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№ 030

Thymosin Alpha-1 (Tα1)

Immune-system peptide. Approved in many countries for hepatitis B/C and as adjunct to chemotherapy. Used here for chronic immune issues and post-illness recovery.

Immune
Evidence: Moderate

Thymosin Alpha-1 (Tα1): Immune-system peptide. Approved in many countries for hepatitis B/C and as adjunct to chemotherapy. Used here for chronic immune issues and post-illness recovery. Thymosin Alpha-1 is the immune-system peptide.

FDA ⓘ
Not approved
WADA
Not banned
Typical dose
1.6 mg sub-q
Half-life ⓘ
~2 hours
Route ⓘ
Subcutaneous
Schedule
1-2x weekly
In plain English

Thymosin Alpha-1 is the immune-system peptide. Approved in many countries for hepatitis and as adjunct to chemotherapy. Used here for chronic immune issues, post-illness recovery, or as a winter immune-support tool.

Status & legalityWhat do these mean? →
Natty? ⓘ
Not natty
FDA ⓘ
Not approved

Not FDA approved in the U.S. Has orphan drug status for some indications. Approved in 35+ countries (sold as Zadaxin) for hepatitis B/C and chemotherapy adjunct.

Compounding ⓘ
Not on 503A list

Its nomination was withdrawn in 2024, and FDA's advisory committee voted against including it in December 2024. It is not on the 503A list and is not scheduled for another review.

WADA ⓘ
Not listed

Interpretation varies, falls outside explicit S2 listing.

Prescribed ⓘ

Yes outside the U.S., prescribed by hepatology / oncology providers in countries where Zadaxin is approved.

Who it's for

  • →Users with chronic immune issues
  • →Post-illness recovery support
  • →Cancer / hepatitis-adjunct context under medical care

What to expect

  1. Week 1

    Subtle. Energy / immune-feel often shifts first.

  2. Week 4

    Chronic-illness markers improve in clinical contexts.

  3. Week 8

    Plateau. Cycle off.

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How it works (mechanism)

28-amino-acid peptide derived from prothymosin alpha. Activates Toll-like receptors (both TLR2 and TLR9) on dendritic cells, broadly enhancing T-cell-mediated immune responses without direct antigen specificity.

Dosing protocol

Members only

Stacks well with

Members only

Side effects

01Generally well tolerated
02Mild injection-site irritation

When NOT to use

  • ⚠Active immunosuppression therapy (talk to provider)
  • ⚠Pregnancy / nursing

Bloodwork to monitor

  • • CBC if running long term

Common mistakes

  • • Treating it like an acute immune fix
  • • Skipping cycle breaks
  • • Underdosing for chronic conditions

What it actually is

Thymosin alpha-1 is a 28-amino-acid peptide originally isolated from the thymus, the gland that trains your immune system's T cells. Unlike most peptides here it is an approved medicine in a large number of countries — though not the United States — for hepatitis B and C and as an adjunct in cancer treatment and vaccination. It has a substantial clinical literature: 35 randomised trials and 49 indexed human-trial records.

It acts largely through Toll-like receptor signalling on dendritic cells, the cells that present threats to the rest of the immune system. The effect is described as modulating rather than stimulating: it appears to improve T cell maturation and function and to shift immune responses toward a more effective pattern, rather than simply turning the immune system up. That distinction matters, because a general immune stimulant would be a bad idea in autoimmune disease, and this one is used in contexts where the immune response is failing rather than overactive.

Forms, and which is which

Zadaxin (pharmacy, outside the US)The approved indications

Approved in many countries for hepatitis B and C and as an immune adjunct. Manufacturer product with assured identity.

Verdict: The reference form where it is available.

Lyophilised powder, subcutaneousHow US use happens

Research-chemical or compounded supply, since there is no US approval. Identity unverified in the research-chemical case.

Verdict: The common route in the US, with the usual caveats.

