C-peptide and GAD antibody tests seem to go hand in hand for accurate diagnosis of T1D. But, because you initially presented with DKA, the doctors will be "certain" that you have T1D because they also go hand in hand as a positive marker of T1D.
There's also genetic testing of sorts for MODY. I don't know (off the top of my head) of any MODY diabetics on the forum to tag here...
This is all very interesting reading. I have recently been diagnosed with T1D (10 weeks!). No DKA but noticed weigh loss, thirst and tested my own BG to find 30 mmol/l! Had some ketones, but highest reading was 2.9. V.long story after this but basically I was diagnosed by the local Diabetes Specialist as T1D 4 days later - my HbA1C was 70. I started having 12 units of long acting and 20g carbs:1 unit rapid acting, however over the following weeks since diagnosis I've arrived at the point where I can't have any rapid and only take 2 units long lasting morning and night, I actually think I don't need any insulin as I'm drifting quite low and may need to stop the long lasting.
The only way for you to be sure you have T1D (which I know from my recent experience) is for you to be tested for the antibodies that your own immune system has created which will/are attacking the beta cells in your pancreas. GAD antibodies are not the only type of antibody that turn on the pancreas, I believe only 85% of T1Ds have the GAD type. It'll be worth having your blood tested for Anti-Islet cell, ZnT8, IA-2 antibodies also, these are common in newly diagnosed T1Ds.
The c peptide test will be interesting to tell you how much function your are getting from you pancreas, but doesn't really tell you you are diabetic, basically gives a good indication of honeymoon status. My c peptide was 1.17 ug/l a few weeks back, this is at the bottom end of the normal range, and I'd expect this reading to be higher since having to reduce my insulin dose to practically nothing.
I know all this and have all this info blood test as I've been getting involved in clinical trials. Not taking experimental drugs, just trying to do my bit to find a cure - unexpected benefit from this has been lots of info and the chance to speak with the top Diabetes experts in the country.
Good look! Enjoy the honeymoon, that's if you really do have them antibodies in there somewhere!
I'm love the honeymoon - 15 mile runs without hypo risk is a luxury I'm going to enjoy for as long as I can!