Diabetes mellitus refers to a metabolic disorder characterized by high blood sugar levels due to impaired insulin secretion, insulin resistance, or both. There are various synonyms for diabetes mellitus, including type 1 diabetes, type 2 diabetes, hyperglycemia, and high blood sugar. Type 1 diabetes is an autoimmune condition where the body attacks and destroys insulin-producing cells, leading to insulin deficiency. Type 2 diabetes is a chronic condition that is caused by insulin resistance, where the body becomes less sensitive to insulin, resulting in high blood sugar levels. Hyperglycemia refers to abnormally high blood sugar levels, which can occur in people with diabetes mellitus and other conditions. High blood sugar is a common symptom of diabetes mellitus.