Diabetes mellitus has increased in most countries in the world. Affecting more than 415 million adults in the world. The eleventh most important cause of premature mortality in Egypt is diabetes mellitus. Diabetic patient when admitted to ICU nurses face several challenges that need careful attention. Aim: To assess the complications of diabetic patients in critical care units. Research design: A Descriptive research design was used in the present study. Patients: A convenient sample of critically ill adult patients who were admitted to ICU units (who were150 patient). They were diagnosed as diabetes mellitus or hyperglycemia their ages ranged between (18-60) years from both sex. Setting: ICU units at El-Mabara Hospital & Assiut University hospital include general& trauma &critical intensive care unit. Tools: Tool I: patient assessment sheet. Used to assess the studied patients regard the socio-demographic data and medical related data as base line data Tool II: Diabetes Severity Score (DISSCO). used to assess acute & chronic complication for diabetic patients. Results: complications include (DKA) affected 34% of patients on admission, however (33.3%) at discharge& hyperosmolar hyperglycemic syndrome (HHS) affected 28% of patients on admission, however (26.7%) at discharge. Conclusion: There is significant correlation between the onset of diagnosis and these acute complications. Recommendations: The study Recommends that more research studies to minimize complications of D.M in ICU such as diabetic ketoacidosis, hyperosmolar hyperglycemic syndrome and hypoglycemia.