Thymosin alpha-1

What Thymosin alpha-1 does

Thymosin alpha-1 is a synthetic immune-signaling peptide approved in Singapore for hepatitis B and, with interferon, hepatitis C, but not in the US. Large sepsis and hepatitis C trials found no clear benefit; hepatitis B evidence remains uncertain. Immune reactions and unregulated injection quality are key concerns.

• Zadaxin is approved in Singapore for patients with chronic hepatitis B, and with interferon for hepatitis C, but not in the US. (Studied in a trial)
• In a small hepatitis B trial, six months of dosing gave a delayed virus response, though overall evidence is very uncertain. (Studied in a trial)
• Some users report fewer allergy symptoms and infections; others report feeling worse for a long time. (Reported by users)

Uses in the sources

• Zadaxin is approved in Singapore for chronic hepatitis B and, with interferon, hepatitis C. These overseas approvals are not FDA or EMA approvals. (Clinician-published) (source)
• Studied as an add-on in sepsis. The largest blinded trial found 28-day deaths of 23.4% with TA1 versus 24.1% placebo. (Studied in a trial) (source)
• Studied in hospitalized COVID-19 and dialysis patients. Trials are small, and reviews conflict; prevention and recovery benefits remain unproven. (Studied in a trial) (source)
• Studied with cancer therapy and vaccines. Immune-test or short-term response changes do not establish longer survival or fewer infections. (Studied in a trial) (source)
• People report use for long COVID, ME/CFS and allergies. Reports include both improvement and prolonged worsening. (Reported by users) (source)

Thymosin alpha-1 dosage

Typical reported dose: 1.6 mg twice a week for 26 weeks

• Hepatitis B: 26 weeks: 1.6 mg twice weekly; no dose escalation. twice weekly, under the skin. Studied in a trial. Studied in: Adults with chronic hepatitis B. (source)
• Hepatitis B: 52 weeks: 1.6 mg twice weekly; no dose escalation. twice weekly, under the skin. Studied in a trial. Studied in: Adults with chronic hepatitis B. (source)
• Hepatitis B: 0.8 mg: 0.8 mg SC six times weekly., then 0.8 mg SC twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Japanese adults with chronic hepatitis B. (source)
• Hepatitis B: 0.8 mg loading: 0.8 mg six times weekly., then 0.8 mg twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Adults in the 16-person hepatitis B pilot. (source)
• Hepatitis B: 1.6 mg: 1.6 mg SC six times weekly., then 1.6 mg SC twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Japanese adults with chronic hepatitis B. (source)
• Hepatitis B: 1.6 mg loading: 1.6 mg six times weekly., then 1.6 mg twice weekly for 22 weeks. six times weekly for two weeks, then twice weekly, under the skin. Studied in a trial. Studied in: Adults in the 16-person hepatitis B pilot. (source)

These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.

Work out syringe units with the dosing calculator

How to mix Thymosin alpha-1

Comes as: Lyophilized powder in a single-use vial.

Mixed with: The foreign product uses 1 mL of supplied sterile water for injection per 1.6 mg vial..

Common vial sizes: 1.6 mg. Common water amounts: 1 mL.

• These are foreign-product clinical-use instructions, not an FDA or EMA label.
• Do not mix Zadaxin with another medicine or reuse its single-use vial.

Before mixing: Indonesia product instructions specify 2-8°C for Zadaxin. This does not establish storage life for unregulated powders.

After mixing: Use Zadaxin immediately after mixing; no supported multiweek refrigerated beyond-use time was located.

Thymosin alpha-1 side effects and risks

Reported side effects

• Injection-site discomfort or redness: Foreign information reports <1% drug related events overall in over 2,000 people; no site specific rate., mild. Report persistent pain, swelling or redness; worsening local changes can signal infection. (source)
• Rash, joint pain or hand swelling: Described as rare in foreign product information; exact counts were not supplied., moderate. Stop dosing and seek assessment if symptoms spread or persist. (source)
• Liver-test flares during hepatitis B dosing: 22/316 in the Japanese trial, 11 at each dose; arm specific percentages not extracted., moderate. Needs liver tests and clinical review; jaundice, confusion or bleeding need urgent care. (source)
• Serious immune reaction with checkpoint therapy: One 2026 case involved fever, rash and multiple organ injury after sintilimab plus TA1., serious. Urgent assessment for fever, rash, breathing trouble or jaundice during cancer immune therapy. (source)
• Events during intensive-care treatment: TESTS: any event 66.4% versus 67.6% placebo; serious events 26.8% versus 29.3%., serious. These are all-cause events in critically ill patients, not TA1-attributed side-effect rates. (source)
• Worse fatigue, sleep or swollen glands: Self reports include worsening after 100 mcg once; no incidence or causality can be calculated., moderate. Do not assume a worsening reaction means the product is working. Seek assessment. (source)

Stop and get help if

• Trouble breathing, throat or face swelling, widespread hives or fainting after an injection: Stop dosing and get emergency care for a possible severe allergic reaction.
• High fever, rapidly spreading rash, chest tightness or new breathing trouble during cancer immune therapy: Seek urgent hospital assessment; severe immune toxicity and infection can look alike.
• Jaundice, confusion, vomiting blood or new severe abdominal swelling: Get urgent care for possible liver failure or bleeding.
• Worsening injection-site redness, warmth, pus or fever: Get prompt assessment for injection-related infection.

