Type 2 diabetes mellitus (T2DM) is one of the major diseases threatening the health of Chinese residents. Insufficient glycemic control results in inevitable and sometimes irreversible complications. The condition can be more complicated for patients with comorbidities. To maintain appropriate glycemic control, patients may need to add or switch to different classes of drugs as the disease progresses. The complicated drug treatment for diabetes poses a high risk for drug-drug interactions and challenges patient compliance, which is the most important factor affecting the ability to achieve glycemic control. In addition, T2DM is a life-long disease that is associated with a heavy economic burden for patients’ families and for society. Therefore, this paper aims to characterize the complexity of prescribed medications used to treat T2DM and to assess the trends in the number of complications, medications used, and costs incurred among these patients.

Data were retrieved from two tertiary hospitals. The population consisted of patients receiving at least one diagnosis of diabetes (International Classification of Diseases-10 codes: E11, E12, E13, and E14) between October 2007 and May 2017. Three measures were assessed, including the number of patients with different complications, concomitant drug use, and costs. Patients with a short disease duration (< 5 years) were compared with patients who had a longer disease duration (≥ 5 years).

Of 31,071 patients, about half of those with a longer disease duration had at least five concomitant diseases, compared with nine percent of patients with a shorter disease duration. The maximum number of concomitant diseases was nine for both disease duration groups. Patients with longer disease duration were more likely to use multiple classes of drugs, compared with patients in the short disease duration group. The average annual medical costs for patients without concomitant disease was CNY 1,894 (USD 265).

Overall, the results demonstrated that T2DM is a relatively complex disease. Firstly, patients have up to nine concomitant diseases and use twenty-two classes of drugs. Secondly, patients with more complications tended to use more medications. Thirdly, patients with a longer disease duration tend to have a higher number of concomitant diseases, use more classes of drugs, and have higher medical costs than patients with a shorter disease duration.