Glycated haemoglobin (HbA1c) might reflect glycaemic control in persons with diabetes. Study aims were to identify changes in glycated haemoglobin values and predictors (baseline coping behaviour, fasting plasma glucose, disease-related and demographic factors) in patients during 1 year after hospital discharge. A longitudinal prospective design with convenience sampling was used. Subjects were recruited from a community hospital in Taiwan. Measures included Jalowiec Coping Scale, fasting plasma glucose, HbA1c values, and demographics. Generalized estimating equation was used to determine factors of change in glycated haemoglobin. A total of 57 patients completed 1 year of follow-up. Half did not receive diabetes mellitus education and regular exercise. Patients’ glycated haemoglobin levels follow controls at 6 months after discharge. Patients with higher levels of blood glucose, less problem-focused coping and greater emotion-focused coping were associated with poor glycaemic control. Education programmes should involve individual-centred care and health behaviours for prevention of diabetes complications.