Thymalin and other thymic extractsThe older, cruder relatives

Whole-gland extracts rather than a defined single peptide, used mainly in Russian and Eastern European practice.

Verdict: A mixture rather than a molecule — different proposition.

Oral thymic supplementsNothing

A 28-amino-acid peptide is not absorbed intact from the gut.

Verdict: Not plausible by the route claimed.

What it is claimed to do, graded

Improves outcomes in chronic hepatitis B and CStrong

The basis for approval across many countries, supported by randomised trials and meta-analyses.

Improves vaccine response in immunocompromised patientsModerate

Studied in dialysis and elderly populations with reasonable randomised support.

Adjunct in cancer treatmentModerate

Used alongside chemotherapy in several countries, with trial support that is real and mostly not from large Western programmes.

Helps sepsis and severe infectionLimited

Studied with mixed results. Interesting mechanistically, not established.

Restores immune function in healthy adultsNone shown

Most non-clinical use is this, and it has not been studied. An immune modulator in someone whose immune system is working normally has no demonstrated benefit.

Grades describe how much human evidence exists for that specific claim, not whether it will work for you or whether it is safe.

Pros and cons

Pros
  • • Genuinely approved in many countries, on real trial evidence
  • • A large clinical literature by the standards of this catalog — 35 randomised trials
  • • Very well tolerated across decades of clinical use
  • • Modulates rather than simply stimulates, which is the safer profile
Cons
  • • Not FDA approved, so US supply is compounded or research-chemical
  • • The evidence is in specific patient populations, not healthy adults
  • • Immune modulation is not obviously desirable if your immune system is already functioning
  • • Expensive relative to most peptides
  • • Autoimmune disease is a genuine caution, not a formality

When to stop

  • • Any autoimmune symptom appearing or worsening: joint pain, rashes, unexplained fatigue
  • • Injection-site reaction that spreads
  • • You have started immunosuppressant therapy for anything
  • • No measurable change in the marker you started it for

Interactions

Immunosuppressant therapyCaution

Working against the intended effect of the other drug. This matters most in transplant patients and treated autoimmune disease.

Autoimmune diseaseCaution

Modulating immune function where the immune system is already attacking the body is unstudied and could go either way.

VaccinationCompatible

Studied as a vaccine adjunct in immunocompromised populations, which is one of its better-supported uses.

ChemotherapyMonitor

Used as an adjunct in several countries, and that should be an oncologist's decision rather than an addition made independently.

CorticosteroidsMonitor

Opposing effects on immune function.

Is this for you?

Probably worth reading further if
  • • People with a specific immune-related diagnosis working with a clinician
  • • Anyone in a country where it is an approved, prescribed medicine
Skip it if
  • • You have an autoimmune disease
  • • You are on immunosuppressants or post-transplant
  • • You are pregnant or nursing
  • • Your immune system is working normally — that population has not been studied

The one number

35 randomised and 49 indexed human-trial records, and approved in many countries though not the US
Pepdex evidence index, PubMed; World J Virol 2020 comprehensive review (PMID 33362999)

Sources for the claims above

Drug & supplement interactions

  • ⚠Immunosuppressants (cyclosporine, tacrolimus, biologics): may counteract Tα1's immune-enhancing effect
  • ⚠Vaccination: may enhance vaccine response
  • ⚠Limited published interaction data outside oncology / hepatitis contexts

Community patterns

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AI Coach, live sample
Member answer
is 250mcg of bpc enough for a knee injury?
For a knee, is the standard working dose and a solid place to start. The trick with BPC is consistency, give it weeks, not days. , run it , and don't drop below , results tend to fall off under that line. If nothing's moved by week 3, that's when earns its place.
how much bac water for a 10mg reta vial?
is the standard play for a 10 mg reta vial. That gives you , clean unit math across the whole titration: on a 100-unit insulin syringe. Run instead if you want fewer, more concentrated shots. Most people titrate up over , and that mix keeps the numbers cleanest.
what should i track on bloodwork for tirzepatide?
Lipid panel, ALT/AST (liver enzymes), and an A1C, baseline before you start then every 3 months. If you've got metabolic-syndrome history, add fasting glucose and insulin so you can actually watch insulin sensitivity improve. You don't need a big hormone panel for a GLP-1.

