There is no A1C limit for a DOT physical written into federal regulation. The FMCSA declined to put a specific number in its diabetes rule, saying that qualification decisions should not rest on an A1C value alone.1Federal Register. Qualifications of Drivers; Diabetes Standard In practice, though, an A1C above 10% is the level the agency’s own Medical Review Board has flagged as evidence of uncontrolled diabetes, and readings in the 8% to 10% range often lead examiners to look harder or issue a shorter certificate.
Why A1C Still Matters Even Without a Legal Cutoff
A1C (also called HbA1C or glycated hemoglobin) reflects your average blood sugar over roughly two to three months. A single finger-stick reading shows a moment; A1C shows a pattern. For a commercial driver, the concern is straightforward. Poorly controlled blood sugar raises the risk of a hypoglycemic episode behind the wheel, and that can mean loss of consciousness, blurred vision, or slowed reaction time. Diabetes-related nerve damage and eye disease compound that risk over time.
So even without a bright-line number in the rulebook, your A1C is a signal the medical examiner uses to judge whether your diabetes is stable enough for you to hold a certificate.
Where the 10% and 8% Numbers Come From
Plenty of websites claim 8% is the cutoff. That figure does not appear in FMCSA regulations or official guidance. It likely traces back to general diabetes management goals set by medical organizations rather than the Department of Transportation.
The federal record tells a different story. When FMCSA developed its insulin-treated diabetes rule, the Medical Review Board recommended treating an A1C above 10% as evidence of uncontrolled diabetes and grounds for disqualification, with reinstatement once the level dropped back to 10% or below. FMCSA’s former exemption program for insulin-using drivers separately required an endocrinologist evaluation showing an A1C between 7% and 10%.1Federal Register. Qualifications of Drivers; Diabetes Standard
FMCSA ultimately declined to write either number into the final rule. The agency agreed with commenters that A1C should not be relied on as a sole measure of whether someone can safely operate a commercial vehicle.1Federal Register. Qualifications of Drivers; Diabetes Standard So no number automatically disqualifies you, but 10% is the level examiners are most likely to treat as a red flag.
How the Examiner Uses Your A1C
The certified medical examiner considers your A1C alongside everything else in your file: glucose monitoring records, complication history, medication stability, vision, cardiovascular fitness, and overall health. The A1C result should be from within the preceding three months.1Federal Register. Qualifications of Drivers; Diabetes Standard
What the number tends to mean in practice:
- Well below 8%, with a stable insulin regimen or effective non-insulin treatment: usually the smoothest path to a full-length certificate.
- 8% to 10%: closer scrutiny, more documentation requests, and sometimes a shorter certification period so the examiner can check in sooner.
- Above 10%: the level the Medical Review Board tied to uncontrolled diabetes. Expect denial or a very short certificate until you bring the number down.
Even a driver not on insulin can be asked for A1C lab results if something on the physical raises a concern. The medical examiner evaluates non-insulin diabetes case by case and can request labs from your treating provider.2Federal Motor Carrier Safety Administration. Medical Examiners Handbook 2024 Edition FMCSA guidance recommends annual re-certification for diabetic drivers even without insulin.3Federal Motor Carrier Safety Administration. May a Driver Who Has Non-Insulin Treated Diabetes Mellitus Be Certified?
The maximum certificate length is 12 months for insulin-treated drivers, compared with 2 years for drivers without disqualifying conditions.4Federal Motor Carrier Safety Administration. For How Long Is My Medical Certificate Valid? The examiner can issue a shorter certificate when the situation calls for one.
Extra Rules if You Use Insulin
If you take insulin, 49 CFR 391.46 layers additional requirements on top of the standard DOT physical.5eCFR. 49 CFR 391.46 Physical Qualification Standards for an Individual With Diabetes Mellitus Treated With Insulin for Control Your A1C sits inside a larger picture that has to check out:
- A stable insulin regimen with properly controlled blood sugar. An examiner who finds otherwise cannot certify you.
- No severe non-proliferative diabetic retinopathy and no proliferative diabetic retinopathy. Either diagnosis permanently disqualifies you from commercial driving.
- No recent severe hypoglycemic episode, meaning one requiring the assistance of others or resulting in loss of consciousness, seizure, or coma.
- All other physical standards in 49 CFR 391.41, including vision (at least 20/40 in each eye, 70-degree horizontal field, and ability to distinguish red, green, and amber signal colors), hearing, blood pressure, and cardiovascular fitness.6eCFR. 49 CFR 391.41 Physical Qualifications for Drivers
Your treating clinician documents all of this on the Insulin-Treated Diabetes Mellitus Assessment Form, MCSA-5870, including your most recent A1C.7Federal Motor Carrier Safety Administration. Insulin-Treated Diabetes Mellitus Assessment Form, MCSA-5870 The examiner must begin your DOT physical within 45 calendar days of the clinician’s signature or the form expires. To qualify for the full 12-month certificate, you also need at least three months of electronic blood glucose self-monitoring records generated while on insulin. Without those, the examiner can certify you for no more than three months while you build the history.8Federal Motor Carrier Safety Administration. Insulin-Treated Diabetes Mellitus Assessment Form MCSA-5870
If a severe hypoglycemic episode happens after you are certified, you must stop driving immediately. Driving resumes only after your treating clinician identifies the cause, confirms you are back on a stable regimen with properly controlled diabetes, and completes a new MCSA-5870.5eCFR. 49 CFR 391.46 Physical Qualification Standards for an Individual With Diabetes Mellitus Treated With Insulin for Control
If Your A1C Is High Before Your Exam
If your most recent A1C is above 10%, or high enough in the 8% to 10% range that you are worried about certification, work with your treating clinician before you sit for the physical. Bringing the number down through medication adjustments, consistent glucose monitoring, and diet takes time, which is exactly what A1C measures. A cleaner reading paired with three months of solid electronic monitoring records gives the examiner the fullest basis for a longer certificate.
A denial is not the end of the road. If the examiner concludes your diabetes poses too much risk at the moment, you can address the underlying issue with your clinician and return for re-evaluation once your numbers and documentation support certification.