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TB-500 vs Thymosin Alpha-1

Updated 15 sources

Key differences

  1. 1A different peptide altogether. Thymosin alpha-1 is an immune modulator approved in some countries.
  2. 2Different molecules: Ta1 has 28 amino acids and works on immune signalling; TB-500 comes from thymosin beta-4 (43 amino acids) and is used for tissue repair.
  3. 3WADA names thymosin beta-4 and TB-500 under S2; thymosin alpha-1 is not named.
  4. 4Ta1 has an approved product outside the US and large human trials, including a 1,106-patient sepsis trial.

Side by side

Facts from each record, in the same words as their own pages.
TB-500 and Thymosin Alpha-1 side by side
TB-500Thymosin Alpha-1
Category
  • Healing & recovery
  • Immune, Longevity
Evidence
  • Animal data only
  • Some human trials
FDA status
  • Not FDA approvedRegulatory
  • Not FDA approvedRegulatory
WADA
  • Prohibited
  • Not confirmed
Half-life
  • Not established in humans for the fragment. Full-length thymosin beta-4 by IV lasted longer at higher doses; one guide cites 0.5 to 2.1 hours.Clinical study
  • About 2 hours after an injection under the skin, with peak levels at about 2 hours and no build-up between doses (label).Regulatory
  • About 2 to 3 hours per guides; peak 1 to 2 hours after injection.Competitor guide
Routes
  • Subcutaneous injection, Intramuscular injection
  • Subcutaneous injection
Forms
  • Vial (powder)
  • Vial (powder)
Reported doses
  • 1 to 5 mg (subcutaneous injection)
  • 2 to 2.5 mg (intramuscular injection)
  • 500 to 1,000 mcg (subcutaneous injection)
  • 0.8 to 3.2 mg (subcutaneous injection)
  • 40 mcg/kg (subcutaneous injection)
  • 250 to 500 mcg (subcutaneous injection)
Most cited frequency
  • Twice weekly
  • Twice a week
Vial sizes
  • 2 mg, 5 mg, 10 mgCompetitor guide
  • 1.6 mg, 5 mg, 10 mg, 20 mgRegulatory
Mixed vial keeps
  • Fridge at 2 to 8 C, dark, never frozen.Competitor guide
  • Zadaxin mixed with its sterile water is single use: inject immediately.Regulatory
Protocols on file
  • 19
  • 19

Doses shown are what sources report, labelled by origin. Not medical advice.

Read each in full

Sources

15 sources, each checked by date. Record updated Oct 24, 2026. Numbers are restated in our own words and labelled by where they came from.

Regulatory6

  1. WADA 2026 Prohibited ListWADA · checked Oct 24, 2026
  2. Zadaxin injection (SIN07483P) product informationSingapore National Drug Formulary · checked Oct 24, 2026
  3. Zadaxin (thymalfasin) prescribing informationRxList, via a reference work · checked Oct 24, 2026
  4. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A (updated April 22, 2026)FDA (Internet Archive copy) · checked Oct 24, 2026

Competitor guide6

  1. TB-500 profilepathtopeptides.com · checked Oct 23, 2026
  2. Thymosin Alpha-1 profilepeptidesexplorer.com · checked Oct 24, 2026
  3. Thymosin Alpha-1 (TA1) guidepeptidedosingprotocols.com · checked Oct 24, 2026
  4. Thymosin Alpha-1 (10 mg vial) dosage protocolpeptidedosages.com · checked Oct 24, 2026