Regional variations in frequency of glycosylated hemoglobin (HbA1c) monitoring in Korea: A multilevel analysis of nationwide data.

•Suboptimal frequency of glycosylated hemoglobin (HbA1c) monitoring is associated with poor diabetes control.•The frequency of HbA1c monitoring is suboptimal in Korea, especially in rural areas.•Policy actions are needed to improve access to testing in rural primary care clinics.