How often you need a DOT physical: the eight cases in 49 CFR 391.45

"Every two years" is the answer most drivers are given, and it is the default rather than the rule. 49 CFR 391.45 lists eight separate situations that trigger an examination, and five of them run on a shorter clock or no clock at all. Knowing which one you are in is the difference between a valid certificate and an unexpected downgrade at a roadside inspection.

The structure of the section

Section 391.45 does not set an expiry date on a certificate. It lists the persons who must be medically examined and certified in accordance with 391.43 as physically qualified to operate a commercial motor vehicle. Each paragraph is a category of person, and the shortest applicable one governs. The section opens with the phrase "the following persons", and then works through paragraphs (a) to (h).

(a) Never examined

Any person who has not been medically examined and certified as physically qualified to operate a commercial motor vehicle. The obvious first case, and the reason a new driver's first appointment is not a renewal of anything.

(b) The 24-month default

Any driver who has not been examined and certified as qualified during the preceding 24 months — unless the driver is required to be examined under paragraph (c), (e), (f), (g) or (h) instead. That exclusion list is doing real work: five other paragraphs override the two-year rule, and the section says so on its face.

(c) Exempt intracity zone: 12 months

Any driver authorized to operate a commercial motor vehicle only within an exempt intracity zone under 391.62, if that driver has not been examined and certified to drive in such a zone during the preceding 12 months. Half the default interval. This pairs with 391.43(d), which requires such a driver to furnish the examiner with a copy of the medical findings that led to the first certificate allowing operation wholly within the zone — so bring the old paperwork.

(d) Reserved

Paragraph (d) is marked [Reserved] in the current text. It is not a gap in the requirements; it is a numbering placeholder.

(e) Insulin-treated diabetes: 12 months

Any driver who has diabetes mellitus treated with insulin for control and who has obtained a certificate under the standards in 391.46, if the most recent examination and certification did not occur during the preceding 12 months. This follows from 391.41(b)(3), which excludes insulin-treated diabetes from the general standard "unless the person meets the requirements in 391.46". The route exists; it comes with an annual cycle.

(f) Vision alternative standard: 12 months

Any driver who does not satisfy, with the worse eye, either the distant visual acuity standard with corrective lenses or the field of vision standard in 391.41(b)(10)(i), or both, and who has obtained a certificate under 391.44, if the most recent examination did not occur during the preceding 12 months. Same structure as the diabetes case: an alternative standard with an annual interval.

(g) After an injury or illness: no fixed interval

Any driver whose ability to perform his or her normal duties has been impaired by a physical or mental injury or disease. There is no period attached to this paragraph at all. The trigger is the impairment, which means a valid unexpired certificate does not by itself answer the question after a significant injury or a new diagnosis.

(h) After a finding of not qualified

On or after 23 June 2025, any person found by a medical examiner not to be physically qualified under 391.43(g)(3). Read this together with what 391.43(g)(3) itself does: when the examiner finds the person not physically qualified, it must be reported to FMCSA and all medical examiner's certificates previously issued to that person are no longer valid and no longer satisfy 391.41(a). A failed examination therefore does not leave the previous card running to its printed expiry date. It ends it.

Putting the eight cases together

The practical reading is:

• 24 months is the default, under 391.45(b), and only when none of (c), (e), (f), (g) or (h) applies.
• 12 months for the exempt intracity zone (c), insulin-treated diabetes under 391.46 (e), and the vision alternative standard under 391.44 (f).
• No interval, examine on the event for impairment by injury or disease (g), and for a not-qualified finding (h).
• An examiner may also certify for a shorter period than the maximum on clinical grounds. The section sets the outer bound at which an examination becomes mandatory; it does not stop a certificate being issued for less.

Where the certificate lives, and who has to hold it

Three separate obligations are easy to conflate.

• Carrying it. Under 391.41(a)(2)(i)(B), on or after 23 June 2025 a CDL or CLP holder with a current certificate no longer has to carry it. A driver not required to hold a CDL is still covered by the general rule in 391.41(a)(1)(i) and carries the original or a copy when on duty. Anyone qualifying by a medical variance carries a copy of the variance documentation under 391.41(a)(1)(ii).
• The examiner's file. Under 391.43(i), the examiner retains the original Medical Examination Report and a copy of the certificate for at least three years, and must produce them to an authorized enforcement representative within 48 hours of a request.
• Which record wins. Under 391.41(a)(2)(iv), where the electronic medical certification information FMCSA provides conflicts with a paper copy of the certificate, the electronic information controls.

Practical scheduling

None of the following is in the regulation; it follows from it.

• Book before the interval runs out, not on the day. 391.43(g)(4) allows an examiner to delay a determination for up to 45 days to obtain more information or conduct a further examination. If that happens on the last valid day, the driver is out of certification while it is resolved.
• If you are on a 12-month cycle, treat it as 12 months. Paragraphs (c), (e) and (f) override the 24-month default entirely, and the certificate's own validity period will reflect that.
• After any significant injury or new diagnosis, ask. Paragraph (g) has no interval, so the unexpired card in your wallet is not the answer.
• If an examination goes badly, do not assume the old card still runs. 391.43(g)(3) invalidates previously issued certificates on a not-qualified finding.

Every clinic listing in this directory shows the certification dates its source register publishes plus the date we last checked the record. Use it to find and compare clinics; verify an individual examiner's current listing against the National Registry itself.