HCG (human chorionic gonadotropin) is used alongside testosterone replacement therapy to preserve testicular size, maintain intratesticular testosterone, and support fertility by mimicking luteinizing hormone. Common protocols range from 250 to 500 IU two to three times per week, with clinical data showing 500 IU every other day can maintain sperm parameters during TRT. Discussions in this tag cover real dosing experiences, subq vs IM injection, timing around testosterone shots, effects on libido and mood, sourcing after the 2020 biologics reclassification, and how men adjust the balance between testosterone and HCG over time.