Hi. The diagnosis of Late onset T1 versus T2 is a walk into the unknown. I was diagnosed as T2 and still am but am confident I'm actualy Late onset T1. In my case and many others you present at diagnosis as slim and having lost weight unexpectedly just prior to diagnosis. You then find that any tablets prescribed work for a while and then fail. You then end up on insulin when blood sugar continues to creep up. I gave up on my diabetes GPs and had a GAD and c-peptide done privately after 7 years. The GAD was negative but the c-peptide showed very low insulin which I had expected. There are two interpretations of the negative GAD. The first is that Late onset T1 can be caused by viruses, pancreatitis and so on; not just GAD antibodies. Second is that according to the 2015 NICE T1 Guidelines document, the GAD test becomes more unreliable as the years pass after diagnosis whereas the c-peptide becomes more reliable. So, if you are slim and tablets no longer work then Late onset T1 is likely. If you have excess weight and haven't yet gone thru three'ish tablet types then T2 remains possible. See how things go and if the HBa1C despite low-carbing goes up above 8% as mine did you know you need insulin.