My dog is sick after stopping steroids. Adrenal glands or upset?

It certainly could be something simple such as an upset tummy so I would try not to over think anything just yet. Try starving him for 24 hours and feeding chicken and rice. With his recent history if you feel that he is dehydrated or going downhill go to the vet sooner rather than later.

Hopefully it is a touch of gastroenteritis completely unrelated to his recent illness, but here is some information for you regarding the adrenal gland. The adrenal gland makes natural steroids, when we give steroid medicine this can suppress the adrenal gland releasing natural steroids. It takes a while for this suppression to happen, but it is certainly possible with prolonged use of higher dose steroids. The dog is okay until the steroid medication stops, then it has a steroid deficiency which leads to fatigue, sickness amongst many signs. The adrenal gland isn't damaged in this case, just suppressed. Nevertheless it can make a dog very ill, it is known as secondary adrenal insufficiency. Usually this is avoided by slowly tapering a dog off steroid medication so the gland starts functioning properly again.

This is certainly something to bear in mind, but I would be more inclined to go down the route of gastroenteritis first. Don't hesitate to go to the vet with Bodie if the vomiting is not settling down. If you feel there is little improvement you can certainly mention adrenal insufficiency. Best of luck!