Thymosin Beta-4: Side Effects & Safety

Thymosin beta-4 has the most clinical safety data among the thymosin-family peptides, with multiple clinical trials completed for corneal healing, wound repair, and cardiac applications. Overall, it has demonstrated a favorable safety profile with mild and transient adverse effects.

• Injection site reactions: Mild redness, swelling, or bruising — the most commonly reported adverse event in clinical trials
• Fatigue: Transient tiredness reported in some study participants
• Headache: Occasional, typically mild
• Eye irritation: In ophthalmic (eye drop) formulations — mild stinging or tearing

• Oncology considerations: Thymosin beta-4 promotes cell migration, angiogenesis, and tissue growth — properties that raise theoretical concerns in individuals with active cancer. However, some research suggests thymosin beta-4 may actually have anti-tumor properties in certain contexts
• Banned by WADA as a performance-enhancing substance in competitive sports
• Not studied in pregnant or breastfeeding individuals
• Long-term effects of sustained exogenous administration are not fully characterized

• Active cancer (theoretical concern due to pro-angiogenic and cell-migration properties)
• Competitive athletes subject to WADA testing
• Pregnancy and breastfeeding

Return to the thymosin beta-4 overview for general information.