What Is BZO on a Drug Test? Benzodiazepine Screening Explained

What is BZO on a drug test? BZO is the standard abbreviation for benzodiazepines, a class of prescription sedatives that includes alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan) and clonazepam (Klonopin). When you see BZO on a drug test cup, dip card or lab report, it marks the panel that screens urine for benzodiazepines. On most rapid tests it is printed as BZO/300, meaning a screening cutoff of 300 ng/mL.

BZO is a class panel, not a single-drug test. It reacts to many benzodiazepines, but not equally to all of them, and that difference is the most important thing to understand before relying on a BZO result. This guide explains what the BZO panel detects, what the cutoff means, which benzodiazepines are harder to catch, how to read the result and which test formats include it.

What Is BZO on a Drug Test?

BZO stands for benzodiazepines. Some manufacturers and labs use BZD or BENZ for the same class, so a lab report may look different from the label on a cup. All three refer to the benzodiazepine screen.

For other codes on the same cup, see the full drug test abbreviations chart.

What Drugs Does the BZO Panel Detect?

Benzodiazepines are prescribed for anxiety, panic disorder, insomnia, seizures and alcohol withdrawal. Common examples include:

• Alprazolam (Xanax)
• Diazepam (Valium)
• Lorazepam (Ativan)
• Clonazepam (Klonopin)
• Temazepam (Restoril) and chlordiazepoxide (Librium)

Rapid BZO tests are immunoassays. The antibody on the strip is usually calibrated to one reference compound, such as oxazepam or nordiazepam, and then cross-reacts with other benzodiazepines to different degrees. Drugs that are metabolized to oxazepam-type compounds, such as diazepam and temazepam, tend to be picked up well. The FDA has also strengthened warnings about benzodiazepine misuse and dependence, which is one reason clinics and treatment programs track this class closely (FDA benzodiazepine boxed warning).

Why Some Benzodiazepines Are Harder to Detect

Clonazepam and lorazepam are two of the most commonly prescribed benzodiazepines, yet many rapid immunoassays respond to them weakly. Clonazepam is taken in small doses and excreted mostly as 7-aminoclonazepam, and lorazepam is excreted largely as a glucuronide conjugate. Both can stay below a 300 ng/mL screening threshold even when the person is taking the medication.

In practice, this means a negative BZO screen does not prove that no benzodiazepine was taken. Programs that need to monitor a specific prescription, such as pain management or opioid treatment clinics, often send samples for laboratory testing that measures the individual drugs. The cross-reactivity table in the package insert shows how strongly your specific device responds to each benzodiazepine.

Common Benzodiazepines and How a BZO Screen Responds

How well a rapid screen detects a benzodiazepine depends largely on what the body turns it into. This table is a general guide; the cross-reactivity table in your device’s insert is the final word.

What Can Cause a False-Positive BZO Screen?

False positives on benzodiazepine immunoassays are uncommon but documented. The antidepressant sertraline and the anti-inflammatory oxaprozin are among the medications most often reported, and the HIV medication efavirenz has also been linked to false-positive results on some assays. The University of Rochester Medical Center notes that some NSAIDs and sertraline can affect benzodiazepine urine results. Because reports vary by assay, a donor’s medication list should be reviewed during confirmation, not used to dismiss a result at the collection site.

What Does BZO/300 Mean? Understanding the Cutoff

The number after the abbreviation is the cutoff concentration in nanograms per milliliter. On a BZO/300 test, the sample must contain benzodiazepines (as measured against the reference compound) at or above 300 ng/mL to produce a non-negative result. Below that level, the test reads negative.

A cutoff is a screening threshold, not a measure of impairment, dose or timing. Two people taking the same medication can produce very different urine concentrations depending on dose, hydration and how long ago they took it. Our drug test cutoff levels guide explains how cutoffs are set and why they differ between panels.

Is BZO Part of a DOT Drug Test?

