Heat waves are becoming more frequent in France, raising concerns about their public health impacts. Existing studies highlight the role of temperature and individual risk factors in heat-related morbidity that generally focus on large cities such as Paris, but overlook nonfatal consequences and other areas. Using healthcare service areas (Territoire de Vie Santé, TVS) as a spatial unit, we examine how exposure, sensitivity, and adaptive capacity shape vulnerability to extreme heat. Our results show that high temperatures and social isolation significantly increase hospital admissions and emergency visits, while wealth and vegetation mitigate health risks. In contrast, age, deprivation, and education do not significantly influence vulnerability, suggesting that economic resources are more critical for adaptation than traditional social risk factors. These findings challenge assumptions about the primary drivers of heat vulnerability and highlight the importance of targeted policies—such as strengthening support networks for isolated individuals—to reduce heat-related health risks in a warming climate.