You stated that you believe a blood glucose of 140 mg/dl would cause diabetic neuropathy whereas your GP quoted a blood glucose of 150 mg/dl as causative of diabetic neuropathy.
It doesn't seem like things are as starkly different as that. Patients usually develop diabetic neuropathy over many years, so it's not clear that your GP would have 'guaranteed you diabetic neuropathy'.
And yes, I cite 140mg/dL causes neural damage and shows itself as diabetic neuropathy. Proof.
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>Diabetic Retinopathy Develops at "Prediabetic" Blood Sugar Levels
NIH News: Diabetic Retinopathy Occurs in Pre-Diabetes. http://www.nih.gov/news/pr/jun2005/niddk-12.htm
Relation between fasting glucose and retinopathy for diagnosis of diabetes: three population-based cross-sectional studies Wong TY, et al Lancet 2008; 371: 736-743.
Association of A1C and Fasting Plasma Glucose Levels With Diabetic Retinopathy Prevalence in the U.S. Population: Implications for diabetes diagnostic thresholds Yiling J. Cheng et al. Diabetes Care November 2009 vol. 32 no. 11 2027-2032. doi: 10.2337/dc09-0440
Glycemic Thresholds for Diabetes-Specific Retinopathy: Implications for Diagnostic Criteria for Diabetes:The DETECT-2 Collaboration Writing group. Stephen Colagiuri et al. Diabetes Care Published online before print October 26, 2010, doi: 10.2337/dc10-1206
Hemoglobin A1c and Fasting Plasma Glucose Levels as Predictors of Retinopathy at 10 Years: The French DESIR Study. Massin P. et al. Arch Ophthalmol.2011 Feb;129(2):188-195.
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> Beta Cell Destruction Begins at 2-hr OGTT Test Readings Over 100 mg/dl (5.6 mmol/L
Beta-cell dysfunction and glucose intolerance: results from the San Antonio metabolism (SAM) study. Gastaldelli A; Ferrannini E; Miyazaki Y; Matsuda M; De Fronzo RA;Diabetologia 2004 Jan;47(1):31-9)
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>Beta Cells Die Off in People Whose Fasting Blood Sugar is Over 110 mg/dl (6.1 mmol/L)
Beta-cell deficit and increased beta-cell apoptosis in humans with type 2 diabetes. Butler AE, Janson J, Bonner-Weir S, Ritzel R, Rizza RA, Butler PC.Diabetes. 2003;52:102-110.
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>Blood Sugars Over 150 mg/dl (8.3 mmol/L) Kill Transplanted Beta Cells in Mice
ß-Cell Death and Mass in Syngeneically Transplanted Islets Exposed to Short- and Long-Term Hyperglycemia. Montserrat Biarnés, Marta Montolio, Victor Nacher, Mercè Raurell, Joan Soler, and Eduard Montanya. Diabetes 51:66-72, 2002
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>Prolonged Exposure to Blood Sugars Over 140 mg/dl (7.8 mmol/L) Kills Human Beta Cells
Determinants of glucose toxicity and its reversibility in pancreatic islet Beta-cell line, HIT-T15.Catherine E. Gleason, Michael Gonzalez, Jamie S. Harmon, and R. Paul Robertson.Am J Physiol Endocrinol Metab 279: E997-E1002, 2000.
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>One Hour OGTT Result over 155 mg/dl(8.6 mmol/L) Correlates with Markers for Cardiovascular Disease
Inflammation markers and metabolic characteristics of subjects with one-hour plasma glucose levels. Gianluca Bardini et al. Diabetes Care Published online before print November 16, 2009, doi: 10.2337/dc09-134
Edited: added lines for clarity between studies.
Added: I read one of the studies, and it doesn't really controvert your doctors quote. It gives fasting glucose target a lot lower than 140 or 150 (as it should be), and 2hr glucose a lot higher than 150.
In essence, I think you're just interpreting these studies as you will without a proper medical training. My advice is: don't start experimenting with your life based on such weak foundation.