No. The federally regulated DOT test screens for marijuana, cocaine, amphetamines, opioids and PCP. The initial cutoff table in 49 CFR §40.85 does not include benzodiazepines. BZO appears on non-DOT panels chosen by employers, clinics, courts and treatment programs, most often on 10-panel and larger cups.

How Long Do Benzodiazepines Show Up in Urine?

There is no single detection window for BZO, because the class includes short-acting and long-acting drugs. Short-acting drugs such as alprazolam are usually detectable for a few days after use. Long-acting drugs such as diazepam, and their metabolites, can remain detectable much longer, especially with regular use. Dose, frequency, metabolism and the test’s cutoff all change the result.

For published ranges by drug, the ARUP Consult urine detection windows table is a widely used clinical reference. Treat any detection window as an estimate, not a guarantee.

Which Tests Include a BZO Panel?

BZO is usually not included in basic 5-panel tests. If benzodiazepines matter to your program, confirm that BZO appears in the product’s drug list before ordering.

BZO Cutoffs on Our Urine and Saliva Tests

Urine BZO panels are almost always set at 300 ng/mL. Oral fluid tests use much lower cutoffs because drug concentrations in saliva are lower, and they mainly reflect recent use.

How to Read a BZO Result

• Negative: a control line (C) and a test line (T) next to BZO, even if the T line is faint. Benzodiazepines were not detected at or above the cutoff.
• Non-negative (preliminary positive): a control line with no test line next to BZO. The sample may contain benzodiazepines at or above 300 ng/mL.
• Invalid: no control line. Repeat the test with a new device.

Read the result inside the time window printed in the instructions, usually around 5 minutes. Our guide to reading a drug test cup shows each line pattern with examples.

Preliminary Results and Confirmation Testing

A rapid BZO result is preliminary. Prescribed benzodiazepines are a common, legitimate reason for a non-negative screen, and some non-benzodiazepine medications have been reported to cross-react with certain immunoassays. A non-negative result should be confirmed by a laboratory method such as GC-MS or LC-MS/MS, following your program’s procedure, before any decision is made. Laboratory confirmation identifies the specific drug and concentration, which a rapid screen cannot do.

What to Do After a Non-Negative BZO Result

1. Record the result with the time read, device lot number and expiration date.
2. Treat it as preliminary. The screen cannot tell which benzodiazepine is present or whether it was prescribed.
3. Follow your medication review procedure. Prescriptions are reviewed by a clinician or medical review officer.
4. Send the sample for confirmation by GC-MS or LC-MS/MS, which identifies the specific drug and metabolites.
5. Act on the confirmed result under your written program policy.

Buying BZO Drug Tests in Bulk

Clinics, treatment centers, courts and employers that screen for benzodiazepines usually buy multi-panel cups with BZO already included, plus single-panel BZO dip cards for add-on testing. Request a bulk quote with your panel list and monthly volume, or browse all urine drug test cups.

Frequently Asked Questions

What does BZO stand for on a drug test?

BZO stands for benzodiazepines, a class of prescription sedatives that includes alprazolam, diazepam, lorazepam and clonazepam.

What is the cutoff for BZO on a drug test?

Most rapid urine tests list BZO at 300 ng/mL. Check the package insert for the exact cutoff of the device you are using.

Will Xanax show up as BZO on a drug test?

Alprazolam (Xanax) is a benzodiazepine and is generally detected by the BZO panel when its concentration is at or above the cutoff. Results depend on dose, timing and the specific test.

Can a BZO test miss clonazepam or lorazepam?

Yes. Many rapid immunoassays respond weakly to clonazepam and lorazepam, so they can screen negative at a 300 ng/mL cutoff. Laboratory testing is more reliable for monitoring these drugs.

Is BZO included in a DOT drug test?

No. The DOT drug test does not screen for benzodiazepines. BZO appears on non-DOT panels selected by employers, clinics and treatment programs.

What should happen after a non-negative BZO result?

Treat it as preliminary. Confirm it with a laboratory test such as GC-MS or LC-MS/MS and review prescriptions before making any decision.