The prevalence of type 2 diabetes is increasing worldwide, presenting a considerable clinical and public health burden. Existing evidence demonstrates that optimisation of diabetes treatment regimens can reduce the risk of morbidity and disability. This retrospective observational cohort study aimed to identify factors associated with treatment intensification and deintensification in people with type 2 diabetes and evaluate effects of the treatment approaches on clinical outcomes. The cohort included 183 patients enrolled in a primary care Diabetes Medication Therapy Adherence Clinic program in Malaysia between 1 January 2016 and 31 March 2020. Multivariable logistic regression analyses were conducted to determine the clinical or socio-demographic characteristics associated with treatment intensification or deintensification. A total of 175 patients were included in the final analysis. Eighty-seven patients (49.7%) had their medicine regimens changed, of which 27.4% (n = 48) of patients had their medicines intensified, 8.6% (n = 15) of patients had their medicines deintensified, and 13.7% (n = 24) of patients had their medicines intensified and deintensified. In multivariable analyses, treatment intensification was associated with higher knowledge of medicine scores. No factors were significantly associated with treatment deintensification. Patients who had their medicines intensified and deintensified had a lower post followup target glycated haemoglobin level, fasting plasma glucose, and random blood glucose values compared to the baseline. The study found variability in the frequency of intensification or deintensification of diabetes medicine regimens and the factors associated with it. Treatment deintensification was relatively uncommon. To prevent overtreatment, further investigations are warranted to understand the impact of treatment deintensification on patients who were already receiving intensive therapy for type 2 diabetes.