(Note: My son has diagnosed ADHD, non-hyperactive) There isn't a blood test, but you can do a neuropsychological evaluation which assesses cognitive functions. We had one done for my son, and it was a 2-day affair. As a non-ADHD parent, it was eye-opening to get a glimpse into how his brain worked and to start to really understand the challenges ADHD poses in a school environment.

You get assessed by a medical professional equipped to evaluate you, just like any neurodevelopment issue.