Thymosin Alpha-1

• Week 1-2: Little to feel; some report brief tiredness after shots
• Week 2-4: Changes show in blood tests, not feelings
• Week 4-8: Some users report fewer, shorter colds
• Week 8-12: Course ends at 8-12 weeks; then 4 weeks off
• Side effects: Usually mild soreness; 911 for allergy; hepatitis B: see Side effects

More on each stage

Week 1-2

Each shot peaks in the blood about 2 hours later and is back to normal levels within 24 hours. Its effects are on immune cells, so do not expect to feel a clear change. Some users report brief tiredness after a shot, which they put down to immune activity.

Week 2-4

In older adults given it alongside a flu shot, researchers checked the boost to antibodies 3-6 weeks after the vaccine. Changes like this show up in blood tests, not in how you feel.

Week 4-8

Users report fewer colds and shorter ones, and less tiredness while fighting an infection.

Week 8-12

Your course ends between weeks 8 and 12; then take 4 weeks off. In hepatitis B trials, many responses showed up a year or more after the last dose.

Side effects

Usually mild: soreness or redness where you inject. Rash, aching joints with swollen hands, or temporary muscle loss are rare. Stop and get help for any sign of an allergic reaction.

Based on what people report in the community sources below. Results vary, and many responses are anecdotal.

• Treats chronic hepatitis B

  Clinical trial

  In three controlled trials pooled on the Zadaxin label (223 people), 36% of people given 1.6 mg twice a week for 6 months had cleared the main virus markers a year later, compared with 19% given placebo or no treatment.12

• Helps interferon treat hepatitis C

  Clinical trial

  Pooled on the label, 22.4% of people given thymosin alpha-1 with interferon still had normal liver tests 6-12 months after treatment, compared with 9.3% given interferon alone.1

• Stronger response to the flu vaccine

  Clinical trial

  The researchers who ran the trials in older adults report that it strengthened flu vaccine responses. Their double-blind trial split 90 men aged 65-99 between thymosin alpha-1 and a placebo, both given alongside the vaccine, and saw no toxicity in either group. In a pilot in people on kidney dialysis, those who also got thymosin alpha-1 had better antibody levels at day 21, with no side effects linked to it.678

• Severe infection (sepsis)

  Clinical trial

  In a trial of 361 people with severe sepsis, fewer of those given thymosin alpha-1 died within 28 days (26.0% vs 35.0%). Neither of the two sepsis trials found extra safety problems with it.910

• Restored T cells in severe COVID-19

  Human study

  In a look-back study of 76 people with severe COVID-19 in Wuhan, fewer of those given thymosin alpha-1 died (11.1% vs 30.0%), and their T-cell counts recovered.11

• Add-on during cancer treatment

  Clinical trial

  The Zadaxin label lists use alongside chemotherapy to support immunity, based on trials in lung cancer, melanoma, and liver cancer that reported better immune markers and survival.1

• Fewer and shorter colds

  Community report

  Users report fewer colds, shorter upper-respiratory infections, and less tiredness when sick.12

What it has been studied for

• Immune signalling: activates dendritic cells, T cells and NK cells45Animal/lab study
• Chronic hepatitis B, alone or with interferon (approved use of Zadaxin abroad)12Clinical trial
• Chronic hepatitis C, with interferon (approved use of Zadaxin abroad)12Clinical trial
• Immune support during chemotherapy for several cancers1Clinical trial
• Boosting flu vaccine response in older adults and people on dialysis68Clinical trial
• Severe infection (sepsis), as an add-on in hospital patients910Clinical trial
• Severe COVID-19 with low T-cell counts11Human study
• Fungal lung infection (aspergillosis) after a bone marrow transplant, in mice5Animal/lab study

Thymosin alpha-1 is a chain of 28 building blocks (amino acids). It was first found in the thymus, a gland behind the breastbone where T cells, a key type of white blood cell, learn their job. It acts as a messenger to immune cells rather than killing germs itself. In lab studies, it switches on the immune system's scouts (dendritic cells) through special sensors. It also helps T cells and natural killer cells, another type of immune cell, do their work. The label says the exact way it works is not fully understood.

Peak

About 2 hours after an under-the-skin shot.

Half-life

About 2 hours in the blood.

Cleared

Back to normal blood levels within 24 hours. It does not build up with repeated doses. About a third to a little over half of each dose (31-60%) leaves in the urine.

Half-life is how long it takes the body to remove half of a dose.1

Twice a week. Any time of day. Keep 3-4 days between doses and use the same two days each week. Every week, for example Monday and Thursday. Units are for a 10 mg vial mixed with 2 mL water (5 mg per mL).

