5 Reasons Drivers Fail the DOT Exam

Failing your DOT exam can put your livelihood on hold. The good news is that most failures are not permanent and are highly preventable — they usually come down to a handful of issues you can address with a little preparation. Here are the five most common reasons drivers run into trouble, and how to avoid each one.

1. Elevated Blood Pressure: This is the number one cause of delays. Stress — sometimes called white coat syndrome — along with caffeine or a skipped dose of medication can push readings over the 140/90 threshold. To give yourself the best shot, drink plenty of water, arrive 15 minutes early so you can sit and relax, avoid caffeine beforehand, and take your prescribed blood pressure medication on your normal schedule.

2. Missing Prescription or Treatment Documentation: If you manage high blood pressure, diabetes, a heart condition, or sleep apnea, the examiner is required to see supporting documentation before certifying you. Bring clearance letters from your treating doctor and, for sleep apnea, CPAP compliance logs showing consistent use — generally at least 70% of nights over the past 90 days. Walking in without this paperwork is one of the most common reasons an exam stalls.

3. High Sugar in the Urinalysis: Elevated glucose in your urine sample can signal uncontrolled diabetes. If you are diabetic, keep your blood sugar well-managed in the days before your exam and bring your most recent HbA1c results — the certificate generally requires it to be under 10%. Good control not only protects your certification, it protects your long-term health on the road.

4. Vision Deficiencies: Federal rules require at least 20/40 vision in each eye, with or without correction. If your eyesight has slipped, your current glasses may no longer get you there. If you suspect your vision has changed, get an eye exam and an updated prescription before your DOT physical so you arrive ready to meet the standard.

5. Incomplete or Inaccurate Health History: The MCSA-5875 history form is part of your exam, and the examiner relies on it. Leaving off a medication or a known condition may seem like it speeds things up, but it can invalidate your certificate later and create bigger problems. Disclose your full history and bring the paperwork that clears you — honesty paired with documentation is what gets you certified.

What Failing Usually Means: In most cases, not passing on the first visit is actually a temporary deferral, not a permanent disqualification. The examiner gives you a clear list of what to resolve — a specialist clearance letter, updated lab work, or a medication adjustment — so you know exactly what to fix.

What Happens If You Are Deferred: A deferral simply means the examiner needs more information before certifying you. Gather the requested documentation from your treating doctor, and if you need a follow-up visit to complete your certification, call ahead to confirm the clinic process for deferred drivers. Once the outstanding item is resolved, you can be re-examined and certified.

The bottom line: preparation is everything. Hydrate, skip the caffeine, manage your known conditions, bring your documentation, and be upfront about your health history. Do those five things and the vast majority of drivers pass without delay. If you are unsure how a specific condition might affect your exam, call our Phoenix or Tolleson office before you come in and we will tell you exactly what to bring.