When you apply for a CDL, your state DMV will ask you to self-certify into one of four federally defined driving categories. The category determines whether you must hold a current DOT medical card and what kinds of routes you're authorized to drive. Choose carefully — you can change your certification later, but each change requires submitting fresh documentation.
Non-Excepted Interstate (NI)
This is the category most CDL holders fall into. NI authorizes you to operate a commercial motor vehicle in interstate commerce — across state lines, or domestically as part of a chain of interstate commerce — and requires a current DOT medical examiner's certificate. Choose NI if you'll work for any company that ever crosses state lines, including most over-the-road, regional, and local trucking jobs.
Excepted Interstate (EI)
EI authorizes interstate operation but only in narrow categories that are exempt from federal medical-card requirements: certain federal, state, or local government employees; transport between farm and market within 150 air miles of the source; certain custom-harvesting and bee-keeping operations; transport of human corpses or sick/injured persons. EI drivers do not have to maintain a DOT medical card. Very few applicants qualify.
Non-Excepted Intrastate (NA)
NA authorizes operation only within your home state and requires whatever medical certification your state requires (often a state-equivalent of the federal DOT physical, sometimes more lenient). Choose NA only if you're certain you'll never cross state lines for work — and remember that "delivering a load that originated in another state" can constitute interstate commerce even if you never personally cross a state line.
Excepted Intrastate (EA)
EA authorizes intrastate operation only and is exempt from medical-card requirements. The categories that qualify (similar to EI) are very narrow.
Recommendation
Self-certify as NI unless you're 100% certain you qualify for one of the excepted categories. The flexibility to take a different job — including any job that involves loads originating outside your state — is almost always worth the small inconvenience of maintaining a current medical card.