I don't think doctors can tell what type of diabetes you have from blood tests...coz they can get it wrong, lots of people here were diagnosed with the other one (to whatever they actually have) for hours, weeks or years. They tend to looks for clues, like how old you are (younger people tend to be assumed to have type 1, although this is often wrong), what kind of build you have (the larger you are the more likely it is you have type 2, although this is sometimes wrong), and whether you have any protein in your urine (yes usually means type 1). They also tend to assume that type 1 is a sudden onset and type 2 is slower in setting in.
I walked into a drop in clinic (coz i work in a hospital anyway) with what i thought was a urinary tract infection which had gotten suffiecently scary that it was messing with my eyesight (my vision had been blurry for a couple of days). They asked for a urine sample and did a glucose test, and then ushered me across to A&E. People asked me how long i'd been diabetic for, and my answer was that i didn't know i was. They assumed at this stage that i was type 1, it seems like the late twenties and early thirties is the one time where nobody expects you to get any type of diabetes, you're too old to be a classic type 1 and too young for a classic type 2. It was only when i came on this site that i realised i wasn't a complete freak of nature, or had the body of a 50 year old. I got a quick intro to insulin injecting and sent home with some pens. The next day i turned up at the diabetes clinic (still in a state of shock) and given some Metformin, that seemed to work and i got rebranded as type 2.
Appologies to everybody who has read that story at least three times now.😉
Rachel