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Blood Test Tracker

Urine Benzodiazepines Screen

A urine screen for benzodiazepines, a family of sedatives such as diazepam. It can miss some of them, and a positive is presumptive until confirmed.

AI-verified against cited sources. Awaiting expert reviewAlso called BENZO, BZOLOINC 3390-2

What it is

Benzodiazepines are prescription medicines used for anxiety, seizures, insomnia, alcohol withdrawal and sedation before procedures. The urine screen uses a quick test, called an immunoassay, built to react to common breakdown products such as oxazepam and nordiazepam. It reports only positive or negative against a set cutoff, often 200 or 300 ng/mL, though some kits use lower levels. It can't tell which benzodiazepine you took, how much, or exactly when.

Why it matters

Clinicians order this screen when checking for causes of sleepiness or confusion, for other drugs taken together, or to see whether a prescribed benzodiazepine is being taken. The screen has real blind spots. Some benzodiazepines, such as clonazepam, lorazepam and alprazolam, are missed by many kits, so a negative result does not prove none was taken. Confirmation tests list individual drugs.

If it’s high

A positive screen means the test reacted at or above the lab's cutoff. That is expected if you take a prescribed benzodiazepine. Other medicines can also cause a positive reading. A confirmation test on the same sample can tell which benzodiazepine is present.

Common causes

  • A prescribed benzodiazepine taken as directed
  • A medicine that cross-reacts with the test, such as naproxen
  • A benzodiazepine that was not prescribed

What can help

  • Tell the clinician and the lab about every prescription, over-the-counter medicine and supplement you take
  • Ask whether the result was confirmed with a second test that names the specific drug
  • Ask whether a more specific test is needed if the screen result doesn't match your medicine list

What can affect your result

  • The cutoff the lab uses (200 or 300 ng/mL are common, and some kits use lower)
  • Which benzodiazepine it is: many kits detect oxazepam-type breakdown products well and detect clonazepam, lorazepam, midazolam and alprazolam poorly
  • How long ago the dose was taken
  • How dilute the urine is
  • Prescription and over-the-counter medicines
  • Prescribed benzodiazepines can give a positive screen, although some are missed (see below).
  • Many screening kits miss some benzodiazepines, including clonazepam, lorazepam, midazolam and alprazolam, so a negative screen does not rule out use.
  • Naproxen has been reported to cause a false-positive benzodiazepine screen.
  • Very dilute urine can push a low level under the cutoff and give a negative result.
  • Each lab sets its own cutoff, and kits differ in which benzodiazepines they react to.

Any time. A random urine sample is typical. When results will be used for work or legal reasons, the collection may be observed and the sample temperature checked. Shows recent use. For most drugs, urine tests can detect use from roughly 1 to 4 days earlier, depending on the drug, the dose and how often it was taken.

When to talk to a clinician

A positive screen alone is not an emergency. Call 911 or your local emergency number if someone is extremely sleepy or can't be woken, is breathing slowly or shallowly, or is confused after taking a sedative, especially together with alcohol or opioids. In the US, Poison Control is 1-800-222-1222.

Questions you could ask

  • Does this screen detect the benzodiazepine I take, or could it miss it?
  • Who will see this result, and how will it be used?
  • Could one of my medicines explain this result?
  • Was this result confirmed with a test that names the specific drug?
  • What cutoff did this lab use?

Questions people ask

I take clonazepam, lorazepam or alprazolam, and my screen was negative. Why?

Many urine screening kits don't react well to these drugs. A negative screen doesn't prove none was taken. If it matters for your care, ask whether a more specific test that names individual benzodiazepines can be done.

Will my prescribed benzodiazepine show up?

Often, but not always. Diazepam breaks down into products the screen is built to find. Some others are missed by many kits. Tell the clinician and the lab what you take.

Can a common pain reliever cause a false positive?

Naproxen has been reported to cause a positive benzodiazepine screen. A confirmation test on the same sample can tell a false positive from a true one.

Show the science and sources

For clinicians and researchers

Benzodiazepine immunoassays use oxazepam or nordiazepam as positive controls (Labcorp) and mostly detect benzodiazepines that are metabolized to oxazepam glucuronide. Clonazepam, lorazepam, midazolam and alprazolam are missed by many urine screens (StatPearls, Benzodiazepine Toxicity). Labcorp states that positives are usually above 300 ng/mL of urine metabolites and should be confirmed by a second technique, and its screen covers alpha-hydroxyalprazolam, diazepam, nordiazepam and oxazepam. LOINC has screen codes for 200 and 300 ng/mL, and a hospital device reported in 2025 used 150 ng/mL. Mayo Clinic Laboratories uses an LC-MS/MS targeted benzodiazepine screen with a 10 ng/mL cutoff for most parent drugs and 50 ng/mL for several glucuronides, reported as not detected or present. Naproxen is the Merck Manual's example of a cross-reacting drug on the benzodiazepine screen. Immunoassay positives are presumptive until a second independent method confirms them (Saitman 2014). A positive screen indicates recent exposure, but does not confirm causality in acute toxicity or name the specific agent (StatPearls). Urine testing cannot determine the amount or frequency of use (Merck Manual).

LOINC 3390-2 (primary), 14316-4, 70141-7, 70142-5. Specimen: urine.

Sources

  1. Drug Testing, Merck Manual Professional Version (2026)
  2. Drug Testing, MedlinePlus (National Library of Medicine)
  3. Commonly prescribed medications and potential false-positive urine drug screens, American Journal of Health-System Pharmacy (2010)
  4. False-positive interferences of common urine drug screen immunoassays: a review, Journal of Analytical Toxicology (2014)
  5. Abnormal Urine Drug Screens in Pregnancy: Opportunity for Laboratory Stewardship, EJIFCC (IFCC) (2025)
  6. Benzodiazepines, Screen and Confirmation, Urine (test 074427), Labcorp
  7. TBSU: Targeted Benzodiazepine Screen, Random, Urine, Mayo Clinic Laboratories Extended Catalog
  8. Benzodiazepine Toxicity, StatPearls Publishing (NCBI Bookshelf) (2023)
  9. Contact us - Poison Control, Poison Control (America's Poison Centers)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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