© 2018 The Authors. Diabetic Medicine published by John Wiley & Sons Ltd on behalf of Diabetes UK Aims: Guidelines recommend testing HbA 1c every 3–6 months in people with diabetes. In the United Kingdom (UK), primary care clinics are financially incentivized to monitor HbA 1c at least annually and report proportions of patients meeting targets on 31 March. We explored the hypothesis that this reporting deadline may be associated with over-frequent or delayed HbA 1c testing. Methods: This analysis used HbA 1c results from 100 000 people with diabetes during 2005–2014 in the Clinical Practice Research Datalink UK primary care database. Logistic regression was used to explore whether the four months prior to the deadline for quality reporting (December to March) or individual's previous HbA 1c were aligned with retesting HbA 1c within 60 days or > 1 year from the previous test, and identify other factors associated with the timing of HbA 1c testing. Results: Retesting HbA 1c within 60 days or > 1 year was more common in December to March compared with other months of the year (odds ratio 1.06, 95% confidence interval 1.04–1.08 for retesting within 60 days). Those with higher HbA 1c were more likely to have a repeat test within 60 days and less likely to have a repeat test > 1 year from the previous test. Conclusions: We have found that retesting HbA 1c within 60 days and > 1 year from the previous test was more common in December to March compared with the other months of the year. This work suggests that both practice-centred administrative factors and patient-centred considerations may be influencing diabetes care in the UK.