• Most common · labeled twice-weekly dose

  1.6 mg subcutaneously twice a week

  This is the Zadaxin dose for chronic hepatitis B: 1.6 mg under the skin twice a week, with the days a few days apart, continued for months.2↗

• Standard immune support (not tested in trials)

  1.5 mg under the skin, twice a week, for 8-12 weeks. This copies the label dose, and the store dose of 1.6 mg sits at the same level.12

• Daily low dose (not tested in trials)

  300-500 mcg under the skin, once a day, for 4-8 weeks. With this vial mix, that is 6-10 units a day. The label does not use daily dosing.12

• At the start of an illness (not tested in trials)

  1.6 mg once a day for 3-5 days, then twice a week, for 2-4 weeks in all.12

• Long-term maintenance (not tested in trials)

  1.5 mg once a week, with 1 month off after every 3 months on.12

Research protocols

• Zadaxin label: hepatitis B

  1.6 mg (900 mcg per square metre of body surface) under the skin, twice a week, for 6 to 12 months. People under 40 kg get 40 mcg per kg. This is the store protocol's dose and frequency.12

• Zadaxin label: hepatitis C

  1.6 mg under the skin, twice a week, for 12 months, together with interferon.2

• Zadaxin label: cancer

  1.6 mg under the skin on various schedules for 6 months, or between chemotherapy cycles. Some trials used 1 mg a day on days 8-11 and 15-18 of each chemotherapy cycle.1

• Flu vaccine trials

  Older men: 900 mcg per square metre under the skin, twice a week for 8 doses, alongside the vaccine. Dialysis pilot: 3.2 mg or 6.4 mg given with the vaccine.68

• Sepsis trials (hospital patients)

  1.6 mg under the skin twice a day for 5 days, then once a day for 2 days (ETASS), or 1.6 mg every 12 hours for 7 days (TESTS).910

• Highest doses tested in people

  The label reports no adverse reactions at up to 16 mg twice a week for 4 weeks. That is ten times the usual dose, and it is not a reason to take more.1

Zadaxin is approved for specific hepatitis treatment in some countries. It is not a general immune booster you can self-prescribe, and a research vial is not that medicine. People who are on purpose immunosuppressed, including many transplant patients, were called out as a group that should not use it unless a doctor decides the benefit outweighs the risk.

Dosing guidance built from the cited research and community reports. It is not a prescription.

On

8-12 weeks

Break

4 weeks

A full course at the store pace takes 3–4 vials. A mixed vial keeps for up to 90 days.

Why the break helps

No study has tested whether breaks help. The drug itself does not build up: blood levels return to normal within 24 hours of each dose. In hepatitis B, the benefit often showed up 12 months or more after treatment ended, so the effect seems to outlast the shots. A 4-week break after each course limits nonstop use of a product with no long-term data in healthy people, and lets you judge whether it was helping.

Common

• Soreness, redness, or a small bump where you injected. The label says this is the most common side effect, and it is mild.

  What to do Rotate sites and use a fresh syringe every time. If redness spreads or gets hot and painful, treat it as an infection (see below).

• Brief tiredness after a shot (reported by users)

  What to do Rest. If it lasts more than a few days, stop and talk to a doctor.

• Rare, per the label: a rash, aching joints with swollen hands, or temporary muscle loss

  What to do Stop thymosin alpha-1 and tell your doctor. Do not restart unless they agree.

Stop and get help

• Allergic reaction: hives, swelling of the face, lips, or throat, trouble breathing, or feeling faint. The FDA warns compounded thymosin alpha-1 may trigger an immune reaction.

  What to do Stop and call 911 (or your local emergency number) right away.

• If you have hepatitis B: yellow skin or eyes, dark urine, severe tiredness, or pain under the right ribs. The label warns that liver enzymes can briefly flare during treatment.

  What to do Get medical care the same day. Hepatitis B should only be treated with your doctor.

• Infection at the injection site: redness that spreads, heat, pus, red streaks, or fever

  What to do Stop injecting and see a doctor the same day.

Do not use if

• You have had an organ transplant or take medicine on purpose to suppress your immune system. The label says not to use it unless the benefit clearly outweighs the risk.
• You have had an allergic reaction to thymosin alpha-1 or any part of the injection.
• You are pregnant or breastfeeding: the label allows pregnancy use only when the benefit clearly outweighs the risk, and urges caution when breastfeeding.
• You are under 18: safety has not been established.
• You have hepatitis, cancer, or another serious illness, unless your doctor manages it. A research vial is not Zadaxin and is no substitute for treatment.

