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Insulin-dependent diabetes mellitus (IDDM) is a medical term that describes diabetes mellitus that requires insulin therapy to avoid ketoacidosis. IDDM is often considered a synonym for juvenile diabetes mellitus and type 1 diabetes mellitus, though the three terms are not entirely congruent:

• Juvenile diabetes is considered an unsatisfactory and somewhat obsolete term because type 1 diabetes can develop in adults, and type 2 can occur in children.
• IDDM includes type 1 diabetes, but as type 2 diabetes progresses, in some people it may reach a degree of insulin deficiency that requires insulin treatment.

See diabetes mellitus, type 1 diabetes mellitus, and type 2 diabetes mellitus.