Type 1 diabetes mellitus (T1DM) is present in about 5–10% of patients with diabetes mellitus. T1DM can be diagnosed at any age; however, it is most common chronic disease in childhood. The most common age of diagnosis is between 5 and 7 years and or near puberty. The classic symptoms include polyuria, polydipsia, polyphagia, and unexplained weight loss. Clinical examination or approach to T1DM patient begins with detailed history taking followed by complete physical examination supported by laboratory investigations. All patients should be examined thoroughly for general examination. It should include height, weight, body mass index, weight gain or loss, monitoring growth of child, nutritional status, and signs of dehydration. A detailed discussion on physical examination and other common associated conditions has been also provided in this chapter.