Drug testing is required before you can hold a commercial driver's license, and the rules are set by the Federal Motor Carrier Safety Administration

Before you receive a CDL, you must pass a drug test ordered by your employer or the testing service they hire. This is not optional — it is a federal requirement under 49 CFR Part 382. The test screens for five drug categories: marijuana, cocaine, amphetamines, opioids, and phencyclidine (PCP). You pay for the test yourself, though some employers cover the cost.

The test must happen before you drive a commercial vehicle for the first time. If you fail, you cannot obtain or renew your CDL. If you pass, the result is valid for your CDL process but does not carry over if you explore for a CDL in a different state — each state's licensing authority sets its own testing timeline and procedures.

The testing process is straightforward: you go to a Department of Transportation (DOT)-certified testing facility, provide a urine sample, and receive results within a few days. The facility reports the result to your employer or the licensing authority, depending on who ordered the test. You have the right to request a retest at your own expense if you believe the result is wrong.

Key Takeaways

  • Federal law requires a drug test before you can obtain a CDL, and you must pass to be licensed.
  • The test screens for marijuana, cocaine, amphetamines, opioids, and PCP using a urine sample at a DOT-certified facility.
  • You pay for the test, though some employers will cover it as part of hiring.
  • A positive result blocks CDL issuance, but you can request a retest at your own expense if you dispute the finding.
  • Each state's licensing authority may have additional testing rules beyond the federal minimum.

Who orders the test and when it happens

Your employer or the company sponsoring your CDL training typically orders the test. If you are explore for a CDL on your own without an employer, you may need to arrange it through a third-party testing service or your state's licensing authority — contact your state's Department of Motor Vehicles to confirm their process.

The test must occur before you start driving commercially. Most employers schedule it as part of the hiring process, after a conditional job offer but before your first day. Some states require the test result to be submitted with your CDL process; others allow you to show proof of a passing test when you take your written and skills exams at the DMV.

The timing varies by state and employer. In some cases, the test happens within days of your job offer. In others, it may be scheduled weeks in advance if the testing facility has a backlog. Ask your employer or the testing service for their current timeline so you know when to expect results.

What happens if you test positive

A positive result means you cannot obtain a CDL. You will not be hired, and your process will be denied. There is no appeal process within the licensing system — the result stands as reported by the testing facility.

However, you have the right to request a confirmatory retest at your own expense. If the initial test was a screening test (which is common), you can ask for a more precise laboratory test to verify the result. You must request this retest within a set timeframe — usually 72 hours — so act quickly if you believe the result is wrong. The retest is paid by you and takes longer, but if it comes back negative, you can use that result to reapply for your CDL.

If you genuinely tested positive due to a prescription medication, bring documentation of the prescription to the testing facility or your employer. Some medications can produce a positive result for opioids or amphetamines. The facility may note this in your record, though the initial result may still block your CDL unless you pursue a retest.

State-specific testing rules and timing

While federal law sets the baseline, individual states add their own requirements. Some states require the test result to be submitted before you take your CDL skills test. Others allow you to take the written exam first and submit the test result later, as long as it is done before you receive your license.

A few states conduct their own drug testing as part of the licensing process, separate from the employer-ordered test. Check with your state's DMV to learn whether you need one test, two tests, or if the employer's test satisfies the state requirement.

The cost of the test ranges from $30 to $100 depending on the facility and your location. Some employers cover this as a hiring expense; others deduct it from your first paycheck or require you to pay upfront. Confirm the cost and payment method with your employer or the testing service before you go to the facility.

Retesting and challenging a positive result

If you receive a positive result and believe it is wrong, request a confirmatory retest when ready. The initial screening test is less precise than a laboratory confirmation test, so a retest can sometimes overturn the result. You must pay for the retest yourself, and it typically costs $100 to $200.

Request the retest in writing or by phone to the testing facility that conducted the initial test. Ask for a gas chromatography/mass spectrometry (GC/MS) test, which is the gold standard for drug testing. Provide your name, date of birth, and the date of your initial test. The facility will schedule you for the retest, which usually happens within one to two weeks.

If the retest comes back negative, you can use that result to reapply for your CDL. Bring a copy of the negative retest result to your state's DMV along with your other CDL process materials. The negative result overrides the positive screening test.

Medical review officers and prescription medications

Some testing facilities employ a Medical Review Officer (MRO) — a licensed physician who reviews positive results and asks whether you are taking any prescription or over-the-counter medications that could explain the result. If you tested positive and the facility contacts you, be honest about any medications you take.

Certain prescriptions can produce a positive result for opioids (painkillers, cough syrup with codeine) or amphetamines (ADHD medications, decongestants). The MRO will note this in your record, but the initial positive result may still block your CDL unless you pursue a retest or the MRO determines the medication fully explains the result.

If you know you take a medication that could affect the test, tell your employer and the testing facility before you take the test. Bring a copy of your prescription or a letter from your doctor. This does not may provide you will pass, but it creates a record that may help if the result is positive.

What the test does and does not cover

The DOT drug test screens for five substances: marijuana, cocaine, amphetamines, opioids, and PCP. It does not test for alcohol, benzodiazepines (anti-anxiety medications), barbiturates, or other drugs. If your employer wants to test for additional substances, they must order a separate, non-DOT test at their own expense.

The test uses a urine sample, not blood or hair. You will be asked to provide a sample in a private bathroom at the testing facility. A technician may observe the sample collection to prevent tampering, though this varies by facility. The sample is sealed and sent to a laboratory for analysis.

The test is designed to detect drug use within the past two to three days for most substances, though marijuana can be detected longer depending on frequency of use. The test does not measure impairment — only the presence of the drug in your system.

Frequently Asked Questions

Can I refuse to take the drug test?

No. Refusing the test is treated the same as a positive result — you will not be hired and your CDL will be denied. If you are already employed and refuse a test ordered by your employer, you can be fired. The test is a legal requirement, not optional.

How long does it take to get the results?

Screening test results usually come back within three to five business days. If you request a confirmatory retest, that takes one to two weeks. Some employers and testing facilities offer expedited results for an additional fee, but standard timing is about a week from sample collection to final result.

What if I take CBD or hemp products?

CBD and hemp products contain little to no THC and should not produce a positive result on a DOT drug test. However, some products are mislabeled or contaminated with THC. If you use CBD and test positive for marijuana, request a confirmatory retest. The retest is more precise and may show a negative result if the THC level is below the testing threshold.

Can I get my CDL if I have a past drug conviction?

A past conviction does not automatically disqualify you from a CDL, but you must pass the current drug test. The test looks at your current drug use, not your history. If you have been in recovery, passing the test is what matters for CDL purposes.

Do I have to disclose the test result to anyone besides my employer?

Your employer and the testing facility know the result. Your state's DMV may also receive it if the state requires the result as part of the CDL process. You do not have to disclose it to anyone else, and it does not appear on your driving record or criminal record — it is a separate employment and licensing document.