The Commission on Dietetic Registration (CDR) of the American Dietetic Association (ADA) offers a Registered Dietitian certification. To qualify, you must complete a four-year degree in nutrition or a related field. You must also complete a supervised practice program, which is accredited by the Commission on Accreditation for Dietetics Education or the ADA. Some college programs will include the accredited supervised practice program as part of the degree. After you have met these requirements, then you will be able to take the Registration Examination for Dietitians.
The CDR offers a Dietetic Technician, Registered (DTR) certification. To earn a DTR certification, you need to have an associate degree in nutrition or a related field. You also need to complete 450 supervised practice hours through a dietetic technician program, which has been accredited by the ADA. After meeting these degree and program requirements, then you can take the Registration Examination for Dietetic Technicians.
If you earned your bachelor's degree and obtained your RN certification, then you have the opportunity to become board certified by the CDR in several areas. These include pediatric nutrition, renal nutrition, oncology nutrition, sports dietetics and gerontological nutrition. The different board certifications have different requirements, but they generally include holding your RN certification for a minimum number of years, and completing a certain number of practice hours in your specialty area. Education, such as a master's degree in nutrition, can be used toward a certain percentage of those practice hours.
The CDR is very strict about the term "Registered Dietitian Eligible." Completing your bachelor's degree and the supervised practice hours makes you eligible for entering into the RD certification process leading up to taking your examination. However, eligibility is not a credential in and of itself, and the CDR is very much against dietitians using the term to describe themselves.