Type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVDs) often coexist. Oral anticoagulants (OACs) are prescribed for the management of CVDs. However, the safety of OACs in T2DM patients remains unclear. This PhD research aimed to evaluate the use and safety of OACs in T2DM patients. The Health Improvement Network primary care database of the United Kingdom was used to achieve the project aims. Firstly, a systematic review and meta-analysis were conducted to review the literature. Secondly, a drug utilisation study was conducted to evaluate the prescribing of OACs in T2DM. Then, two studies were conducted to explore the epidemiology and treatment of AF in T2DM. Finally, an analytical cohort study using the propensity score and Cox regression models was conducted to investigate the safety of the use of OACs and oral hypoglycaemic agents (OHAs) in T2DM. The pooled average of the prevalence of hypoglycaemia in diabetes was 11.0% (95% confidence intervals, 7.0% – 17.0%). The prevalence of OACs prescribing increased by 50.8% from 4.4% (4.2% – 4.6%) in 2001 to 6.6% (6.5% – 6.7%) in 2015. The prevalence of AF increased from 2.7% (2.5% – 2.8%) in 2001 to 5.0% (4.9% – 5.1%) in 2016. T2DM patients with AF, aged 60-79, males, and BMI ≥25, were more likely to receive OAC. The cohort study results showed that compared with sulfonylurea only, concurrent use of warfarin and sulfonylureas, increased the risk of hypoglycaemia and bleeding, (HR 1.38, (1.10 – 1.75)), (HR 1.12, (1.01 – 1.24)), respectively. However, there was no association between the use of DOACs and sulfonylureas concurrently and the risk of hypoglycaemia, (HR 0.54, (0.27 – 1.10)). In conclusion, the prevalence of AF and the use of OACs in T2DM patients have increased over the last decade. T2DM patients are at a higher risk of developing serious adverse events when warfarin and sulfonylureas are used concurrently
