Hi acacia
My Dr would not give me the c-peptide test. He said it was pretty obvious I was still making some insulin, and that over time this would reduce, thus the test was not worthwhile.... Which I actually sort of agree with. Your mum is clearly producing some insulin, otherwise she would need insulin injections.
If your mums carb intake is around 50g then going down to Dr Bernstein's recommended 36g per day will likely bring her pre breakfast readings down. Mine went from 6.5s (with 50g carbs) to under 5.0.
I can't consistently get down to Dr B's pre breakfast 4.6s. I think it all depends on how many beta cells we have remaining. The more that have died off, the less likely we can get down to Dr B's recommendations without insulin. I am very happy with my pre breakfast readings of around 5.0, I have kept then in this range for nearly 6 months now, hopefully I can keep them in this range for a few more months.
When my pre breakfast levels hit 7.0 I will be wanting insulin, to get them down.... Indeed I have requested a half unit insulin pen so that I can start even earlier, at around 6.0. My DSN says one unit of insulin will bring my BG levels down around 3.0mmol, which is why I have requested a half unit pen....... I am not ready for it yet, just want it to be prepared. I have had a one unit insulin for 9 months now, not used it yet. Came close when I have a sickness virus, BG levels rise when ill, but luckily they came straight back down again within a few days.
When your mum reads Dr Bernstein book, my guess is, she will either take it on board enthusiastically or decide that it's not for her..... Either way I think she will find it interesting. His methods are definitely not for all, and many don't agree with them. But I have yet to find / read of any other method that clearly works any better, and more importantly, I am finding that his solution works for me.
Like Lucy, I will still follow his solution when I am on insulin, indeed I can see even more benefits of following his solution when on insulin, primarily to keep the risk of hypos to a minimum.... And to keep the risk of complications to a minimum