Thymosin Alpha-1 Reconstitution Calculator
Thymosin Alpha-1 has published human doses, and an approval that does not reach the United States. As thymalfasin, marketed as Zadaxin, it is registered as a prescription medicine in a number of countries, principally in Asia, Latin America and parts of Europe, for chronic hepatitis B and C and as an immune adjuvant. The FDA has never approved it, and its clinical development programme, phase III in hepatitis C and phase II in hepatitis B, never produced a US approval. It is a 28-amino-acid peptide given by subcutaneous injection. Every figure in the published range below is quoted from a randomised controlled trial, and each of those trials was run in people with chronic hepatitis, sepsis, severe pancreatitis, cancer, HIV or dialysis dependence, never in healthy adults taking it for immune support. The calculator here converts a vial size and a mixing volume into mg/ml and U-100 syringe units, which is arithmetic about a vial rather than a dose.
Curated by Dosavy from published literature and regulator labels. Published 11 September 2026, last reviewed 11 September 2026. No clinician reviews this page.
Enter a target dose above to see the draw.
What the evidence says
| Experience | Route | Range | Frequency |
|---|---|---|---|
| Beginner | Subcutaneous | 1.6 mg[1][2][3][4][5]The standard and by far the most replicated regimen: 1.6 mg subcutaneously twice weekly, for 6 months in chronic hepatitis B and C, for 12 weeks to 48 weeks alongside peginterferon in hepatitis C, for 12 months as adjuvant therapy after resection of HBV-related hepatocellular carcinoma, and for 8 weeks as COVID-19 prophylaxis in renal dialysis patients. Several trials express the same dose on a body-surface basis as 900 mcg/m2 twice weekly. This is the regimen a Thymosin Alpha-1 protocol should be understood to mean unless a critical-care setting is being described. | Twice weekly |
| Intermediate | Subcutaneous | 1.6 mg[6][7][8][9]The intensive short course used in critical-care trials, the same 1.6 mg per injection as the standard regimen, but given twice daily for one week instead of twice weekly for months. Used in the TESTS phase 3 sepsis trial (which found NO mortality benefit) and in the multicentre pancreatitis trial, where the 7 days of 12-hourly dosing was followed by 1.6 mg once daily for a further 7 days. This is an inpatient protocol in acutely ill patients, not a schedule anyone escalates to at home. | Every 12 hours for 7 days |
| Advanced | Subcutaneous | 3.2 mg[10][11]The highest per-injection amount that has been given in a published human trial: 3.2 mg twice weekly for 12 weeks in an HIV immune-reconstitution pilot (20 patients), and 3.2 mg twice per day for 7 days in severe acute pancreatitis. 'Advanced' here means 'the highest dose that has been studied', NOT a dose users should progress to: no trial has compared 3.2 mg against 1.6 mg head to head, so there is no evidence that doubling the dose does anything, and the negative TESTS result was obtained at the lower dose. Both 3.2 mg protocols were in patients with serious disease under medical supervision. | Twice weekly (12-week course) or twice daily (7-day course), depending on the trial protocol |
- BeginnerSubcutaneous
Twice weekly
The standard and by far the most replicated regimen: 1.6 mg subcutaneously twice weekly, for 6 months in chronic hepatitis B and C, for 12 weeks to 48 weeks alongside peginterferon in hepatitis C, for 12 months as adjuvant therapy after resection of HBV-related hepatocellular carcinoma, and for 8 weeks as COVID-19 prophylaxis in renal dialysis patients. Several trials express the same dose on a body-surface basis as 900 mcg/m2 twice weekly. This is the regimen a Thymosin Alpha-1 protocol should be understood to mean unless a critical-care setting is being described.
- IntermediateSubcutaneous
Every 12 hours for 7 days
The intensive short course used in critical-care trials, the same 1.6 mg per injection as the standard regimen, but given twice daily for one week instead of twice weekly for months. Used in the TESTS phase 3 sepsis trial (which found NO mortality benefit) and in the multicentre pancreatitis trial, where the 7 days of 12-hourly dosing was followed by 1.6 mg once daily for a further 7 days. This is an inpatient protocol in acutely ill patients, not a schedule anyone escalates to at home.