Who should avoid it

• pregnant: Human pregnancy safety is unknown. Foreign product information does not establish fetal safety.
• breastfeeding: It is unknown whether TA1 enters human milk or affects a nursing infant.
• tryingToConceive: Reproductive safety in humans is not established; this is a precaution, not evidence of infertility.
• under18: Safety and effectiveness below 18 are not established in the inspected foreign product information.
• other: Foreign product information contraindicates use after hypersensitivity to TA1 or its ingredients.
• other: Foreign instructions contraindicate deliberate immune suppression unless a specialist judges benefits outweigh risks.
• immunosuppressed: Low immune function from HIV or cancer differs from deliberate immune suppression. Trials used specialist care and do not establish routine self-use.
• autoimmuneDisease: Effects in active autoimmune disease are uncertain. Major sepsis trials excluded acute autoimmune disease.
• liverDisease: Hepatitis B dosing can cause liver-test flares. Cirrhosis or liver failure needs disease-specific monitoring.
• kidneyDisease: A small dialysis trial does not establish a general kidney-dose adjustment or long-term safety rule.
• activeCancer: TA1 has been studied with cancer drugs, but a severe immune reaction was reported with checkpoint therapy. Coordinate with oncology.
• testedAthlete: TA1 is not named in the 2026 list. Obtain a compound-specific ruling; the named thymosin beta-4 ban concerns a different peptide.

Interactions

• Other immune-suppressing drugs: Review the reason for immune suppression and the intended TA1 effect. Formal interaction studies are incomplete.
• Transplant immune-suppressing medicines: TA1 may oppose transplant immune suppression. Foreign instructions flag deliberate immune suppression as a contraindication.
• Immune checkpoint inhibitors: Severe multi-organ immune toxicity was reported with sintilimab plus TA1. Risk across this drug class is unknown.
• Interferon products: Studied together, but adds the risks of interferon; thyroid-function changes occurred in an older combination study.
• Vaccines: TA1 has been studied as a vaccine add-on. Sustained benefit is uncertain, and combining it without review can alter immune response.
• Other thymic or immune peptides: Check for duplicate TA1 exposure. Combining immune peptides has no established safety or interaction map.

Product quality risks

• FDA flags peptide impurities, uncertain characterization and immune-reaction risk for compounded TA1.
• Unregulated injections can have the wrong amount, unknown ingredients, particles, microbes or endotoxin.
• A purity percentage does not establish the amount per vial, sterility, endotoxin level or clinical safety.

What to expect

Major sepsis and hepatitis C trials found no clear benefit. Hepatitis B findings remain uncertain, and reviews reuse some of the same trial data.

Key studies

• Early injection dose study (1983): Short-lived immune-test changes did not establish an anticancer benefit. (source)
• Absorption and half-life (1999): Formulation affects exposure; a short blood half-life does not set an effective dosing interval. (source)
• Early hepatitis B pilot (1991): A tiny mixed-product pilot cannot isolate TA1 benefit. (source)
• Hepatitis B versus interferon (1996): This small trial did not show a clear advantage over interferon. (source)
• Hepatitis B: six or twelve months (1998): A delayed viral response favored six months of dosing in this small trial. (source)
• Hepatitis B placebo trial (1999): The placebo-controlled phase 3 trial did not confirm efficacy. (source)

Thymosin alpha-1 FAQ

• Is Thymosin alpha-1 FDA-approved? No FDA-approved TA1 product. FDA issued a December 7, 2020 warning over TA1 COVID claims. A committee vote or overseas approval is not US approval.
• How do people take it? Under the skin, twice weekly. 26 weeks. Source: studied in a trial.
• What's the difference between Thymosin alpha-1 and BPC-157? Thymosin alpha-1: an immune-signaling peptide with overseas approvals and mixed trial results. BPC-157: an experimental repair peptide with mostly animal evidence and a few small human reports. Why people pair them: reported in recovery or long-COVID stacks; no human trial located for the combination.
• Can I take it with BPC-157? Reported in recovery or long-COVID stacks; no human trial located for the combination. Combined safety is unknown, and several simultaneous drugs obscure the cause of benefit or harm. Source: reported by users. Ask a doctor before combining anything.
• Is it banned in sport? It is unclear (WADA 2026). TA1 is not named. S0 concerns substances with no approval anywhere; TA1 has overseas approvals. Beta-4/TB-500 is S2.3. Obtain an anti-doping ruling.
• How long does a mixed vial last? Use Zadaxin immediately after mixing; no supported multiweek refrigerated beyond-use time was located.