Nurses who have completed a master of science degree in nursing (MSN) may wish to further their education by completing a doctoral program. Three common program choices are the doctor of nursing practice, the Ph.D. in nursing and a medical doctorate.

Doctor of Nursing Practice

Doctor of nursing practice (DNP) is a doctoral program that prepares nurses for advanced practice and leadership in the field. Students typically have completed a master's degree in nursing before beginning a DNP program, though some schools consider post-bachelor's applicants. The American Association of Colleges of Nursing, which establishes standards for nursing programs, requires that DNP programs consist of at least 12 months of full-time study. Students without a master's degree must complete at least 36 months of full-time study.

Ph.D. in Nursing

The Ph.D. in nursing prepares students to be scientific researchers and nurse educators. Most applicants enter the Ph.D. program having already earned a master's degree, but some programs admit exceptional students with only a bachelor's degree. The time needed to complete a Ph.D. varies, depending on how long it takes a student to prepare and defend his dissertation. However, nursing schools typically advise students that a Ph.D. program will take at least four years to complete.

Medical Doctor

Medical school is four years in length, followed by a three-year residency. A student with an MSN may have an advantage over her peers in familiarity with patient care, but credits earned in a nursing program do not substitute for medical school courses. Students may also need to take basic science classes before applying to medical school if they didn't successfully complete those courses in their undergraduate years. This can add a semester or more to the time needed to complete the degree.