Purpose: To evaluate doctors’ adherence to Malaysian Clinical Practice Guideline (CPG) 2009 in established diabetic patients with hypertension, dyslipidemia, renal diseases, obesity, and also to assess factors associated with guideline adherence and diabetes mellitus control in Pulau Pinang Hospital, Malaysia.

Method: Prescriptions written by 24 doctors for 480 established diabetic patients with hypertension, dyslipidemia, renal diseases and obesity (20 patients per doctor) were noted. The control of the disease and CPG adherence were noted from the selected prescriptions.

Results: Three hundred and forty nine (72.7 %) patients received guideline-compliant pharmacotherapy. CPG adherence had statistically non-significant association (p < 0.301) with hypertension, hypertension with dyslipidemia (p < 0.078), dyslipidemia (p < 0.061), renal diseases (p < 0.544) and obesity (p < 0.073). Two hundred and ninety nine (62.3 %) patients were at goal blood glucose level. Diabetes Mellitus (DM) control had statistically significant association (Ф = 0.583, p < 0.001) with guideline compliance and statistically non-significant association (p < 0.066) with co-morbidities and also non-significant association (p < 0.300) with therapies.

Conclusion: Prescribing practices were fairly compliant with guidelines. Doctors poorly adhered to guidelines in diabetic patients with hypertension, dislipidemia, renal diseases and obesity. Significantly better diabetic control was seen in patients who were on monotherapy and guidelines-adherent therapy.