Objectives To assess the temporal change in test use in UK primary care and to identify tests with the greatest increase in use.
Design Retrospective cohort study.
Setting UK primary care.
Participants All patients registered to UK General Practices in the Clinical Practice Research Datalink, 2000/1 to 2015/16.
Main outcome measures Temporal trends in test use, and crude and age and sex standardised rates of total test use and of 44 specific tests.
Results 262 974 099 tests were analysed over 71 436 331 person years. Age and sex adjusted use increased by 8.5% annually (95% confidence interval 7.6% to 9.4%); from 14 869 tests per 10 000 person years in 2000/1 to 49 267 in 2015/16, a 3.3-fold increase. Patients in 2015/16 had on average five tests per year, compared with 1.5 in 2000/1. Test use also increased statistically significantly across all age groups, in both sexes, across all test types (laboratory, imaging, and miscellaneous), and 40 of the 44 tests that were studied specifically.
Conclusion Total test use has increased markedly over time, in both sexes, and across all age groups, test types (laboratory, imaging, and miscellaneous) and for 40 of 44 tests specifically studied. Of the patients who underwent at least one test annually, the proportion who had more than one test increased significantly over time.