Introduction: Diabetes mellitus (DM) is a chronic disease that is prevalent in many countries. The prevalence of DM is on the rise, and its complications pose a heavy burden on the healthcare systems and on the patients’ quality of life worldwide. Materials and Methods: This is a multicentre, cross-sectional study involving 5 Health Clinics conducted by Family Medicine Specialists in Malaysia. Convenience sampling of 100 respondents with DM were selected. The International Classification of Functioning, Disability and Health (ICF) based measures were collected using the Comprehensive Core Set for DM. SF-36 and self-administered forms and comorbidity questionnaire (SCQ) were also used. Results: Ninety-seven percent had Type 2 DM and 3% had Type 1 DM. The mean period of having DM was 6 years. Body functions related to physical health including exercise tolerance (b455), general physical endurance (b4550), aerobic capacity (b4551) and fatiguability (b4552) were the most affected. For body structures, the structure of pancreas (s550) was the most affected. In the ICF component of activities and participation, limitation in sports (d9201) was the highest most affected followed by driving (d475), intimate relationships (d770), handling stress and other psychological demands (d240) and moving around (d455). Only 7% (e355 and e450) in the environmental category were documented as being a relevant factor by more than 90% of the patients. Conclusion: The content validity of the comprehensive ICF Core set DM for Malaysian population were identified and the results show that physical and mental functioning were impaired in contrast to what the respondents perceived as leading healthy lifestyles. Key words: Disability, Functioning, Health, Linear Models