Guidesto Peptides

Is Thymosin Beta-4 safe?

Limited Evidence

Side effects, risks, and safety considerations based on available research.

Research status

Thymosin Beta-4 has very limited human safety data. Most information comes from animal studies, in vitro research, or anecdotal reports. This means the true risk profile in humans is largely unknown.

Known concerns & side effects

  • ⚠no approved human use anywhere — research chemical only
  • ⚠TB-500 and TB-4 are frequently conflated; most products sold as TB-4 are actually the shorter fragment
  • ⚠Phase 2 human trials for cardiac repair (MI) were inconclusive and not advanced to Phase 3
  • ⚠full TB-4 protein significantly more expensive and less stable than TB-500 fragment
  • ⚠no long-term human safety data

Use caution with

no specific known interactions, but combine with caution given absence of human safety dataactive cancer or cancer history — angiogenesis promotion has theoretical oncological concerns

See all 2 studies on the full Thymosin Beta-4 profile.

Frequently asked questions

What is the difference between TB-4 and TB-500?

TB-4 is the full 43-amino acid peptide naturally present in human cells. TB-500 is just the active fragment at positions 17–23 (the LKKTET sequence) responsible for actin-binding and healing properties. TB-500 is cheaper, more chemically stable, and easier to synthesize correctly. Most research on "TB-4" in the wellness community is actually conducted using this shorter fragment.

Did TB-4 advance to Phase 3 clinical trials?

No. RegeneRx conducted Phase 2 trials for dry eye syndrome, venous stasis ulcers, and acute myocardial infarction. Results were either modestly positive or inconclusive — none reached statistical thresholds or commercial viability to advance to Phase 3. Development has not meaningfully progressed beyond Phase 2.

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Last updated: 2026-06-10

Medical Disclaimer

The information on this site is for educational and informational purposes only. It is not intended as medical advice and should not be used to diagnose, treat, or prevent any condition. Always consult with a qualified healthcare professional before starting any new supplement, peptide, or treatment protocol.