Thank you both
@ert,
@oldgreymare for replying. I am very lucky so far that I am being treated on my clinical presentation and need. I know based on this the underlying diagnosis won’t change much, but I’m one of those people who likes to know!
My HBA1c went from 42 in November to 63 in March so something is definitely amiss!
The GAD result will help confirm whether or not your possible beta cell failure is due to autoimmune factors (indicating LADA, T1) but pragmatically the c peptide test may be more informative about whether you could be in a "honeymoon" state with fluctuating levels of your own insulin. This will help in how to manage going forward.
For example, I was originally diagnosed 12 years ago in Singapore. Presenting with fairly severe symptoms but no DKA. So my then endo put me on insulin and only tested for c peptide and GAD after 3 months and getting my HBAc1 down to 7%. Rationale was that maybe I was T2, but had exhausted my beta cells through insulin resistance. Extra insulin can help them recover. But GAD result was massively positive. At that stage my c peptide was low, but still measurable - in hindsight this meant a diagnosis of LADA, but not a term used there then. But this fit my clinical symptoms as even though I was not particularly well controlled in the first two years, it was only thereafter that I suffered a few episodes of DKA (one life threatening). Nowadays I am extremely sensitive to gaps in my basal insulin.
Fast forward to my last UK endo consult last December with a rather geeky research registrar. He was keen to recommend repeating GAD and c peptide testing as this is not recorded in my NHS results. Just had this done a couple weeks ago. My c peptide test came back effectively 0, down from a low level at original diagnosis. My GAD result is due Thursday - I'll report when I get it.