If he is getting to the point of having seizures, then you must have the vet adjust meds IMMEDIATELY. Seizures are caused by the insulin attacking the brain when it cannot find enough glucose in the blood. This will cause brain damage, among other things, and when severe enough can cause a terrible death. Prednisolone and Diazoxide together are most effective. Eventually, even they will not be enough. Insulinoma is a terrible disease that can't be cured, only managed or slowed down for a time, and that time varies greatly from ferret to ferret. Good luck. Jeff and Neo [Posted in FML 5493]