Guinea pigs are popular companion mammals that are frequently evaluated in veterinary practice, yet they present unique challenges related to their species-specific anatomy, physiology, nutrition, and behavior. This lecture provides a comprehensive, clinically focused approach to guinea pig medicine, integrating foundational principles with practical disease management strategies to improve patient outcomes. Topics will begin with an overview of proper husbandry, anatomy, physiology, manual restraint, and sedation techniques essential for safe handling and examination. Diagnostic sample collection will be emphasized, including practical instruction in phlebotomy, urine collection, and diagnostic imaging, as these techniques are critical for accurate diagnosis and monitoring. Drug therapy, critical care interventions, and supportive care strategies will also be discussed. The lecture will then transition to common medical conditions encountered in guinea pigs, with emphasis on timely recognition, diagnostic evaluation, and evidence-based treatment and prevention. Key disease topics include nutritional disorders such as dietary imbalances and hypovitaminosis C, musculoskeletal conditions including arthritis, fibrous osteodystrophy, and pododermatitis. Common gastrointestinal, urinary, and reproductive disorders will be discussed, including dental disease, cystitis, urolithiasis, and ovarian cysts. Additional sections will address respiratory, dermatologic, neurologic, and endocrine diseases, as well as neoplastic conditions. Throughout the lecture, medical therapy, critical care interventions, supportive care, and husbandry optimization will be highlighted as essential components of successful management. Attendees will ideally gain practical tools to confidently evaluate, diagnose, and treat guinea pig patients in both general and referral practice settings.