How is it possible to know if I have attention-deficit/hyperactivity disorder adhd?

Symptoms. If you have the symptoms of adhd, as dr. Ali answered, then you may have the disorder. Check with your doctor for an evaluation or referral. See chadd.Org or nimh site: http://www.Nimh.Nih.Gov/health/publications/attention-deficit-hyperactivity-disorder/can-adults-have-adhd.Shtml. I've got a copy on my health files.
Adhd. Inattention, overactivity, impulsivity. For example, not finishing tasks, easily distracted, forgetful, disorganized, losing things, act before thinking, etc.