As CoWriter stated, your father's uncontrolled diabetes is damaging his kidneys. Unless he makes lifestyle changes now he may not have one in the near future. Changes to eating habits, maintaining proper body weight and performing 30 minutes of daily exercise is essential for his well being.
Read other threads on this forum as numerous discussions on what to eat and what not to eat has been discussed numerous times. He can also help his kidneys by drinking 800-1000 ml of water daily, no colored liquids [tea, coffee, soda, etc].
High serum urea means that the diabetes is damaging his kidneys. A blood sugar of 271 is very high. That's what you need to work on, lowering the blood sugar. It will help his kidneys and that may bring the serum urea down.
It's important that he controls his blood sugar because it can cause many other problems besides kidney damage.
Co