Question from Leeds, Yorkshire, England:

I have bouts of feeling tired and thirsty for weeks at a time. I periodically get flashes of light in my eyes and have a number of tiny blind spots. Both of my big toes feel somewhat numb–I’m guessing some sort of nerve damage. The thirst does sometimes go away for weeks also. I have been to my GP and had urine tested and fasted and had my blood sugar levels tested twice in the last year, but according to the GP I am not diabetic. I have also been in hospital for 24 hours to check for diabetes insipidus where I fasted and was weighed for a day to see if there was any problem, but nothing was found. Is it possible to have other tests, or could the symptoms be due to something else?