Diabetes mellitus type 1, also known as type 1 diabetes, is a form of diabetes mellitus in which not enough insulin is produced. This results in high blood sugar levels in the body. The classical symptoms are frequent urination, increased thirst, increased hunger, and weight loss. Additional symptoms may include blurry vision, feeling tired, and poor healing. Symptoms typically develop over a short period of time. The cause of type 1 diabetes is unknown. However, it is believed to involve a combination of genetic and environmental factors. Risk factors include having a family member with the condition.