In type 1 diabetes, the immune system destroys the insulin-producing cells in the pancreas, so people produce little or no insulin and must replace it for life. It often starts in childhood or young adulthood and tends to appear quickly, though adults can develop it too.
In type 2 diabetes, the body becomes resistant to insulin or cannot make enough to keep up. It is more common with age, family history, excess weight, and inactivity, but not everyone with type 2 is overweight. It usually develops gradually and can sometimes be improved with lifestyle changes, alongside medication when needed.
There are other forms too, including gestational diabetes in pregnancy and rarer genetic types. Because management differs significantly, an accurate diagnosis from a doctor matters. Never assume which type you have based on symptoms alone.