Do all medical doctors have a PhD?

Not necessarily. Medical doctors all have an MD or DO (at least in the U.S.). That, along with a license, are what is required to practice medicine and treat patients. Some physicians also have a PhD. read more

No. Some do though. Most medical doctors have either an MD (Doctor of Medicine) or an MBBS (Bachelor of Medicine/Bachelor of Surgery). They are effectively equal qualifications. I know a few medical doctors who also have a PhD, and they are all brilliantly intelligent. They do have to put up with the occasional joke about being "Doctor Doctor" though. read more

Depending on the type of medical specialty or Ph.D. field of specialization, both physicians and doctors of philosophy might spend the same amount of time in school. A physician may earn a Ph.D. in a related field, but is not required to do so to practice medicine. read more