- AdvancedSubcutaneous
Twice weekly (12-week course) or twice daily (7-day course), depending on the trial protocol
The highest per-injection amount that has been given in a published human trial: 3.2 mg twice weekly for 12 weeks in an HIV immune-reconstitution pilot (20 patients), and 3.2 mg twice per day for 7 days in severe acute pancreatitis. 'Advanced' here means 'the highest dose that has been studied', NOT a dose users should progress to: no trial has compared 3.2 mg against 1.6 mg head to head, so there is no evidence that doubling the dose does anything, and the negative TESTS result was obtained at the lower dose. Both 3.2 mg protocols were in patients with serious disease under medical supervision.
Published ranges, reported as the literature states them and numbered to the sources at the foot of this page. Not a recommendation.
Thymosin Alpha-1 at a glance
- Category
- Other
- Half-life
- 2–3 h
- Routes
- Subcutaneous
- Regulatory status
- Not approved
- Also sold as
- Thymosin alpha 1, Thymosin alpha-1, Ta1, Talpha1, Thymalfasin, Zadaxin
Mechanism
A 28-amino-acid N-terminally acetylated peptide, originally isolated from thymosin fraction 5 (a bovine thymus extract) and now produced synthetically. It is an immune modulator rather than an anabolic or metabolic agent: it influences T-cell production and maturation, stimulates Th1 cytokines such as interferon-gamma and interleukin-2, and activates natural-killer-cell-mediated cytotoxicity. In hepatitis B patients it has been shown to shift T-helper 1 / T-helper 2 cytokine synthesis. It is rapidly absorbed after subcutaneous injection, reaching peak serum concentration within 1-2 hours, with blood levels returning to baseline within 24 hours and a distribution volume consistent with the extracellular space.
Reconstitution
The pharmaceutical product (thymalfasin) is supplied as a powder for injection with its own diluent and is reconstituted immediately before use. Material sold by research-chemical vendors as 'thymosin alpha-1' has no validated reconstitution procedure, potency assay or sterility assurance, and cannot be assumed equivalent to the product used in the trials below.
Storage
No FDA label exists to define storage. In the approved non-US products it is supplied as a powder for injection reconstituted immediately before subcutaneous administration.
Frequency in practice
Subcutaneous injection twice weekly for months in the chronic viral hepatitis and oncology-adjuvant programmes; every 12 hours for 7 days in the critical-care trials.
Regulatory
Not approved by the FDA. Marketed as Zadaxin (thymalfasin, SciClone Pharmaceuticals) and registered as a prescription medicine in a number of countries (principally in Asia, Latin America and parts of Europe) for chronic hepatitis B and C and as an immune adjuvant. Its clinical development programme (hepatitis C phase III, hepatitis B phase II) never produced US approval. In the US it is therefore an unapproved drug, and the material sold online under this name is not the studied pharmaceutical product.
What to know before anything else
Not FDA-approved. Product sold as 'thymosin alpha-1' by research-chemical vendors is not thymalfasin and has no established identity, potency or purity.
The largest trial ever run on this compound was negative and raised a possible harm signal. TESTS (1106 adults with sepsis, phase 3, 22 Chinese centres) found no reduction in 28-day all-cause mortality (23.4% vs 24.1%, HR 0.99). A prespecified subgroup analysis showed a differential effect by age, with a hazard ratio of 1.67 (95% CI 1.04 to 2.67) in participants under 60, that is, a point estimate favouring placebo in younger patients (PMID 39814420).
The phase III placebo-controlled trial in chronic hepatitis B (97 patients) did not confirm the efficacy reported in earlier studies; complete response was 14% on thymosin alpha-1 versus 4% on placebo, P=0.084 (PMID 10607256).
