Have you had a baseline blood glucose test done? At age 3 and every year after you should have a blood glucose test done on each of your ferrets. This is to make sure they don't have insulinoma.
Mind you, I practice what I preach. At age 3 all three boys got their blood glucose levels tested. Meko already had insulninoma. Koa tested at 90. But Pele, who had no symptoms, tested at 62.
I'm so glad I got them all tested. Otherwise I may have not caught that Pele had insulinoma, which may have resulted in a seizure.
Here are some great places for insulinoma information
http://www.msnusers.com/littlenorway...mabyterri.msnw
http://miamiferret.org/fhc/