I've never heard of numbers improving that drastically that quickly, but I'm certainly no expert.

I've been low carb for about 8 months now and have seen no improvement in PP numbers with regard to how I process carbs. When I get my annual physical next month, however, I'm hoping my A1C will be even lower showing the effects of my dietary changes.

If you want an accurate test in a controlled environment to see what going on post-prandrial, I'd request an Oral Glucose Tolerance Test from your doc. It's a two hour ordeal at the lab getting stuck four times, but it will really show what's going on. Some researchers recommend that anyone diagnosed with idiopathic SFN should automatically be given this test.

http://www.jabfm.org/content/17/2/127.full

"Conclusion

Based on the data available in the current medical literature, we suggest that patients presenting with unexplained painful sensory neuropathy should be evaluated for impaired glucose metabolism with a 2-hour OGTT; if the results of the test are abnormal, they should be referred for lifestyle interventions and/or initiation of oral hypoglycemic agents in addition to management of neuropathy symptoms. Improved glycemic control can prevent the development of overt diabetes mellitus and may have some impact on progression of neuropathy in these cases. The association between “idiopathic” painful sensory neuropathy and impaired glucose metabolism argues very strongly for prospective studies in larger populations looking at the cost-effectiveness of this approach."