General practitioner (GP) shortages and increasing demand for care led to the introduction of nurse practitioners (NPs) to primary care. Many concepts for task sharing among health professionals feature complexity. The aim of this narrative review was to examine how complexity is used as a factor for task allocation between GPs and NPs.

According to the PRISMA statement, PubMed and CINAHL were searched systematically, and eligibility criteria were applied to detect literature concerning GPs and NPs in primary care and complexity in the context of task allocation. Relevant information was extracted, and a narrative analysis was performed.

Thirty-seven studies from seven countries were included, comprising quantitative, qualitative, and mixed methods. Complexity was used to describe patients, their needs, and health professionals’ tasks. The understanding of the use of complexity as a factor for task allocation between NPs and GPs was based on the patient population (specific vs. unspecific), the setting (specific vs. unspecific), the numbers of health professionals involved (two vs. more than two), and the NP role (distinct model of care vs. no model). Despite similarities in these areas, the tasks which NPs perform range from providing minor to complex care. However, there is a slight trend towards NPs treating socially complex patients and GPs focusing on medically complex cases.

Complexity as a concept is prominent in primary care but remains broad and inconsistent as a factor for task allocation between NPs and GPs. This review can be used as a point of reference when practitioners are seeking methods for task allocation in a collaborative primary care setting.