Hi,
I'm sorry to hear you're having similar difficulties to me. You certainly did well to get your HbA1c down to 38 but it's hard to know why that happened unless you were carrying some deep-seated visceral fat which the low carb diet addressed. In my own case, I have seen no improvement at all, 47 at the last test in May but am due to have another next month. I use a finger prick monitor before and 2 hrs after all meals (expensive as a non-diabetic but worth it to keep tabs on the levels) and am pretty sure the next HbA1c will not show an improvement. I had an MRI scan as part of a trial last year and it showed very low visceral fat and the doctor told me that I am not, therefore, insulin-resistant. My BMI is 18.1. I started on 500g metformin in February but it had no effect so the dose was doubled in May. It looks as if it is still not having an effect so I'll need to discuss this with the doc soon. I do a lot of exercise, and, having read that resistance exercises help to reduce glucose levels, now go to the gym 3 times a week for both machine weights and cardio work, as well as walking and doing 3 classes of Pilates a week. I haven't noticed that this helps at all with BG levels but it does make you strong and fit and more likely to cope with health problems so it might be worth looking into that to see if it influences your levels better than mine. You might find that, if you take a 15 minute brisk walk 30 minutes after a meal, it reduces blood sugar spikes but you'd need to be testing to know for sure.
I have done enough research into 'lean diabetes' to virtually be able to write a Ph.D thesis on the subject! It is starting to be recognised as a phenotype in its own right but research is sparse, obviously because there are so many T2 diabetics who need to change their lifestyle and lose weight so that's where the interest and the research money is going. I'm fed up with hearing that all you have to do to reverse T2 is to exercise and lose weight - a very simplistic solution, even though it works for a lot of people who need to make those changes. It does seem though, that our problems could be caused by either malfunctioning or diminishing beta cells, possibly with a genetic connection. Research is currently being done at Leeds Uni into targeting beta cells in lean T2 diabetes (Google it) so it might be worth watching for the results of that in due course. Sorry I can't shed more light on the issue but I'd be interested to hear how you get on!