Insulinomas are a common problem in middle aged ferrets (3-4 years) and
older ferrets.  With a blood sugar of 45 one can be pretty sure that an
insulinoma is the cause of the hypoglycemia.  No, 45 is not "too low" to
do surgery.  Your description of him still eating well and being active,
etc. are all good signs.  Being just 4 years of age (and assuming he has
no heart problem, etc) means he is a good candiate for surgery.  It does
not make sense to wait untill things get real bad before you do a major
surgery if you can do it when things are still good.  Like most cancer
treatments "the sooner the better" rule applies.  The bad news about
surgery is it usually does not cure the problem.  Most ferrets will
eventually need to be treated medically (diet, pediapred, and proglycem).
 
Hope that helps,
Jerry Murray, DVM
 
[Sukie note: a year for a ferret is like 10 for us, so when insulinoma
surgery adds one or two years to healthy life before further surgery or
meds are used the ferret gains a lot of quality time.]
[Posted in FML issue 3473]