T1 is a condition where the pancreas has stopped making insulin, often as a result of attack by its own immune system. T2 is quite different in origin. The pancreas may be making too much insulin( possibly because of eating too many carbs) and gradually over a long time, the cells become insensitive to it and can't control blood sugars any more. this causes the pancreas to make more and more insulin. Sensitivity gets less and eventually the pancreas gives up from over work. That's a rough, simplified description.T1 most often occurs in young people or children. T2 is more usual in mature adults
T1 always requires insulin therapy to control it. T2 may be controlled by diet and exercise, tablets or insulin therapy,depending on the level of the diabetes.
It's sometimes quite difficult to tell the difference between T1 and T2 when the patient first presents. There is a blood test called the C-peptide test, but it's not definitive. there are some other clues too. T1 usually comes on quite quickly and presents with very high BG numbers. Ketones are usually present in urine. They are a result of the body burning fat instead of sugar and in themselves are not necessarily a bad thing, although they can indicate that bad things may be happening.
It's coming to our notice that doctors often assume that every case of diabetes in an adult is T2. If it is T1, things can get dangerous quite quickly.
Metformin is the offical firstline medication for T2. It doesn't work on T1 and that can be a diagnostic.
I've packed quite a lot into a small space. I hope it's helpful and I expect if I've left something out or made a mistake, someone will pick me up on it