I am not sure if your vet has not explained the problem well or if you
have not understood what he said.

Insulinoma does not require a bone marrow test and would not normally
cause anemia. If she is anemic this is another matter but not
insulinoma..

See link below (Bruce Williams site) and print it out for your vet.
(http://www.afip.org/ferrets/PDF/insulinoma.pdf)

Extract...

Definitive diagnosis of insulinoma is made in the vast majority of
cases by a blood glucose test -- rapid, cost-effective, and gloriously
simple. In cases in which the glucose level is less than 60 g/dl
(normal in the ferret is 80-120 g/dl), the presence of an insulinoma is
assured (even without corroborative evidence of clinical signs. If the
blood glucose reading is between 60 and 80 g/dl, concomitant clinical
signs of hypoglycemia are required to make the diagnosis. In cases
in which the glucose level exceeds 80 mg, other forms of neurologic
diseases should be investigated as well. Remember that insulin
secretion in some tumors is sporadic, and normoglycemia one day may
become hypoglycemia the next.

End extract

Tony (not a vet), Sugar and Suki.
In memory of Sally and  Sue

[Posted in FML 5841]