hi kidney failure is very common in diabetic patient if they have poorly controlled diabetes and in my opinion your father is suffering from diabetic nephropathy. it is very difficult to say anything with this much information, i would like to know your father s age, his onset of symptoms and his current renal function tests. once kidneys are damaged it is very difficult to get back complete renal function, what can be done ids to prevent further renal damage by medication and once complete renal failure occurs then there is only renal replacement therapy in the form of dialysis or renal transplant.