We use essential cookies (authentication, your saved goals/stack) by default. With your permission we'll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more about cookies
Prescription medication — not a dietary supplement
Thymosin Alpha-1is a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Most Thymosin Alpha-1 studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 1999–2025 with a typical study size of 316 participants.
Based on 14 studies · 9 meta-analyses · 4 RCTs · 851 total participants
Confidence
HighBy outcome
Thymosin Alpha-1 has an evidence score of 5/10 — moderate evidence based on 14 indexed studies, including 9 meta-analyses. A 28-amino-acid immunomodulating peptide. Unlike most peptides marketed online, this one is a genuine APPROVED DRUG (thymalfasin / Zadaxin) in ~35 countries — though NOT in the US — for chronic hepatitis B/C and as a vaccine adjuvant, and it has real human RCTs and meta-analyses. Honest framing: the best evidence is for hepatitis B/C antiviral response (often as an add-on to interferon/entecavir) and immune restoration in critically ill patients; sepsis and COVID-19 data are mixed (one COVID meta-analysis found benefit, another found none overall). This approved/trial evidence is NOT the same as the 'anti-aging / immune-boost' marketing attached to grey-market injectable vials. Representative study: PMID 21328265.
The commonly studied dose of Thymosin Alpha-1 is Approved-label hepatitis regimen: 1.6 mg subcutaneously twice weekly (thymalfasin/Zadaxin). PRESCRIPTION DRUG abroad — not a self-dosed supplement.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Semaglutide
Mostly mechanism / observationalAn FDA-approved GLP-1 receptor agonist (Ozempic/Rybelsus for type 2 diabetes, Wegovy for chronic weight management) with genuinely strong, large-RCT evidence for glycemic control and substantial weight loss, plus a cardiovascular-outcomes benefit. Honest appraisal: this is a real prescription medicine with real efficacy AND real risks — a boxed warning for thyroid C-cell tumors, pancreatitis and gallbladder risk, very common GI side effects, and growing concern about grey-market/compounded versions. It is included here for reference only, not as a supplement and not auto-recommended.
Last reviewed June 2026 · evidence from 14 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Thymosin Alpha-1 (Thymalfasin)
A 28-amino-acid immunomodulating peptide. Unlike most peptides marketed online, this one is a genuine APPROVED DRUG (thymalfasin / Zadaxin) in ~35 countries — though NOT in the US — for chronic hepatitis B/C and as a vaccine adjuvant, and it has real human RCTs and meta-analyses. Honest framing: the best evidence is for hepatitis B/C antiviral response (often as an add-on to interferon/entecavir) and immune restoration in critically ill patients; sepsis and COVID-19 data are mixed (one COVID meta-analysis found benefit, another found none overall). This approved/trial evidence is NOT the same as the 'anti-aging / immune-boost' marketing attached to grey-market injectable vials.
An approved drug in ~35 countries with real RCTs and meta-analyses supporting hepatitis B/C and immune-restoration use, but sepsis, COVID-19 and cancer evidence is mixed or trend-level only.
Thymosin alpha-1 (Tα1; synthetic name thymalfasin; brand Zadaxin) is a 28-amino-acid peptide originally isolated from thymosin fraction 5, a bovine thymus extract.
It is a true immune-response modifier: in vitro and in vivo it promotes T-cell maturation and differentiation, stimulates Th1 cytokines (interferon-gamma, IL-2), enhances natural-killer-cell cytotoxicity, and acts on dendritic cells largely via Toll-like-receptor signaling (TLR2/TLR9).
Importantly for honest framing, thymalfasin is an APPROVED PRESCRIPTION DRUG in roughly 35 countries (NOT the United States — the FDA has not approved it, and in 2023 it was among peptides the FDA restricted from compounding).
Where it is approved it is used for chronic hepatitis B and C, as a vaccine adjuvant (e.g. influenza, hepatitis B vaccines in poor responders), and it has been studied in severe sepsis, severe acute pancreatitis, AECOPD, certain cancers as an adjuvant, and — during the pandemic — COVID-19.
The human evidence base is real and substantial: multiple randomized controlled trials and systematic reviews/meta-analyses exist.
In chronic hepatitis B, monotherapy RCTs and meta-analyses of interferon-plus-Tα1 or entecavir-plus-Tα1 combinations show improved virological/biochemical response versus monotherapy, with a good tolerability record, though some combination benefits attenuate by 48-52 weeks.
In critical illness, the pivotal multicenter sepsis RCT (ETASS, 361 patients) found only a borderline 28-day mortality benefit (26% vs 35%, RR 0.74) alongside improved monocyte HLA-DR, and the most recent 2025 meta-analysis showed the pooled mortality benefit disappears once you restrict to high-quality and multicenter trials; meta-analyses report restored CD4+ counts and CD4+/CD8+ ratio and reduced extrapancreatic infection in severe acute pancreatitis — but longer-term mortality benefit is less clear.
As a cancer adjuvant a Cochrane review found only non-significant survival trends.
