Although I am not a diabetic, my son is a type 1 diabetic. But this insatiable thirst you speak of, I used to have. And I found the cure. Apparently I was unable to hold on to the water hydrating my cells and I urinated quite frequently. The water just ran through me. Just to give you a general idea of how thirsty I was. I NEVER left the house without water, I was so thirsty I would panic if I had no water as if i was about to die. Maybe so actually. Upon reading a book to rid myself of cellulite, called The Cellulite Solution by Dr Howard Murad. His cure for cellulite also gave a nice side effect. NO being thirsty anymore. Now it does take 2 months for it to work. I also got rid of cracked heels following this. I took Glucosamine Choindroitin and Lecithin. That is all. Now I tested this theory. Once I was cured of cracked heels and thirst. I quit taking these products. Months went by and I was fine. And then the thirst and cracked heels returned. So I guess it's all about maintenance. Sucks but you gotta do it always it seems. But tell him to try that., that might be his problem