Background Test result communication is important for patient-centred care, patient safety and primary care workload. Evidence is needed to ensure that test results are communicated safely and efficiently to patients in primary care. Aim To summarize existing evidence for blood test result communication between primary care providers and their patients and carers. Design and setting Mixed-methods systematic review Methods Medline, Embase, PsycINFO (Ovid); CINAHL (ESCOHost); and the Cochrane Library were searched from 2013 to September 2023. Primary studies of any design that provided information on the communication of blood test results by primary care staff to adult patients and carers were eligible for inclusion. Results There were 71 included studies, including 10 experimental studies and no randomized controlled trials. Study quality was mostly poor and risk of bias was high, partly due to a lack of reported information. Patients want more information about their blood test results, particularly in terms of 'what next', and prefer results to be provided quickly. Electronic methods such as online access or text messages were generally well accepted but not by everyone, and not for all results. Clinicians' opinions were mixed as to whether more information and direct release of test results to patients without clinician input was beneficial or could cause problems, such as increased workload. Conclusions We have identified a range of evidence on patient and clinician preferences, barriers and facilitators to test communication, which is particularly important in the current NHS context of a move towards patient online access.