Can Attention Defict Disorder Be Considered a Disability?

My husband got previously fired from an old job because he was not meeting the required account reviews per day. His current job he is getting into the same situation. He tries his best to go as the same pace as everyone else but is lacking behind. His supervisor warned him stating if he does not catch up she will fire him. My husband has ADD. It can get very hard for him to concentrate at times especially if it is the same thing over and over again. I can understand where his sup is comming from but I also want my husband to be protected.