Dreaming of a hospital can signify an emergency or something drastic that has happened. Trips to the hospital usually come when something physical has occurred. Thus, the dreaming of a hospital may be a sign of shock that has come into your life, something unexpected and unplanned that requires immediate attention. Also, it can be interpreted as a sign that you need to try your best to improve your health both mentally and physically.
Of course, it is not necessarily a bad event. While most trips to the hospital are for emergency medical treatment, visits to there may also be for good such as the birth of a child. While still requiring professional and medical help, it is a time of great joy.