Sources3

Storage

Keep it

Keep the mixed vial in the fridge (2-8 °C), upright and away from light. Never leave it in a hot car.

How long

Use within 90 days of mixing. A mixed vial kept in the fridge holds its strength for 60-90 days, then slowly starts to lose potency. Wipe the rubber top with an alcohol swab before every draw.

Drawing your dose

Syringe: a 0.5 mL (50-unit) U-100 insulin syringe. Doses above 50 units (up to 64 here) need a 1 mL (100-unit) syringe.

1. Each unit line on a U-100 insulin syringe holds 50 mcg. Draw to the 32-unit line for 1.6 mg.
2. For the last dose in a vial, turn the vial upside down and keep the needle tip just inside the stopper so you can reach the last drops.
3. Before every draw, hold the syringe at eye level, flick out air bubbles, and push the plunger back to the exact line.
4. Pinch a fold of skin, insert the needle at 45 to 90 degrees, push slowly, and wait a few seconds before pulling out.
5. Do not mix it in the same syringe with another peptide or medicine. The Zadaxin label says it should not be mixed with any other drug.
6. Use a new sterile syringe every time and never share one.

• Epithalon

  Russian researchers paired a thymus-gland extract with a pineal-gland extract for older people, on the idea that both glands decline with age, and reported lower death rates in a long-term study. Those were the extracts Thymalin and Epithalamin, not thymosin alpha-1 or Epithalon. Wellness clinics now combine the two, but no study has tested this pair.1415

• BPC-157

  In a niche community stack for mold illness (CIRS), users combine thymosin alpha-1, BPC-157 and VIP, and describe the stack as immune modulation with gut healing. This is a community report only; no trial of this stack is cited.12

Interactions

• Transplant medicines and other drugs that suppress the immune system on purpose (for example tacrolimus, cyclosporine, mycophenolate)

  Thymosin alpha-1 is meant to strengthen immune responses, which works against these medicines. The label says not to use it in people who are deliberately immunosuppressed unless the benefit clearly outweighs the risk.

  What to do Do not use it unless your transplant or specialist doctor approves.

• Steroids and other immune-calming medicines for autoimmune disease (for example prednisone, methotrexate, adalimumab)

  The label urges caution when combining it with other drugs that change the immune system, and in a lab test it blocked the steroid dexamethasone from killing thymus cells. Interactions have not been fully studied.

  What to do Ask the doctor who prescribes these medicines first. Never stop a prescribed medicine to switch to a peptide.

• Interferon and cancer treatments, including chemotherapy and immunotherapy

  Doctors have used it alongside these treatments, but always under supervision, and the label urges caution with other immune-changing drugs.

  What to do Only use it during these treatments if your specialist agrees.

• Other peptides or medicines in the same syringe

  The label says thymosin alpha-1 should not be mixed with any other drug.

  What to do Draw and inject it on its own, with its own syringe.

Sources

1. 1Zadaxin (thymalfasin) full prescribing information, as reproduced by RxList: pharmacokinetics, dosing, safety, trial tablesDrug label
2. 2Singapore National Drug Formulary: Zadaxin 1.6 mg dosing and contraindicationsDrug label
3. 3FDA: Certain bulk drug substances for compounding that may present significant safety risks (thymosin alpha-1 entry)Reference
4. 4Dominari et al., Thymosin alpha 1: a comprehensive review of the literature, World J Virol 2020Review
5. 5Romani et al., Blood 2004 (thymosin alpha-1 activates dendritic cells through toll-like receptors; mouse aspergillosis)Study
6. 6Gravenstein et al., J Am Geriatr Soc 1989 (flu vaccine with thymosin alpha-1 in 90 older men, double-blind)Clinical trial
7. 7Ershler, Gravenstein and Geloo, Ann N Y Acad Sci 2007 (thymosin alpha-1 with flu vaccine in older people: trial summaries)Review
8. 8Carraro et al., Vaccine 2012 (Zadaxin with H1N1 flu vaccine in dialysis patients, pilot)Clinical trial
9. 9Wu et al., Crit Care 2013 (ETASS: thymosin alpha-1 in 361 people with severe sepsis)Clinical trial
10. 10Wu et al., BMJ 2025 (TESTS: placebo-controlled trial in 1,106 people with sepsis)Clinical trial
11. 11Liu et al., Clin Infect Dis 2020 (thymosin alpha-1 in 76 people with severe COVID-19, retrospective)Study
12. 12Peptide Protocol Wiki: Thymosin alpha-1 community protocols and reports (80 reports)Community
13. 13Peptide Protocol Wiki: Thymosin alpha-1 dosing, timing and storageCommunity
14. 14Khavinson and Morozov, Peptides of pineal gland and thymus prolong human life, Neuro Endocrinol Lett 2003Study
15. 15TrimRX: Epithalon dosing protocol (notes clinics combine it with thymosin alpha-1)Practitioner

