Any patient presenting with an acute changes in mental state (e.g. changes in speech, behaviour, mood or thought) should be carefully evaluated for physical/organic illness (even with a prior history of mental/psychiatric illness)
You should not presume the deterioration is solely due to mental illness
On occasions it will be safer treating these conditions on a medical ward than a psychiatric ward
The evaluation should include:
Treatable acute organic conditions contributing to the mental state (see Organic versus Functional causes of mental illness)
Life-threatening or other acute co-existing medical conditions
It should be noted that the patient may have a chronic medical condition contributing to their mental state which is not immediately identifiable which does not require urgent evaluation or treatment and but can be addressed as a psychiatric inpatient.
See Screening for Organic illness in disturbed patients