A toxicology screen tests for a defined list of drugs and their byproducts in your body, typically using urine, blood, or saliva. The most common version, the standard 5-panel test, checks for five drug classes: marijuana (THC), cocaine, amphetamines, opioids, and phencyclidine (PCP). Broader panels and hospital screens expand that list significantly depending on the situation.
The Standard 5-Panel Test
The 5-panel drug test is the baseline for most federal workplace and Department of Transportation testing. It covers five categories, but each category breaks down into multiple specific substances. Under amphetamines, the test checks for amphetamine, methamphetamine, MDMA (ecstasy), and MDA. Under opioids, it screens for codeine, morphine, heroin (detected as 6-acetylmorphine), hydrocodone, hydromorphone, oxycodone, and oxymorphone. That means common prescription painkillers like Vicodin, OxyContin, and Dilaudid are all covered under a standard 5-panel screen.
As of January 2025, federal guidelines from the Department of Health and Human Services also added fentanyl to the authorized testing panel, reflecting its role in the current overdose crisis. This makes the “5-panel” label slightly misleading since it now captures well over a dozen individual substances across those five categories.
Extended 10-Panel and 14-Panel Tests
Employers, courts, and treatment programs often use expanded panels. A 10-panel test typically adds benzodiazepines (Xanax, Valium, Ativan), barbiturates, and methadone to the standard five categories. A 14-panel test goes further, adding substances like buprenorphine (used in opioid addiction treatment), tricyclic antidepressants, EDDP (a methadone byproduct that confirms someone actually took methadone rather than spiking their sample), and oxycodone as a separate line item with its own detection threshold.
Which panel you’re given depends entirely on who ordered the test. Pre-employment screens for office jobs often stick with 5 panels. Probation, pain management clinics, and substance abuse programs tend to use 10- to 14-panel tests to capture a wider range of prescription and illicit drugs.
Hospital and Emergency Room Screens
Toxicology screens ordered in a medical setting look different from workplace tests because they serve a different purpose. Doctors aren’t checking for policy violations; they need to identify what’s causing your symptoms so they can treat you safely.
A hospital urine screen typically covers the same five core drug classes: cocaine, amphetamines, marijuana, PCP, and opioids, with many also including benzodiazepines. But emergency departments also run blood (serum) tests that target a separate group of substances: acetaminophen (Tylenol), aspirin and other salicylates, and alcohol. Extended blood panels may add tricyclic antidepressants and barbiturates. Acetaminophen and aspirin are included because overdoses of these common medications can cause severe organ damage that’s treatable if caught early, even when a patient can’t communicate what they took.
How the Testing Process Works
Toxicology screening happens in two stages. The first is an immunoassay, a rapid chemical test that flags samples above a set concentration threshold. For marijuana on a urine test, that initial cutoff is 50 nanograms per milliliter. For fentanyl, it’s just 1 nanogram per milliliter, reflecting how potent the drug is and how little ends up in your system.
If the initial screen comes back positive, a second confirmatory test is run using mass spectrometry, a much more precise technology that identifies the exact molecules present. This step exists because immunoassays are prone to false positives and can’t always distinguish between chemically similar substances. Mass spectrometry produces far fewer false results and can identify specific drugs rather than just drug families. A result isn’t considered confirmed positive until it passes both stages.
Urine, Blood, Saliva, and Hair
Urine is the most common specimen type for drug screening. It offers a practical detection window: a single dose of most drugs is detectable for 1.5 to 4 days, while chronic use extends that to roughly a week. Heavy marijuana and cocaine users can test positive even longer. Urine is also easy to collect and works well with both immunoassay and mass spectrometry methods.
Blood testing detects most substances for only 1 to 2 days, making it useful when doctors need to know what’s in your system right now, such as in an emergency room. Oral fluid (saliva) testing has the shortest window, typically 5 to 48 hours, but it’s harder to tamper with and is increasingly used in workplace settings. Federal guidelines now authorize oral fluid testing alongside urine, with adjusted cutoff levels to account for the lower drug concentrations found in saliva.
Hair testing covers the longest window, potentially detecting drug use from months earlier, but it isn’t part of standard federal or emergency panels. It’s mostly used in specialized forensic or legal contexts.
What Can Cause a False Positive
One of the most common concerns about toxicology screens is whether everyday medications can trigger a positive result. The answer is yes, at least on the initial immunoassay. False positives for amphetamines and methamphetamine are the most frequently reported, but false flags for opioids, PCP, benzodiazepines, barbiturates, cannabinoids, and methadone also occur.
Specific medications known to cause false positives include ibuprofen, naproxen, diphenhydramine (Benadryl), dextromethorphan (a cough suppressant), bupropion (Wellbutrin), sertraline (Zoloft), trazodone, venlafaxine (Effexor), quetiapine (Seroquel), ranitidine (Zantac), and certain antibiotics in the quinolone family. Even over-the-counter nasal inhalers containing levmetamfetamine can trigger an amphetamine positive.
This is exactly why confirmatory testing exists. If you’re taking any prescription or over-the-counter medication, disclosing it before or after a test allows the reviewing officer or physician to interpret results correctly. A confirmed positive using mass spectrometry is far more reliable than the initial screen alone, since it can distinguish the actual drug molecules from chemically similar compounds in other medications.