For me, Tegretol has wiped out 90% of my hallucinations because it prevents me from becoming too manic. The way I differentiate is by using my other senses to verify. So for example, while manic and walking in a public park near 10pm, I passed an elderly man whom I thought had a small dark dog following behind him but then running into the bushes to pee. The man did not slow down, which was odd as most people would have waited for their dog to finish their business. However, as I passed him, I turned to yell at him that he was being an irresponsible dog owner. Knowing that a) I was manic and b) my other senses were not confirming a dog's presence - no rustling of leaves with the dog's footsteps, I held my tongue and proceeded to search for the dog. There was no dog.

Another time I had heard some gibberish as if some little being had been sitting on my shoulder. There was no one sitting on my shoulder (visual and auditory messages conflicting = hallucination). Also I had not slept much in the prior 3 weeks.

Now with being medicated, I have mostly olfactory hallucinations and that's a bit harder to verify. Usually it's a very strong foul odor with no obvious cause that just disappears in a matter of seconds/minutes/hours.