Urine Toxicology Screen
Case: you are seeing a 30-year-old patient with a new diagnosis of ADHD, and their psychiatrist recommended starting a stimulant medication (to be managed by you - the primary care provider). They have a history of cocaine use (in remission). You think about performing a urine toxicology screen prior to starting a stimulant.
What is a urine toxicology screen? (also referred to as “urine drug test” or “urine drug screen”) It is a common test used to screen for medication use, medication misuse, and drug use. It is used in the clinical setting for many purposes. Some examples:
Used to screen high risk patients prior to starting a stimulant medication (e.g. if there is a history of substance use disorder, or any reason to suspect drug abuse or drug-seeking behaviour) (1)
Used prior to initiating opioid agonist treatment (2)
To monitor adherence and response to opioid agonist treatment and check for ongoing illicit substance use (2)
Used to screen for substance misuse if suspected (i.e. if you have a moderate to high pre-test probability)
In the mental health setting, for the purpose of identifying substance use that may contribute to current psychiatric disease (3)
Pain management programs prior to starting certain pain medications (e.g. opioids) (3)
Concern for drug exposure (e.g. accidental exposure in a pediatric patient)
For legal or forensic purposes (e.g. forensic psychiatry patients)
You might assume that simply detecting the presence or absence of a substance in the results is enough to provide clarity—but it's not that simple. When ordering this test, we must consider our pretest probability (i.e., level of suspicion for drug use or exposure), the purpose of the test, and the likelihood of false-positive or false-negative results.
What drugs are included in a urine toxicology screen? It varies depending on where you work.
In Canada: common drugs tested include amphetamine, cocaine, benzodiazepines, marijuana, opioids, methadone and ethanol (alcohol)
In the US: the basic test includes amphetamine, cocaine, marijuana, opioids, and phencyclidine; the tests vary by medical facility and region - so check with your local labs (3).
I work in London Ontario in a community setting, so I look up local lab information for what is tested in the urine toxicology screen. For example at Dynacare, they offer a broad spectrum urine toxicology screen that tests for several drugs. This is helpful because I know what will be screened before I order the test.
BOTTOM LINE: we must consider our pretest probability, the purpose of the urine toxicology screen, and the likelihood of false-positive or false-negative results before ordering this test.
How accurate is a urine toxicology screen?
Immunoassays are the most widely used method, commonly used for initial screening. They can give false-positive and false-negative results (4). Immunoassays may not distinguish between or detect all members within a single class of medications and may not detect synthetic/semi-synthetic substances (5). This is often a point of care urine drug test.
Liquid chromatography or gas chromatography–mass spectrometry offers a highly sensitive and specific technique for detecting drugs or metabolites (3), but takes longer to process. Many labs refer to this as the broad spectrum toxicology screen.
What should I assess for before ordering a urine toxicology screen?
Make sure you have a good indication to order it in the first place (see list above).
Always ask for patient consent when ordering a urine drug screen, and explain the rationale as to why you are ordering it. I always like to use open language and clearly explain to the patient why I’m order a urine drug screen - often it’s to make sure you can safely prescribe a medication.
Screen for substance use (e.g. nicotine, marijuana) past and present. If currently using substances, clarify the last time it was used.
Screen for mental health symptoms/concerns.
Current medication list, including over the counter items.
This will help with interpreting the results - do they make sense based on the history, or not?
What is the window of detection for substances? the window that drugs are detected in the urine depends on several factors, including the half-life of drugs and metabolites, lipophilicity, and depends on the amount ingested and whether the drug use is occasional or constant (1). Typical drug detection windows are listed below but vary in the literature (5):
Window of detection for common drugs in the urine toxicology screen:
opiates: 2-5 days (*depends on the type and short vs. chronic use)
methadone: up to 6 days
short acting benzodiazepines: 1-2 days
long acting benzodiazepines: up to 30 days
cocaine/metabolites: 2–3 days
THC single use: 1–3 days
THC habitual use: up to 30 days
methamphetamine: 2–5 days
alcohol: 6–24 hours
phencyclidine (PCP): 5-6 days
BOTTOM LINE: if you order an immunoassay urine tox screen - there is a higher risk of false positive and negative results. This is often used as an initial screening test. Chematography (broad spectrum urine toxicology screen) offers higher sensitivity and specificity.
Back to the case: given the patient’s history of cocaine use, you perform a review of systems to screen for ongoing drug use, mental health symptoms, current medications and over the counter products. They take an antidepressant, benzodiazepine as needed, and they smoke cigarettes. They report using marijuana daily. You order a broad spectrum urine toxicology panel. You include on the requisition that the patient takes benzodiazepines, uses nicotine and marijuana, and that you are screening for drug use prior to starting a stimulant medication.
RESULTS: (the lab only reports which drugs were detected)
How do we interpret the results?
Amphetamines: DETECTED — not reported in the history
Aminoclonazepam: DETECTED — makes sense from the history
Cotinine: DETECTED — metabolite of nicotine, makes sense from the history
Sertraline: DETECTED — makes sense from the history
THCA: DETECTED —makes sense from the history
During a follow up visit, you review the results with the patient. They share that they’ve been using a friend’s prescription stimulant (lisdexamphetamine, commonly known as Vyvanse) over the past month to manage their ADHD symptoms. This opens the door for an important conversation about the risks of misusing prescription medications and the dangers of taking medications not prescribed to you.
Together, you discuss the potential benefits and risks of starting a prescribed stimulant for ADHD, emphasizing the need for close monitoring and responsible use. If a prescription is initiated, clear guidance is given on safe use, and you stress that medications must never be shared with others.
TIP: to interpret the urine toxicology screen, most labs will have information on what they test for. For example, I use the Dynacare Toxicology Interpretation resource and it’s very handy!
ReferencesUrine Drug Testing. The Centre for Addiction and Mental Health (CAMH). N.d. [cited 2025 Jun 5]. Available from: https://www.camh.ca/en/professionals/treating-conditions-and-disorders/opioid-use/opioid-use-assessment/urine-drug-testingCanadian Attention Deficit Hyperactivity Disorder Resource Alliance (CADDRA). Canadian ADHD Practice Guidelines [Internet]. 3rd ed. Toronto: CADDRA; 2011 [cited 2025 Jun 6]. Available from: https://caddra.ca/pdfs/caddraGuidelines2011.pdfUrine drug testing. In: UpToDate, Schwartz, E., Ganetsky, M. (Ed), UpToDate, Hoffman R.J. [Accessed 2025 Jun 6]. Available from: https://www.uptodate.com/contents/urine-drug-testingKale, N. (2019). Urine drug tests: Ordering and interpretation. Am Fam Physician. 99(1):33-39. Available from https://www.aafp.org/pubs/afp/issues/2019/0101/p33.htmlInterpreting urine drug tests (UDT). [Internet]. Provincial Health Services Authority Child Health BC. 2023. [cited 2025 Jun 6]. Available from https://www.childhealthbc.ca/mhsu/interpreting_urine_%20drug_tests/printfileAppendix A - Broad Spectrum Toxicology Screen Interpretation Guide. Dynacare. 2025. [Accessed 2025 Jun 6]. Available from https://www.dynacare.ca/DYN/media/DYN/Pdf/Toxicology-Interpretation-Eng.pdf