Purpose – The purposes of this paper were to assess the quality of life (QoL) in patients with type II diabetes mellitus (DM) in a suburban tertiary hospital and determine the factors that affect the QoL including individual characteristics, health factors, self-care behaviors and social support.

Design/methodology/approach – This study was a cross-sectional study among DM type II cases being treated in a suburban tertiary hospital in Thailand. Data were collected by personal interview from 188 patients in 2018. Diabetes-39 was administered to assess QoL.

Findings – 54.3 percent of patients had good QoL. Total score of QoL was moderate which found an average score of 216.0 ± 41.0, 46.8% had moderate level in self-care behaviors and 56.4 percent had moderate level in social support. The factors associated with QoL in patients were cerebrovascular disease (Fisher = 7.2, p = 0.01), self-care behaviors (rs = 0.191, p = 0.008) and social support (rs = 0.229, p = 0.002).

Originality/value – Health care system ought to develop a policy driven to improve the QoL in DM type II patients by encouraging self-care behaviors and social support for DM type II patients.