Where people discuss it

• Singapore NDF — Zadaxin
• r/Peptides (subreddit)

Some peptides, like semaglutide (Ozempic and Wegovy), are FDA-approved medicines. Most of the peptides people research are not. That label sounds like the FDA tested something and turned it down. Usually it means something else: nobody has paid for the studies the FDA needs to see. Here is why.

The FDA doesn’t test drugs. Companies do.

The FDA does not run its own drug tests. A company that wants to sell a new medicine has to test it first, and pay for it. It studies the drug in animals, then in people: first 20 to 100 volunteers, then a few hundred, then up to 3,000. Then it sends all the results to the FDA. FDA scientists review them and decide whether the benefits outweigh the risks.

So approval always starts with a company asking for it. If no company applies, the FDA has nothing to review, however promising the research looks.

Those studies cost about a billion dollars

A study in the medical journal JAMA estimated that bringing one new drug to market costs a typical company about $1.1 billion. That figure includes the money spent on drug ideas that failed along the way, because many drugs that start human testing never make it.

A patent is how a company earns that money back

A patent is a right the government gives an inventor. For up to 20 years from the day the inventor applies, nobody else may make or sell the invention without permission.

For a drug company, that right is what makes the billion-dollar bet worth it. While the patent lasts, the company is the only seller, so it can charge enough to pay back the studies and the failures. When the patent runs out, other companies can sell cheap copies, called generics, and the price drops.

The FDA adds a shorter shield of its own. For 5 years after a brand-new drug is approved, no copycat version can apply for approval. That helps, but it is much shorter than a patent can last.

Why most peptides can’t be patented

To get a patent, an invention has to be new, and it has to be something people made, not something found in nature. Most popular peptides fail one test or both.

They come from nature. Many are copies or small pieces of molecules your body already makes. KPV is a 3-building-block piece of the hormone that tans your skin. BPC-157 is copied from a protein in stomach juice. In 2013 the US Supreme Court ruled that something that exists in nature, like a human gene, cannot be patented just because someone found it and pulled it out.

They aren’t new anymore. Many were first described in research papers decades ago. Scientists were already testing KPV in the 1980s. Once something has been published, it no longer counts as new, so nobody can patent it now, and any patents from back then have long since run out.

Without a patent, a company that paid for the studies would soon face rivals selling the same peptide without having paid for any research. Few companies will spend a billion dollars on a product anyone can copy. So nobody goes first, and the large human studies never happen.

The workaround: change the molecule

Drug companies do make peptide medicines, but they change the peptide first. A changed molecule is a new invention, so it can be patented. Semaglutide is a lab-made version of GLP-1, a gut hormone your body releases after meals, changed so one shot lasts a week. Tesamorelin (Egrifta) is the body’s own growth-hormone signal with a small fatty chain added. Both went through the full studies, and both are FDA-approved.

The natural versions, and the many peptides nobody has changed and patented, stay where they are: studied in labs and animals, used by the biohacking community, and never put through large human trials.

What this means for you

When a peptide is “not FDA-approved,” it usually means no company has paid for the large human studies. It does not mean the FDA tested it and found it harmful.

It also does not mean it is proven safe or proven to work. Without those studies, nobody knows the best dose for sure, or what rare or long-term side effects it may have. And the FDA does not check research peptides for purity or strength the way it checks approved medicines. That is why this page labels every finding by the kind of study behind it, and lists who should not use it.

Sources for this section

1. 1FDA: How drugs are developed and approved (the FDA does not test drugs; companies submit the evidence)
2. 2FDA: The drug development process, step 3: clinical research (study sizes for each phase)
3. 3Wouters, McKee & Luyten, JAMA 2020, corrected 2022: median cost to bring a new drug to market, $1.14 billion
4. 4US patent law, 35 U.S.C. § 154: a patent lasts 20 years from the filing date
5. 5FDA: Frequently asked questions on patents and exclusivity (5-year new chemical entity exclusivity)
6. 6US Supreme Court, Association for Molecular Pathology v. Myriad Genetics (2013): naturally occurring genes cannot be patented