Diabetes mellitus (DM) represents a huge public health problem. According to available date, there is more than 400 000 people in Croatia who are suffering from DM, or every tenth person. DM is a cause of premature death of 5 milion patients in the world, and it is in Croatia on seventh place in the ranking of leading causes of death, with upward trend in the last few decades. Diabetes mellitus type I is a type of disease when body doesn't produce insulin at all, because cells of pancreas that are in charge for producing insulin are completely destroyed. A nurse who works with patients should be educated to conduct health education, but also to recognize potential complications of patients. In the life of patient nurse has a huge importance,because she conducts education of patient and his family, especially if it comes to a child or a person with a cognitive impairments. Education is a process that begins during the first hospitalization when the disease is detected and then it continues through regular check-ups. An important goal of health education of this disease is early and as good as possible emotionally adjustment and acceptance of newly discovered disease by the whole family. Objectives in the work of nurses with patient with DM are: 1. achieving a better general medical health of patient 2. prevention of complication of disease 3. achieving and maintaining ideal body weight 9) achieving and maintaining GUK levels as close to the normal values. There are many nursing diagnosis that may occur by patient who has a DM, but the most often are: • Noncompliance with medical treatment recommendations r/t not accepting disease; • Unbalanced diet r/t a lack of will; Tiredness r/t a basic disease; • Fear r/t the newly discovered disease, lifestyle changes and taking insulin; • Helplessness r/t the newly discovered disease; • High risk of damage to the integrity of the skin r/t a basic disease and the application of insulin therapy; • HR for infection r/t the application of insulin therapy and the implementation of self control of GUK; • Lack of knowledge r/t a lifestyle, therapy, nutrition and a basic disease. However, patients have possibility to get some nursing-medical diagnosis like: • HR for hypoglycemia r/t the use of insulin therapy, increased physical activity, skipping meals lack of knowledge ; • HR for hyperglycemia r/t a skipping of taking insulin therapy, unbalanced diet, lack of knowledge. The nurse should choose the appropriate way of conducting education and recognize strengths of patient so she can help him build up his potential in self-care. It is also important to recognize weaknesses of patient, so the nurse can include social support of the patient who will help him in self-control disease. Diabetes mellitus is a lifetime disease and it requires a lifestyle change, so we can conclude that patient can live normally and have control over his life by carefully planning his everyday activities and by right education. Otherwise, the disease is one that will take control.