Loneliness is a painful experience for patients. To clarity the concept of patient loneliness, this study undertook an evolutionary concept analysis based on a literature search in the main relevant databases. We identified 7 dimensions in adult patients' experiences of loneliness. These dimensions of loneliness have different causes and theoretical foundations, which have different implications for patient care. Patients may be lonely in their different relationships, including those with nurses and doctors. Loneliness in relation to health care professionals is a new application of the concept of loneliness that provides a useful starting point for future research.