What are the side effects of peptide therapies?

Peptide side effects vary by specific compound but commonly include: injection site reactions (pain, redness, bruising), nausea and gastrointestinal discomfort (particularly with GLP-1s and some growth hormone peptides), headache, fatigue or paradoxical insomnia (depending on peptide and timing), water retention and joint pain (with growth hormone-related peptides), flushing or warmth sensations, and changes in blood sugar or blood pressure. Rare but serious risks include: immune reactions or allergic responses, antibody formation reducing efficacy, organ stress with high doses or prolonged use, and unknown long-term effects since many peptides lack long-term human safety data. GLP-1 medications have the most documented side effect profiles due to extensive clinical trials. Research peptides have less defined risk profiles. Quality concerns compound risks - contaminated or incorrectly dosed products from unreliable sources increase adverse event potential. Any peptide therapy should include baseline health assessments, ongoing monitoring, and immediate cessation if significant side effects occur.