Most of the positive hepatitis results are for thymosin alpha-1 COMBINED with interferon or peginterferon plus ribavirin, not as monotherapy. Taking it alone is not the regimen those trials tested.
It works by augmenting T-cell function. Its effects in autoimmune disease, in transplant recipients on immunosuppression, in pregnancy, and alongside immune checkpoint inhibitors have not been characterised, and no FDA-standard contraindication or interaction list exists.
The populations studied were people with chronic hepatitis, sepsis, severe pancreatitis, cancer, HIV or dialysis dependence. No trial has evaluated it in healthy adults taking it for general 'immune support'.
Thymosin Alpha-1 questions
Is there an established human dose for Thymosin Alpha-1?
Yes, and it is unusually well replicated for a compound with no FDA label. One subcutaneous regimen carries almost the whole programme: a 1999 phase III multicentre randomised placebo-controlled trial in 97 people with chronic hepatitis B, the seven randomised monotherapy studies pooled in a 2004 review, a 2012 multicentre randomised trial in 552 people with hepatitis C on a background of peginterferon alfa-2a and ribavirin, and a 2015 multicentre randomised trial of adjuvant therapy after curative resection of HBV-related hepatocellular carcinoma. Critical care uses a separate short intensive course. Both, plus the highest amount ever given in a trial, are in the published range below with the study beside each one.
Is Thymosin Alpha-1 FDA approved, and what is Zadaxin?
It is not approved by the FDA. Zadaxin is the brand name of thymalfasin, the pharmaceutical form of the same peptide, and it is registered as a prescription medicine in a number of countries, principally in Asia, Latin America and parts of Europe, for chronic hepatitis B and C and as an immune adjuvant. In the United States it is therefore an unapproved drug. The consequence for a reader matters more than the label: the material sold online under this name is not the product those registrations cover, and none of the trial evidence on this page was generated with it.
How does Thymosin Alpha-1 work?
It is a 28-amino-acid N-terminally acetylated peptide, originally isolated from a bovine thymus extract and now made synthetically. It is an immune modulator rather than an anabolic or metabolic agent: it influences T-cell production and maturation, stimulates Th1 cytokines such as interferon-gamma and interleukin-2, and activates natural-killer-cell-mediated cytotoxicity. In hepatitis B patients it has been shown to shift T-helper 1 and T-helper 2 cytokine synthesis. It is rapidly absorbed after subcutaneous injection, peaking in serum within one to two hours, with blood levels back at baseline inside 24 hours and a distribution volume consistent with the extracellular space.
What did the sepsis trial find?
The largest trial ever run on this compound was negative and raised a possible harm signal. TESTS (PMID 39814420), a phase 3 double-blind randomised placebo-controlled trial published in 2025 across 22 Chinese centres, gave subcutaneous thymosin alpha-1 or placebo to 1106 adults with sepsis and found no reduction in 28-day all-cause mortality, 23.4% against 24.1%, hazard ratio 0.99. No secondary or safety outcome differed significantly. A prespecified subgroup analysis showed a differential effect by age, with a hazard ratio of 1.67 (95% CI 1.04 to 2.67) in participants under 60, a point estimate favouring placebo in the younger half of the trial.
Does Thymosin Alpha-1 do anything for general immune support?
Nothing published answers that question. No trial has evaluated it in healthy adults taking it for general immune support; the studied populations were people with chronic hepatitis, sepsis, severe pancreatitis, cancer, HIV or dialysis dependence. Two further limits sit inside the hepatitis literature that is usually cited for it. The 1999 phase III placebo-controlled trial in chronic hepatitis B did not confirm the efficacy reported in earlier studies, with a complete response of 14% against 4% on placebo at P=0.084. And most of the positive hepatitis results are for thymosin alpha-1 combined with interferon or peginterferon plus ribavirin, not taken alone, so monotherapy is not the regimen those trials tested.
Is research-grade thymosin alpha-1 powder the same as thymalfasin?
