TB-500: Side Effects & Safety

TB-500 is a synthetic fragment of naturally occurring thymosin beta-4, which is present in nearly all mammalian cells. Research studies have generally reported a favorable safety profile, with most side effects being mild and transient. However, large-scale human clinical trials have not been completed for TB-500 specifically (its parent molecule thymosin beta-4 has more clinical data).

• Injection site reactions: Mild redness, irritation, or bruising — common with subcutaneous peptide injections
• Headache: Reported in some users, particularly during the loading phase
• Lethargy/fatigue: Temporary tiredness reported in the first few days of use, typically resolving as the body adjusts
• Nausea: Occasional and mild, more common at higher doses
• Head rush/lightheadedness: Transient sensation sometimes reported shortly after injection

• TB-500 promotes cell migration and angiogenesis — theoretical concerns exist regarding use in individuals with active cancer, as these processes could potentially support tumor growth
• Long-term safety studies in humans are limited
• Thymosin beta-4 (the parent molecule) was banned by WADA as a performance-enhancing substance
• Not studied in pregnant or breastfeeding individuals

• Active cancer or history of cancer (due to angiogenic and cell-migration-promoting effects)
• Pregnancy and breastfeeding
• Known hypersensitivity to thymosin peptides

Return to the TB-500 overview for general information.