Passing the CDL knowledge test is only one of the requirements. Most commercial drivers also have to be medically certified before they can legally drive a commercial motor vehicle (CMV), and that certification is what people mean by the "DOT medical card." The rules come from the Federal Motor Carrier Safety Administration (FMCSA), in 49 CFR Part 391.
First: which kind of driving will you do?
When you apply for a commercial learner's permit (CLP) or CDL, federal rules require you to certify to your state which of four types of operation you expect to drive in:
- Non-excepted interstate: you cross state lines (or haul freight that does) and you are subject to the federal driver qualification rules. This is most over-the-road truck drivers, and it is the category that must have a medical examiner's certificate.
- Excepted interstate: interstate driving, but only in operations the federal rules exempt from the medical requirement.
- Non-excepted intrastate: driving only within your state, under your state's own driver qualification rules.
- Excepted intrastate: in-state driving in operations your state exempts.
If you are not sure which box fits, ask your employer or your state licensing agency before you apply. Choosing the wrong one can lead to a downgraded license later.
Related: What to Expect on the CDL General Knowledge Test
Who can do the exam
The exam has to be done by a medical examiner listed on FMCSA's National Registry of Certified Medical Examiners. Not every doctor's office qualifies, so check that the examiner is on the registry before you book.
What the examiner checks
The physical qualification standards are listed in 49 CFR 391.41. Among them, a driver must:
- See well enough: at least 20/40 in each eye and in both eyes together, with or without corrective lenses; a field of vision of at least 70 degrees horizontally in each eye; and the ability to recognize the red, green and amber of traffic signals.
- Hear well enough: perceive a forced whisper at 5 feet or more in the better ear, with or without a hearing aid, or pass the audiometric equivalent.
- Not have a condition likely to interfere with safe driving: the rules name cardiovascular disease that can cause fainting or collapse, high blood pressure likely to interfere with safe driving, respiratory problems, epilepsy or any condition likely to cause loss of consciousness, and certain limb impairments.
- Not use certain drugs: no Schedule I drugs, amphetamines, narcotics or other habit-forming drugs, unless a prescribing practitioner familiar with your history has advised that a prescribed substance will not affect your driving.
Insulin-treated diabetes and vision that does not meet the standard in one eye are not automatic disqualifications; each has its own federal standard, with a shorter certification period.
How long the certificate lasts
Under 49 CFR 391.45, a driver must be re-examined if they have not been medically examined and certified during the preceding 24 months. That is the maximum; an examiner can certify you for a shorter period if a condition needs monitoring. Drivers certified under the insulin-treated diabetes standard or the alternative vision standard must be re-examined every 12 months.
If your certificate lapses while you certify as non-excepted interstate, your state can downgrade your CDL, so put the expiration date on your calendar.
How the certificate reaches your state
Since June 23, 2025, medical examiners send exam results to FMCSA electronically, and FMCSA passes them to your state, which records your medical status on your driving record. Check with your state licensing agency on whether it still wants a copy from you as well.
What this means for your test
The medical card is not on the knowledge test itself, but it can hold up your permit. Many applicants get the exam done early, then focus on the general knowledge test.