What is the difference between type 1 and type 2 diabetes?

Type 1 is autoimmune destruction of insulin-producing cells, so the body makes little or no insulin — it requires insulin from diagnosis, typically presents younger though not exclusively, and is not caused by diet or lifestyle. Type 2 involves insulin resistance with progressive decline in insulin production, is strongly associated with genetics and lifestyle factors, and is managed with lifestyle, oral medication and sometimes insulin later. The distinction matters clinically because treatment differs entirely, and socially because type 1 patients frequently face inappropriate blame. Adult-onset type 1 exists and is sometimes misdiagnosed as type 2 initially.