Goal fasting blood sugar is 80 - 130, post prandial blood sugar is < 180 mg/dl.
Diabetes may not be reversed in all patients with lifestyle changes but it helps to keep it under control and prevent it's complications.
With time, raised blood sugar can damage back of the eye - retina causing Diabetic retinopathy, which left untreated can lead to blindness.
Exact cause is unknown but most appreciated hypothesis is either low insulin or insulin resistance due to genetic +/- environmental factors. Symptoms and signs include increased thirst, extreme hunger, unexplained weight loss, frequent urination, fatigue, irritability, blurred vision, slow healing wounds, presence of ketones in urine, fruity odour and frequent infections.Treatment is either tablets or insulin to control blood sugar levels along with life style modifications (Diet + exercise).