They are a chiropractor Please Register or Log in to view the hidden image! If they refer to themselves as Dr and then use a first name they are a chiropractor. Other than in a medical setting no other doctors refer to themselves that way or as a doctor at all. Have you encountered any exceptions? Please Register or Log in to view the hidden image!
Veterinarians refer to themselves as doctors. So do ophthalmologists and optometrists. In the USA, anyone who has a genuine university degree at the doctoral level (M.D., Ph.D., D.Sc., etc.) can legally identify himself as a doctor, for the obvious reason that he IS a doctor! However, in common practice, only people who actually deal with medicine (human medicine, veterinary medicine, ophthalmology or optometry) call themselves doctors.