"My boyfriend suffers majorly from delusions of grandeur..."

My boyfriend suffers majorly from delusions of grandeur and he sees things religiously and thinks he's a profit here to preach through his mind to others and that he controls everything and very powerful. A lot of odd things occur when he is driving like asking did you see that eagle sent from god? I'm just wondering if there is anything we can do to lesson these symptoms! It's over bearing and annoying. Please help I love him a lot!
The following are speaking in general, not specifically to this case as advice cannot be rendered without seeing the person in person: Mania is a medical emergency, and if severe (psychotic symptoms - beliefs or experiences that no one else believes or experiences) can require hospitalization, although only a physician seeing him first-hand can determine that. Medication and talking therapy are both necessary in follow-up after time in hospital. Involvement with the family helps address insight issues, or lack there of, during manic episodes. The goal of treatment is to have a "therapeutic relationship", or mutual respect between patient and health care provider.