One aspect of diabetic neuropathy stems from a change in the flexibility of the cell wall in erythrocytes (red blood cells). In diabetes, the red blood cell wall becomes "stiff". That prevents the cell from deforming sufficiently to squeeze through the very narrow capillaries at the tips of the fingers and toes. Over time, the causes oxygen starvation to those areas. Nerve damage and numbness shows up first. In time, the oxygen starved tissue dies. Amputation becomes necessary.
I would recommend researching intravenous Vit C before I would do amputation.