I went in once with just hallucinations. I guess in context of the time of my life I had severe depression but wasn't suicidal. The hallucinations were different and my pdoc wanted me to get checked out. (This is where it gets different: my pdoc is the doctor in charge of the residency program at my hospital so when she called a resident and said "this patient is coming in. Do this and this" what she said was done, which may not always be true). But I went in, told them I was hallucinating and was put in a psych ER room, which is just a room with nothing but a stretcher. The doctor checked me out and did a psych eval and said that if it was neurological as suspected I'd be medically admitted to that hospital and if it wasn't then they were going to send me to the hospital's psych facility for observation and treatment of the hallucinations. It turned out that my lithium level was sky high and the hallucinations were neurological so I went to the medical floor. So you can be admitted for hallucinations without ideation but I don't know how often.