Getting a diagnosis for adult ADHD can be challenging for everyone involved. Because there is no lab test that provides diagnostic certainty, physicians must use a variety of tools and piece together a diagnosis like a puzzle. They rely on professional observations and information gleaned from a physical exam, patient interviews, school reports, test results and job evaluations, and blood tests to rule out conditions with similar symptoms, such as thyroid disease. Other tests and evaluations can determine if learning disorders or neurological problems are involved.