Occupation on immigration records

I think I found one of my ancestor's immigration records, he had a really unique name so there's very little chance it isn't him, but his occupation is listed as "doctor of medicine." After he arrived in the States, he never had a job other than (Civil War) soldier and generic laborer. I don't know which is more likely, did he lie when he immigrated, or is there a chance he really was a doctor in Germany and just couldn't practice in America?