Symptoms of Low Blood Sugar but Normal Labs

My dog has been having the symptoms of hypoglycemia for most of his life, which have started becoming severe lately. He has a serious food aversion from an illness he had as a puppy, so he tends to miss meals and be an extremely picky eater (an issue we are constantly working on). There are times he may go without eating much for nearly 24 hours and when this happens I give when Nutri-Cal or a product called Stat. But, he has started having seizures, which begin with odd behavior if he goes longer than 12 hours without food now. The behaviors are standing & staring at the corner of walls/doors, running crazy, & vomiting yellow-brown foam. His blood sugar tests are normal & all other tests were normal, so what might be causing these low blood sugar-like episodes and seizures?
(We have an appointment with our local vet per instructions of the specialist to get a prescription for Mirtazipine for his appetite).  

[Cliff Redford, DVM]

This is a very tricky case and I am not sure how much help I will be. Chronic hypoglycemia is often due to a hormonal imbalance or for older dogs a tumor attached to the pancreas (insulinoma). But in this case I wonder if your dog has epilepsy and is seizuring/hallucinating (staring at the wall) and the sympotms are being confused with a low blood sugar level. Hypoglycemia can cause seizures however primary epilepsy is more common. The neurologist will be able to help a lot.
Good luck.

[Aharris2006]

Thank you for your response. We have discovered that he has epilepsy and it was probably triggered by the first vaccine he received as a puppy. His brother had a severe reaction to the same vaccine, but my pup's reaction wasn't as noticeable at the time so it went undiagnosed. I'm told it is rather common in some toy breed puppies when they get their first vaccines. We are hoping it will not get any worse, as now he only has seizures a few times a month and the vet wants to take a wait and watch approach for now.