Hi and welcome.
It sounds to me very like he needs to change his diet and seriously reduce his carbohydrate consumption (all carbs turn to sugar once in the system). If he does this, he should also lose weight. Weight loss will help enormously, and diet is the key to this. The main carb culprits are cereals, bread (all colours), rice (all colours), pasta (all colours) and potatoes, plus anything made with flour such as pastry and batter. He also needs to be careful with milk and fruits. If he does all this, he has a good chance of bringing his levels back down to single figures, and even much more normal figures.