Glutamic Acid Decarboxylase (GAD) 2000.0 KU/l (Ref Range 0.0 - 5.0 KU/I), what does it mean?

I am a type 1 for the past 10 months and didn’t do this test until last month, just got the results back and the number is kinda scary ! Can anyone tell me is that a normal figure for a type 1 ? Thanks