Hello all,
Really interesting question.
Generally, I agree with
@Brunneria -- we shouldn't overly generalize as T2 seems to be a bit of a catch-all category unless there is testing to specifically determine type. As we all know this really doesn't happe often enough. Instead type is usually guessed at based on age (and often weight). But even assuming that diagnosis is correct and we are truly T2, there still seems to be a lot of interindividual variation.
This having been said, for many of us T2s (maybe even most), producing too much insulin in response to a carb-heavy life style (probably due to a genetic predisosition) seems to be common at least initially.
There are a couple of interesting sources that may support this assumption:
This is an figure from a presentation (red line for average c-peptide levels for low HbA1cs included by me) by Ken Sikaris, a clinical biochemist from the University of Melbourne:
As seen in this graph, average c-peptide levels for elevated HbA1cs seem to be higher than for normal HbA1cs (though more pronounced in the prediabetic range). Average c-peptide levels are still higher for very high HbA1cs in the range of 12% or 108 mmol. Furthermore, it appears that for elevated HbA1cs at least 2/3 of the results are higher than the average for a low HbA1c. I believe this also should be seen in the light of who is likely to be tested for c-peptide -- in my mind this is probably in many cases to be a person suspected of having T1 or LADA. So, in fact this graph would probably be a conservative estimate of the c-peptide production for a T2s (meaning after taking out T1 or LADAs , the average c-peptide production will very likely be higher).
In another article, also found tables comparing characteristics for T1, LADA and T2. Here, insulin production seems to be one of the distinguishing characteristics (
https://www.e-enm.org/journal/view.php?doi=10.3803/enm.2018.33.2.147)
Here is also an article, which looks at what happens to insulin production in T2s over time (
https://pubmed.ncbi.nlm.nih.gov/16939949/). The authors conclude that insulin production often declines for T2s with time, but that this is not inevitable.