Peptides are often well tolerated, but they can still cause temporary reactions while the body adapts. Some commonly reported effects include: BPC 157 headaches, nausea, increased appetite TB 500 4 Dangerous Side Effects of Peptide Injections Can BPC 157 Cause Erectile Dysfunction? Therapeutic Peptides in Aesthetic, Metabolic and Endocrine Conditions: Effects, Safety, Clinical Applications, and Future Perspectives