Late life onset of bipolar disorder is uncommon, and may actually be a neurological disease rather than bipolar. Delirium in elderly patients can manifest in symptoms that resemble bipolar disorder, and health professionals need to rule out delirium as a cause of certain behaviours. Another factor in bipolar diagnosis in the elderly is the prevalence of alcohol abuse and overuse of prescription sedatives.  Psychosis, agitation, paranoia, sleep disturbance and hostility are symptoms common to both bipolar and neurological diseases, making diagnosis more difficult.
 
There are three general ways an elder is diagnosed with bipolar: when there has already been a bipolar diagnosis earlier in life; when the elder has already been diagnosed with depression and is now exhibiting symptoms of mania; and patients who are now displaying signs of mania. Once diagnosed and prescribed medication, elderly consumers are at higher risk of discontinuing the medication because of non-compliance, a new health problem, death of a caregiver or of other supports, or because the particular medication may not complement other medications already being taken by the patient.