Nerve damage can cause symptoms in the voluntary nervous system and in the involuntary, or autonomic, nervous system. The precise mechanism of nerve dysfunction is unclear. The brain and nerve tissue constantly need glucose, or blood sugar, as their source of energy. To ensure continuous energy intake, sugar is transported to nerve cells without insulin, unlike, for example, muscle cells. This is why elevated blood sugar is directly reflected in increased sugar concentration in nerve cells.
When excess sugar accumulates in nerve cells, normal metabolism in the nerve cell becomes burdened. This leads to the accumulation of harmful metabolic products inside the nerve cells. Additionally, elevated blood sugar damages the nerve's own capillaries.
In addition to elevated blood sugar, risk factors for nerve damage include a long duration of diabetes, elevated blood pressure, lipid disorders, smoking, and excessive alcohol use.