The fun, creative, active side?

My husband has begun the process of getting a diagnosis. I'm a little confused and would love some enlightenment. His primary care physician saw him, then asked to also see me. After asking a lot of questions, he said he didn't have a problem putting him on a low dose of ritalin and checking back in 4 weeks.

My husband's next step was to see our counselor, who said it probably was the best course of action. He said there is no test for ADHD and if the medicine is helping him sleep, clearing his head, helping with temper and impulse control--rather than making him jittery and high--then he probably needs to be on it.

Is this the way people are diagnosed?

I am also concerned when I read about the bundle of energy, creative, fun side of people with ADHD. That is not my husband at all and never has been. Quiet, reserved--but apparently with a mind that raced 100 miles per hour all the time. Poor memory, low self-esteem, no control over what he says, zones out when people talk, can't concentrate on what he reads or hears in a meeting--all that,  yes. Can it still mean ADHD or could it be something else?