COVID-19 evidence is genuinely mixed: one 2023 meta-analysis found reduced mortality in moderate-to-critical patients, while another 2023 meta-analysis found no overall mortality benefit (only subgroup signals in older/severe patients), so the honest verdict there is uncertain.
Critically, the approved indications (hepatitis, immune adjuvant) and trial evidence are NOT interchangeable with the 'anti-aging,' 'immune-boost,' or general-wellness marketing attached to unregulated grey-market 'thymosin alpha-1' vials sold for research use.
It is injectable (subcutaneous), it is not a dietary supplement, and product quality/identity in the grey market is unverified. The evidence is scored to what the trials show: moderate for hepatitis/immune-restoration use, weaker/mixed for sepsis and COVID-19.
Acts on dendritic cells and monocytes — the leading proposed mechanism is Toll-like-receptor (TLR2/TLR9) signaling (largely preclinical), priming the innate-to-adaptive immune handoff and Th1-skewed cytokine output (IFN-gamma, IL-2).
Promotes maturation and differentiation of T cells and increases thymic output; in critically ill and lymphopenic patients it restores CD4+ counts and the CD4+/CD8+ ratio and can reverse markers of T-cell exhaustion (PD-1, Tim-3).
Enhances natural-killer-cell-mediated cytotoxicity and antiviral immune responses — the rationale for its approved use in chronic viral hepatitis and as a vaccine adjuvant.
How Thymosin Alpha-1 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
Approved-label hepatitis regimen: 1.6 mg subcutaneously twice weekly (thymalfasin/Zadaxin). PRESCRIPTION DRUG abroad — not a self-dosed supplement.
Can be taken without food
| Form | Type |
|---|---|
| 💊Thymalfasin (Zadaxin) subcutaneous injection | Recommended |
The only well-characterized form is the regulated injectable drug product. There is no oral form; 'research use only' vials are unregulated and not interchangeable with the approved drug.
Minimum: 24 weeks
Optimal: 24 weeks
Cycling: Not required
Note: Subcutaneous injection on a fixed schedule (commonly twice weekly for hepatitis). Administered by/under medical supervision where approved.
Dose-response data unavailable. The current published research for Thymosin Alpha-1 does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
RCTs and meta-analyses show higher HBV-DNA clearance, ALT normalization and HBeAg loss when Tα1 is combined with interferon or entecavir versus monotherapy; monotherapy RCTs show sustained response over controls.
Increases CD4+ T cells and CD4+/CD8+ ratio and reduces short-term mortality / infection in sepsis and severe acute pancreatitis meta-analyses — benefit is on immune markers and 28-day outcomes.
One meta-analysis found reduced mortality in moderate-to-critical COVID-19; another found no overall benefit (only subgroup signals). Evidence is genuinely uncertain.
A Cochrane review found thymosin α1 added to chemo/radiotherapy gave only a non-significant trend toward better survival and disease-free survival — not proven benefit. Thymic extracts did cut severe infections during cancer therapy, but most trials were biased.
The approved/trial evidence (hepatitis, immune adjuvant, critical illness) does not validate 'anti-aging' or general 'immune-boost' use in healthy people sold via grey-market vials.
No evidence supports this use in healthy people; the trial evidence is in hepatitis and critically ill patients. Avoid grey-market vials.
Immune-activating — use only under specialist supervision, if at all.
Not established — avoid.
Deliberately combined in hepatitis trials; combination can improve response but interferon's own adverse-event profile dominates — use only under specialist care.
As an immune stimulant, Tα1 could theoretically oppose immunosuppressive therapy (e.g. in transplant recipients). Physician-directed use only.
Tip: Rotate subcutaneous injection sites
Tip: Often reflects the intended immune response in hepatitis; monitored by the treating physician
Tip: Trials consistently report a good tolerability profile; report persistent effects to a clinician
Timing is flexible for Thymosin Alpha-1 — consistent daily use matters more than the time of day. Dosed as a subcutaneous injection on a fixed twice-weekly schedule in hepatitis trials (1.6 mg); acute-care protocols use higher daily dosing.
Thymosin Alpha-1 is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are injection-site reactions (redness, discomfort), transient liver-enzyme (ALT) flare, mild, self-limiting general reactions reported in trials. Use caution if any of these apply to you: Not a US-approved drug or dietary supplement — only use the regulated product where licensed and under medical supervision; Immunosuppressed transplant recipients (theoretical immune-activation risk — physician-directed only); Known hypersensitivity to thymalfasin.
Tirzepatide
Mostly mechanism / observationalAn FDA-approved prescription medication (Mounjaro for type 2 diabetes, Zepbound for obesity and obstructive sleep apnea), not a dietary supplement. Honest appraisal: in head-to-head phase-3 trials it is the most effective approved weight-loss drug to date — up to ~21% body-weight loss over 72 weeks and superior to semaglutide — but it is a real medicine with real risks: a boxed warning for thyroid C-cell tumors, common GI side effects, and pancreatitis/gallbladder signals. Do not source or use it outside a prescription.