To obtain nationwide data on the incidence and prevalence of diabetes mellitus (DM) in Taiwan, we performed an analysis of the 2000 to 2009 claim data from the National Health Insurance (NHI). One-third of the claims in the NHI database from 2000 to 2009 were randomly sampled. DM was defined by 3 or more outpatient visits with diagnostic codes (ICD-9-CM: 250 or A code: A181) within 1 year or by 1 inpatient discharge diagnosis of DM. In accordance with the global trend for DM, with a near constant standardized incidence rate, there was a more than 70% increase in the total diabetic population, or a 35% increase in the standardized prevalence rate, in Taiwan from 2000 to 2009. The incidence of diabetes was higher in men, especially in the 20 to 59 year-old age group, and the total number of men with diabetes exceeded the number of women in 2005. However, the prevalence and incidence rates in women over the age of 60 years were higher than those in men. According to the strict criteria of the catastrophic illness certificates, type 1 DM was present in less than 1% of the diabetic population in Taiwan. The incidence of type 1 DM remained stable from 2000 to 2009.

　　With our nationwide database, subgroup analysis of DM incidence can be performed to refine our health policies for the prevention, screening, and treatment of diabetes mellitus.