Adults are tested for ADHD through a comprehensive diagnostic evaluation conducted by a qualified mental health professional. This includes a detailed patient interview, review of the individual's personal, medical, and psychiatric history (including childhood), and often an interview with a close family member or someone who knows the person well to collect additional behavioral information. Rating scales or ADHD behavior questionnaires are commonly used for both the patient and an informant to assess symptom frequency and severity compared to typical adults. A medical examination may also be performed to rule out other conditions that mimic ADHD symptoms. There is no single medical or genetic test for ADHD in adults; diagnosis relies on clinical judgment and standardized criteria like those in the DSM-5.

Typical ADHD testing includes:

• Patient interview and history review
• Interview of a family member or close associate
• Use of behavior rating scales/questionnaires (e.g., Adult Self-Report Scale, CAARS)
• Medical evaluation to exclude other conditions
• Assessment of symptom impact on daily life

Some practitioners may also utilize computerized tests like the Conners Continuous Performance Test (CPT3) to evaluate attention performance, impulsivity, and vigilance, though these are part of a broader assessment process.