Thymosin Alpha-1
aka TA-1, Zadaxin
A peptide your thymus gland naturally makes to coordinate the immune system.
Technically · Thymic immune-modulating peptide
In one sentence
A natural immune-system thermostat — turns the response up when you're sick, down when it's overreacting.
— Like rebalancing the volume knob on your immune system. Approved in 35+ countries, used for hepatitis B/C.
Half-life
~2 hours
About 2 hours active — daily injections or twice-weekly long-term.
Dosing
Daily SubQ, often 2x/week long-term
How often you take a dose
Route
SubQ · IM
How it goes into the body
Status
FDA
Approved by the FDA for prescription use
What it is
Your thymus is a small immune organ behind your breastbone. It makes a peptide called Thymosin Alpha-1 that helps train and coordinate your T-cells (your immune system's soldiers). The synthetic version (Zadaxin) is approved as a hepatitis treatment in 35+ countries — not the US, but available via compounding pharmacies.
The full technical answer
A 28-amino acid peptide naturally produced by the thymus gland. FDA-approved as Zadaxin for hepatitis B/C and other immune conditions in 35+ countries (not US-approved but available via compounding). Acts as an "immune thermostat" — boosts immune response when underactive, calms it when overactive.
How it works
TA-1 works like a thermostat for your immune system. If your immune response is too weak (chronic infection, post-surgery, cancer), it turns it up. If it's overreacting (autoimmune, inflammation), it calms it down. It does this by maturing T-cells, modulating cytokines, and waking up natural killer cells.
The full technical answer
Activates and matures T-cells (CD4 and CD8), modulates cytokine production, enhances natural killer cell activity. Restores balance to dysregulated immune systems without overstimulation.
What the research says
Decades of clinical trial data for hepatitis B/C treatment. Multiple studies show benefit in chronic infection, post-surgical recovery, and immune dysregulation. Strongest safety profile of any longevity-tier peptide.
Sources: PubMed: Thymosin alpha 1 · Zadaxin clinical data
Common dosing ranges
- Range
- 0.5–1.6 mg per dose
- Frequency
- Daily SubQ, often 2x/week long-term
- Duration
- 4–6 week cycles or ongoing for chronic conditions
Sources: PubMed
How to take it
Practical guidance synthesized from clinical protocols, FDA labels, and clinician interviews. Always cross-check with a prescribing physician.
Best time of day
AM SubQ. Some users split AM + PM for chronic conditions.
With food or fasted
Doesn't matter for SubQ — bypasses the gut.
How long to cycle
General longevity use: 4–6 week cycles, 2 weeks off. Chronic conditions (hepatitis, immune dysfunction): ongoing per physician.
When to get off
NEVER use during an active autoimmune flare or with a new cancer diagnosis (immune surveillance accelerator). Otherwise, end cycles on schedule.
Administration
Side effects
Common
- Injection site reactions (mild)
- Generally well-tolerated
Serious / theoretical
- Contraindicated in active autoimmune disease
- Contraindicated in active cancer (immune surveillance accelerator)
Sources: PubMed
Notes
Bachmeyer includes TA-1 in his "4 Forever Peptides" longevity scaffold. One of the few peptides with FDA approval (in other countries) and decades of human safety data.
Further reading & listening
Where the experts go deeper.
Curated from the PeptideFacts expert directory — vetted YouTube channels, podcasts, books, and communities. No anecdote-only or supplier-affiliated picks.