If I could make a small suggestion, it’s to ask for comprehensive testing, not a c-peptide test. Ideally, you should ask for fasting insulin, fasting BG, A1c, c-peptide, and all available antibody tests (should be 5). I’d even ask for Insulin Tolerance Test, and an oral Glucose Tolerance Test. Why? Because ideally, you want as much information as possible. There are so many profiles for diabetics, it’s really important to understand what is going on. Even for Type 1s and LADA (also Type 1), it’s important to know if insulin resistance is also making life difficult!
C-peptide only measures how much insulin you are producing at a certain point, but if it’s not when you have elevated BG, it won’t actually tell you much. If you aren’t taking exogenous insulin, you can directly measure serum insulin. C-peptide is primarily useful to determine how much insulin is produces endogenously compared to exogenously.
Maybe it’s because I’m a scientist, but I want all the data I can possibly get, and I have doctors that agree with this approach (thankfully). I’m in early-stage LADA and am not using insulin as part of my therapy, but I’ve found all the testing very useful in figuring out what is going on. That is how doctors were able to figure out that I wasn’t a weird Type 2 but had something else going on (first was low insulin in several subsequent tests, and then tested positive for antibodies). It hasn’t resulted in large changes in my treatment, but it does give me good reasons to continue testing and monitoring in a way that most Type 2s would not. Presumably, my beta cells will start to lose the war with my immune system, and I’ll need to use insulin at that point.