Thymosin Alpha-1
Also known as Zadaxin (thymalfasin)
Quick facts
- Researched for
- Immune support, inflammation, long-lasting illness or infection concerns and recovery after procedures
- Route or form
- Injection
- Evidence so far
- Tested in a hospital trial of critically ill patients; gut work is in mice.
- Not established
- Studies in certain illnesses do not prove it boosts immune health in everyone.
- Commonly researched
- 1.5 to 1.6 mg, twice weeklyPractitionerSee every range
- Where to get it
- At our partner, US Precision Peptides.Go to Next step
By the Learn Peptides editorial team · Updated · What changed: Drops approval claims for other countries that we could not confirm with a regulator. · How We Research
What people are researching it for
People are researching Thymosin Alpha-1 for immune support, inflammation, long-lasting illness or infection concerns, and recovery after procedures.
Regulate. Respond. Recover.
- What is Thymosin Alpha-1?
- a synthetic version of a naturally occurring thymic peptide made of 28 amino acids
- Checklist: 28 amino acids
- also called thymalfasin
- How does it work?
- Not written out in this text version.
- Common research use cases
- Not written out in this text version.
- How it's used in research
- Route: Subcutaneous (most common)
- Route: Sometimes used in cycles
- Route: Typically tracked for symptom response
- Common dosing: Often discussed around 1 to 1.6 mg twice weekly
- Common dosing: Some researchers use lower daily dosing
- Common dosing: Duration commonly 4 to 8 weeks
- Often combined with: General recovery protocols
- Often combined with: BPC-157 or TB-500
- Often combined with: Long-COVID / immune-support stacks
- There is no standardized dose or protocol. Research use should be thoughtful, tracked, and adjusted based on individual response.
- What users report
- Keep in mind: Results vary widely
- Keep in mind: Some users report no effect
- Keep in mind: Some report fatigue, GI upset, or immune-type flare reactions
- Keep in mind: Forum anecdotes are mixed and not the same as clinical proof
- Subtle or no noticeable ‘feeling’ at baseline
- Key takeaway
- It has a stronger clinical research history than many peptides discussed online, but community uses such as allergies, Long COVID, and general immune support remain experimental.
- The bottom line
- Thymosin Alpha-1 is one of the more intriguing immune-focused research peptides. The strongest forum themes are immune resilience, allergy support, and post-illness recovery, but responses are mixed, and careful expectations matter.
Reasons people look into Thymosin Alpha-1. An interest is not a promise that it works.
- Injury & recovery
- Gut health
- Immune support
Most talk is about steady immune health and long illness, not a quick, big feeling.
Community reports
Community discussion focuses on steadier immune function, chronic illness or infection-related concerns, inflammation, and recovery rather than a dramatic immediate feeling.
Community reports
Most people using thymosin alpha-1 are managing a chronic illness, especially ME/CFS, or supporting their immune system during an infection, usually through a doctor or rather than a gray-market seller. Results are mixed: some people notice steadier energy or clearer thinking, but flare-ups, crashes, and no effect at all are all common.
Human studies cover several immune-related conditions.
Thymosin Alpha-1 has been studied in people with several immune-related conditions.
An immune-modulating peptide, often described as a coach for the immune system rather than a blunt booster.
What this is based on
- Human researchStudied in people for this or a related question.
- Animal researchUseful for understanding a research question, but not the same as evidence in people.
- Community reportsWhat people describe noticing. Not proof of cause.
- Industry perspectiveCommentary from practitioners and the industry, based on experience. Not a study.
- Learn Peptides explanationOur own plain-English summary of the sources. It is not a source itself.
Studies in certain illnesses do not prove it boosts immune health in everyone.
Research in specific illnesses does not prove that it broadly “boosts” the immune system in everyone.
Safety notes
Tested in people. How many took part, for how long, and who they were still matter.
- You have trouble breathing or wheezing, or your face, lips, tongue or throat swell.
- You get hives away from the injection site, or feel severely dizzy or faint.
For these signs, call 911 or your local emergency number.
- Redness spreads, or heat, swelling or pain keeps growing where you injected.
- A lump keeps growing or does not go away, or you see pus or red streaks.
- You have a fever or chills, or feel sick all over.
- An autoimmune condition. It turns up immune activity, which can make things worse at first. The cited commentary says to avoid it in a severe active flare, such as new-onset type 1 diabetes, autoimmune hepatitis or vasculitis. In any flare, start it only with medical guidance.
- You take immune-suppressing medicine. Its immune-boosting effect could work against medicine that holds back the immune system. The cited commentary says to avoid it after an organ transplant.
- No data in pregnancy or breastfeeding, so the cited commentary avoids it there. Industry perspective
- Injections can sting more than other peptides. Industry perspective
- Small minority get mild headache, fatigue, or flu-like symptoms early on. Industry perspective
Questions to bring to your doctor
Only for the conditions this page cautions about. Bring this page with you.
- Could Thymosin Alpha-1 make my autoimmune condition flare?
- Could Thymosin Alpha-1 work against my immune-suppressing medicine?
Shows practitioner ranges, Singapore's Zadaxin dose and what people report, each with its source.
Commonly researched ranges, and how they were measured.
Commonly researched range for Thymosin Alpha-1
1.5 to 1.6 mg
twice weekly · Injection
Practitioner
All 6 ranges in our record
Each one is labeled with where it comes from. They are different ways of using Thymosin Alpha-1, not steps to follow in order.
Standard, general/seasonal immune support (tier one)
Practitioner- Amount per dose
- 1.5 to 1.6 mg
- How often
- Twice weekly
- Typical schedule
- 4-8 weeks for a seasonal/immune-support block; ongoing/no defined cycle for general longevity or post-surgery use
- Route
- Injection
Active issue / workhorse dose (tier two)
Practitioner- Amount per dose
- 1.5 to 1.6 mg
- How often
- Three to five times per week
- Typical schedule
- Not stated
- Route
- Injection
Clinical / hospital setting (tier three)
Practitioner- Amount per dose
- 1.5 mg
- How often
- Daily
- Typical schedule
- Short blocks
- Route
- Injection
Post-viral fatigue / T-cell exhaustion / long COVID / EBV
Practitioner- Amount per dose
- 1.5 mg
- How often
- Twice weekly
- Typical schedule
- Up to 24 weeks
- Route
- Injection
Recurrent / sinus infections
Practitioner- Amount per dose
- 1.5 mg
- How often
- Twice weekly
- Typical schedule
- 8-12 weeks
- Route
- Injection
Hepatitis B regimen
Prescription label (branded medicine)Zadaxin product information (Singapore)- Amount per dose
- 1.6 mg
- How often
- Twice weekly
- Typical schedule
- 6-12 months
- Route
- Injection
This is the label amount for the branded medicine Zadaxin. It is not a dosing instruction for other products.
From our visual summary
Community reports
Community reports, from the Learn Peptides visual summary. These lines sit beside the ranges above and are not merged with them.
- Common dosing
- Often discussed around 1 to 1.6 mg twice weekly
- Some researchers use lower daily dosing
- Duration commonly 4 to 8 weeks
There is no standard dose. Track how you respond, and change one thing at a time.
These ranges were last reviewed Sep 2026.
A peptide the thymus makes to train immune cells, talked about for immune balance.
Thymosin Alpha-1 is a naturally occurring peptide the thymus gland already produces to train and regulate immune cells. It's discussed for helping the immune system respond more accurately without overreacting, a distinction that comes up often for autoimmune conditions, where balance matters more than raw stimulation.
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