No. The approved non-US product is a powder for injection supplied with its own diluent and reconstituted immediately before injection. Material sold by research-chemical vendors under this name has no validated reconstitution procedure, no potency assay and no sterility assurance, and cannot be assumed equivalent to what the trials used. No FDA label exists to define its storage either.
Who should be cautious with Thymosin Alpha-1?
It works by augmenting T-cell function, which makes the unstudied situations the ones worth naming. Its effects in autoimmune disease, in transplant recipients on immunosuppression, in pregnancy, and alongside immune checkpoint inhibitors have not been characterised, and with no FDA label there is no FDA-standard contraindication or interaction list for it anywhere. This library holds no reviewed interaction data for it either.
Every number above, and where it came from
11 sources, numbered where they are used. Each one links to the paper or the label itself, not to a summary of it.
- [1]Thymosin alpha1 treatment of chronic hepatitis B: results of a phase III multicentre, randomized, double-blind and placebo-controlled study
Journal of viral hepatitis · 1999 · Randomized controlled trial, phase III, multicentre · n=97
- [2]Thymalfasin for the treatment of chronic hepatitis B
Expert review of anti-infective therapy · 2004 · Review of randomized controlled trials
- [3]Thymosin alpha-1 with peginterferon alfa-2a/ribavirin for chronic hepatitis C not responsive to IFN/ribavirin: an adjuvant role?
Journal of viral hepatitis · 2012 · Randomized controlled trial, multicentre · n=552
- [4]A multicenter, randomized, observation-controlled clinical trial to evaluate the efficacy and safety of thymalfasin adjuvant therapy in patients with HBV-related HCC after curative resection - first announcement of the protocol
Expert opinion on biological therapy · 2015 · Randomized controlled trial, multicentre (protocol)
- [5]A randomized, controlled study of thymosin-alpha1 therapy in patients with anti-HBe, HBV-DNA-positive chronic hepatitis B
Digestive diseases and sciences · 2000 · Randomized controlled trial · n=44
- [6]The efficacy and safety of thymosin α1 for sepsis (TESTS): multicentre, double blinded, randomised, placebo controlled, phase 3 trial
BMJ (Clinical research ed.) · 2025 · Randomized controlled trial, phase 3, multicentre · n=1106
- [7]Immune enhancement in patients with predicted severe acute necrotising pancreatitis: a multicentre double-blind randomised controlled trial
Intensive care medicine · 2022 · Randomized controlled trial, multicentre, double-blind
- [8][Effects of thymosin-alpha1 on cell immunity function in patients with septic shock]
Zhongguo wei zhong bing ji jiu yi xue = Chinese critical care medicine = Zhongguo weizhongbing jijiuyixue · 2007 · Randomized controlled trial
- [9][Effect of continuous blood purification and thymosin alpha1 on the cellular immunity in patients with severe sepsis: a prospective, randomized, controlled clinical trial]
Zhongguo wei zhong bing ji jiu yi xue = Chinese critical care medicine = Zhongguo weizhongbing jijiuyixue · 2009 · Randomized controlled trial
- [10]A pilot study of the safety and efficacy of thymosin alpha 1 in augmenting immune reconstitution in HIV-infected patients with low CD4 counts taking highly active antiretroviral therapy
Clinical and experimental immunology · 2003 · Clinical trial, phase II · n=20
- [11]Thymosin alpha 1 is associated with improved cellular immunity and reduced infection rate in severe acute pancreatitis patients in a double-blind randomized control study
Inflammation · 2011 · Randomized controlled trial, double-blind
The rest of the math
- Reconstitution calculatorThe full version of the tool above, with syringe barrel sizes and IU conversion.
- Vial longevityHow many doses a vial holds and the date it runs out.
- Cost per doseVial price against doses drawn, so two vial sizes can be compared honestly.
- Half-life and decayFirst-order clearance, time to steady state, and what remains at a given hour.
Same class as Thymosin Alpha-1
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