There are no blood tests or imaging studies that will diagnose OCD. The doctor or mental health professional will ask you about your thoughts, behavior and past history as well as family history.
The diagnostic criteria for obsessive-compulsive disorder according to the DSM-IV are:
1. Either obsessions or compulsions
2. The obsessions or compulsions are time-consuming (more than one hour per day), cause clinically significant distress, or interfere with a person’s daily routine and occupational or social functioning.
Psychological testing may be recommended to rule out other disorders or to diagnose other disorders you may have instead or in addition.