Background: According to World Health Organization (WHO) in 2012, an estimated 1.5 million deaths were a direct outcome to diabetes and another 2.2 million deaths were attributively related to high blood glucose in a global population. As a consequence, researches confirmed that diabetics have a shorter life expectancy than non-diabetic individuals and this extravagant mortality is predominantly due to diabetic complications. Methods: We have conducted a descriptive cross-sectional study on Makkah Region population, Saudi Arabia. All Saudi patients diagnosed with DM, regardless the type, and living in Makkah regions were included in this study. The total sample obtained was 299 patients. A self-administered questionnaire, about knowledge of diabetes mellitus complications, was filled by participants. Results: Participants were classified into five categories according to age. Male and female groups percent was (39.1%) and (60.9%) respectively. Nearly two thirds of participants have the disease for more than five years (63.2%), and nearly two thirds were compliant to their medications (62.5%). Three quarters of participants (76.9%) had positive family history of diabetes mellitus. (26.1%) of participants had only one family member with diabetes mellitus, (16.7%) had two members, and (14.7%) had five members or more with diabetes mellitus.Conclusion: To develop effective patient education and improve patients' diabetic control and own complications, educational strategies are needed so as they may help diabetic patients to improve self-knowledge and recognition of early signs and symptoms of DM complications, and this will prevent further deterioration, which will improve life quality and increase life expectancy for those patients.