The Hajj, a mass-gathering of over 3.5-million pilgrims, faces challenges to global health-security, housing, food, water, transportation, communication, sanitation, crowd-control and security. The Indian Medical Mission extended health-security to approximately 140,000 pilgrims, through outreach medical teams, primary-care clinics, tent-clinics, secondary-care hospitals and evacuation capabilities. Data on medical attendance, bed-occupancy, investigations, referrals, medication usage and deaths was compared. Outpatient attendance was 374,475 in static-clinics, 5135 in tent-clinics and 13,473 through task-forces. 585 (62.90%) in-patients were hospitalized amongst 930 secondary-care referrals. Secondary-care bed-days were 2106 with average bed-occupancy being 77.78%. 495 patients were institutionalized in tertiary-care Saudi-Arabian hospitals. Infectious diseases were most commonly (53.26%) encountered due to overwhelming respiratory-infections, followed by trauma (24.40%). Analgesics (66.38/100 patients) and antibacterials (48.34/100 patients) were frequently prescribed. Crude mortality amongst Indian pilgrims was 11.99/10,000. Risk-factors associated with high morbidity were old-age and pre-existing comorbidities. Overwhelming surge of patients facilitates transmission of communicable infections and leads to stress induced physical, mental and compassion fatigue amongst healthcare personnel. Respiratory infections are highly prevalent and easily transmissible during Hajj leading to significant morbidity, increased burden to existing health facilities, overwhelming costs on health systems and globalization of multiresistant pathogens. Diabetic patients should avoid heat exposure and use protective footwear during Hajj rituals. Mass-gathering medicine at Hajj can be optimized by improving patient knowledge on performing Hajj at a younger age, medicine compliance, avoiding self-medication, self-monitoring of hypertension, blood glucose, and preventive health measures; screening of pre-existing comorbidities; and resource augmentation with telemedicine networks and decision-support systems.