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Frequently asked

What is Thymosin Alpha-1 (Tα1)?+
Thymosin Alpha-1 is the immune-system peptide. Approved in many countries for hepatitis and as adjunct to chemotherapy. Used here for chronic immune issues, post-illness recovery, or as a winter immune-support tool.
Is Thymosin Alpha-1 (Tα1) FDA approved?+
Not FDA approved in the U.S. Has orphan drug status for some indications. Approved in 35+ countries (sold as Zadaxin) for hepatitis B/C and chemotherapy adjunct.
Is Thymosin Alpha-1 (Tα1) legal?+
Thymosin Alpha-1 (Tα1) is not FDA-approved, so there is no approved prescription version. Most supply is sold as "research only" by peptide vendors. A compounding pharmacy may only use substances the FDA permits for compounding, and many research peptides are not permitted — do not assume a compounded prescription is available. Possession is generally not criminalized but distribution without authorization may be. Verify local laws.
Is Thymosin Alpha-1 (Tα1) banned by WADA?+
Thymosin Alpha-1 (Tα1) is not currently on the WADA prohibited list. Interpretation varies, falls outside explicit S2 listing.
Are you still natty after taking Thymosin Alpha-1 (Tα1)?+
No. Thymosin Alpha-1 (Tα1) is a performance-enhancing peptide and would disqualify a strict natty claim.
Do doctors prescribe Thymosin Alpha-1 (Tα1)?+
Yes outside the U.S., prescribed by hepatology / oncology providers in countries where Zadaxin is approved.
What's the typical dose of Thymosin Alpha-1 (Tα1)?+
Dosing depends on your goal, experience, and tolerance. The full Thymosin Alpha-1 (Tα1) protocol (dose, frequency, and how to titrate) is in the members section on the entry page.
What are the side effects of Thymosin Alpha-1 (Tα1)?+
Common side effects include: Generally well tolerated; Mild injection-site irritation. Less common effects and full safety details are on the entry page.
How long until Thymosin Alpha-1 (Tα1) starts working?+
Subtle. Energy / immune-feel often shifts first.
What can you stack with Thymosin Alpha-1 (Tα1)?+
Thymosin Alpha-1 (Tα1) is commonly combined with complementary compounds. The full stacking protocol (what to pair, dosing, and timing) is in the members section on the entry page.
Where do people get Thymosin Alpha-1 (Tα1)?+
Pepdex does not sell, ship, or recommend suppliers. Thymosin Alpha-1 (Tα1) is not FDA-approved; prescription versions require licensed clinical care, and "research only" markets carry real legal and quality risks. /coa explains how to verify a Certificate of Analysis and /guides/scam-vendor-spotting covers the red flags.
Thymosin Alpha-1 (Tα1) vs LL-37, which is better?+
Thymosin Alpha-1 vs LL-37: immune modulator vs direct antimicrobial peptide. Different jobs in the same system. Full head-to-head comparison: https://pepdex.co/compare/thymosin-alpha-1-vs-ll-37

Common questions about Thymosin Alpha-1 (Tα1)

Head-to-head with Thymosin Alpha-1 (Tα1)

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Thymosin Alpha-1 (Tα1) vs LL-37 →

Tracked alongside Thymosin Alpha-1 (Tα1)

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Thymalin

Used to rebuild a weakened immune system, mainly in older or post-illness patients. A polypeptide complex extracted from calf thymus and distinct from Thymosin Alpha-1, used in Russian and Eastern European clinical practice for immune restoration in elderly patients and post-illness recovery.