NMR entry. No partner protein is part of this structure.

2MNQ, Nepravishta et al., 2015. Rendered with Mol* (Sehnal et al., 2021) from RCSB PDB data (Berman et al., 2000).

Specs. The facts at a glance.

Length
28 amino acids
Sold as
  • Thymosin Alpha 1 10 mg
Regulatory status
Some national authorizations exist for specific thymalfasin products and indications. FDA materials document Zadaxin in Italy as an influenza-vaccine adjuvant for immunocompromised people and in Indonesia for chronic hepatitis B; the agency notes it could not independently verify every reported foreign approval. Not FDA-approved. Compounded and research-vial products are not covered by those authorizations.
Also known as
Thymalfasin (Zadaxin)

Sources. What this page rests on.

Every source behind this page, with what it says and when it was checked, is in the Source library.

Thymosin Alpha-1 in the Source library

Original overview and research notes · annotated 2026-10-01

Historical collection text. Read alongside the claim corrections above; identity or evidence qualifications may supersede this wording.

Immune system support

An immune-strengthening thymus peptide approved as medicine in dozens of countries.

A 28-amino-acid peptide first isolated from the thymus, the organ where T-cells mature.

It helps T-cells mature and activates immune signaling through toll-like receptors, generally strengthening responses against viruses and tumors.

Clinical trials support its use in chronic hepatitis B and C and as a vaccine-response booster in people with weak immunity. Results in sepsis and COVID-19 were mixed.

Original status record: Approved in a number of countries, mainly for hepatitis B or as a vaccine booster (in Italy, only to boost flu shots in people with weak immunity). Not FDA-approved; an FDA advisory panel voted against pharmacy compounding in 2024.

More in Immune system.

Glossary

NMR

Nuclear magnetic resonance. Measures molecules in solution with strong magnets and radio waves, and gives a set of likely shapes rather than one.

Full glossary

Glossary

Protein Data Bank (PDB)

The free worldwide archive of 3D structures of proteins and other molecules measured in experiments. Each entry has a four-character code, like 7KI0.

Full glossary