A standard urine drug test screens for five classes of drugs: marijuana, cocaine, opioids, amphetamines, and phencyclidine (PCP). This five-panel format is the baseline required for federal workplace testing and Department of Transportation (DOT) regulated employees like truck drivers and pilots. Private employers, courts, and healthcare providers may use expanded panels that check for additional substances.
The Five Drug Classes on a Standard Panel
Each of the five categories covers more than just one substance. Here’s what falls under each:
- Marijuana (THC): Detects the main metabolite your body produces after using cannabis in any form, including edibles, vapes, and flower.
- Cocaine: Picks up benzoylecgonine, the breakdown product of cocaine, including crack cocaine.
- Opioids: Screens for codeine, morphine, heroin (via its unique metabolite 6-acetylmorphine), hydrocodone, hydromorphone, oxycodone, and oxymorphone. Federal guidelines now also include fentanyl, which was added to the mandatory panel because standard opiate screening often missed it entirely.
- Amphetamines: Covers amphetamine, methamphetamine, MDMA (ecstasy), and MDA.
- Phencyclidine (PCP): Detects PCP, sometimes called angel dust.
One important detail: the “opioids” category on older panels frequently missed synthetic and semi-synthetic opioids like fentanyl, oxycodone, and methadone. Standard immunoassay screens are designed to detect natural opiates (morphine, codeine) and often fail to pick up synthetics unless separate tests are specifically ordered. The updated 2025 federal guidelines now require fentanyl testing at a very low cutoff of just 1 ng/mL, reflecting how widespread fentanyl has become.
What Expanded Panels Add
Many employers, courts, and treatment programs use 7-panel, 10-panel, or even 12-panel tests. These add some combination of the following to the standard five:
- Benzodiazepines: Includes Valium, Xanax, Klonopin, and Ativan.
- Barbiturates: Older sedatives like phenobarbital.
- Methadone: Tested separately because it doesn’t trigger a positive on standard opiate screens.
- Propoxyphene: A now-discontinued painkiller still included on some legacy panels.
- Methaqualone (Quaaludes): Rarely encountered but still part of some 10-panel configurations.
If you’re being tested for a job, your employer typically tells you (or the testing facility will tell you) which panel is being used. DOT-regulated tests are locked to the five-class panel by federal law, and labs are not allowed to test DOT specimens for anything beyond those five categories.
How Long Each Substance Stays Detectable
Detection windows vary based on how often you use a substance, your metabolism, body fat percentage, and hydration level. These are general ranges for urine:
- Marijuana: 1 to 3 days after a single use. If you use three times a week, roughly 2 weeks. Daily heavy use can stay detectable for 4 to 6 weeks, and in extreme cases up to 12 weeks. THC is stored in fat tissue, which is why it lingers far longer than other drugs.
- Cocaine: 2 to 4 days for occasional use. Heavy use extends detection to 10 to 22 days.
- Opioids (heroin, codeine, morphine): 1 to 3 days.
- Amphetamines and methamphetamine: 1 to 3 days.
- Fentanyl: 2 to 3 days.
- PCP: Typically 1 to 2 weeks for moderate use, potentially longer with heavy use.
How the Testing Process Works
Urine drug testing happens in two stages. The first is a rapid screening test called an immunoassay, which uses antibodies to detect broad drug classes. Results come back in under an hour, and these are considered presumptive, not definitive. Immunoassays are designed to cast a wide net: they identify that something in a drug class is present but can’t tell you exactly which substance triggered the result.
If the initial screen comes back positive, the sample goes to a second, more precise test. This confirmatory step uses mass spectrometry, a technology that identifies the exact drug and its specific metabolites. It has much lower detection limits and is far less prone to errors. Confirmatory testing typically takes up to three days. A result is only reported as positive after passing both stages, which is why the system catches most false alarms before they reach your employer.
Each drug has a specific concentration threshold (measured in nanograms per milliliter) that must be exceeded for a positive result. For marijuana, the initial screening cutoff is 50 ng/mL, dropping to 15 ng/mL on confirmation. Cocaine’s initial cutoff is 150 ng/mL. Amphetamines are screened at 500 ng/mL. These thresholds exist to filter out trace-level or incidental exposure and focus on actual use.
What Can Trigger a False Positive
Several common medications and supplements can cause the initial immunoassay screen to flag positive even when you haven’t used illegal drugs. This is one of the main reasons confirmatory testing exists.
For amphetamines, the list of potential triggers is long: pseudoephedrine (found in many cold medicines like Sudafed), the antidepressants bupropion and trazodone, the ADHD medication methylphenidate, the weight-loss drug phentermine, and the anti-nausea medication promethazine can all cross-react on the initial screen.
For opiates, over-the-counter cough suppressants containing dextromethorphan, the antihistamine diphenhydramine (Benadryl), and even poppy seeds have caused false positives. The poppy seed issue is real enough that the federal opiate cutoff for codeine and morphine was set at 2,000 ng/mL specifically to reduce false positives from food containing poppy seeds.
For PCP, dextromethorphan shows up again, along with diphenhydramine, the antidepressant venlafaxine, the pain medication tramadol, and ketamine. For marijuana, false positives are less common but have been reported with ibuprofen and certain HIV and heartburn medications.
If you take any prescription or over-the-counter medication regularly, you’ll typically have the chance to disclose this to a Medical Review Officer (MRO) before a positive result is finalized. The MRO reviews your medical history and prescriptions to determine whether a positive result has a legitimate medical explanation.
Validity Testing on Your Sample
Labs don’t just test for drugs. They also check whether the urine sample itself is genuine. Every specimen undergoes validity testing that measures three things: creatinine concentration, specific gravity, and pH.
A specimen with creatinine below 2 mg/dL and specific gravity at or below 1.0010 is flagged as “substituted,” meaning the lab believes it isn’t actually human urine (or has been replaced with water or another liquid). A specimen with creatinine between 2 and 20 mg/dL and specific gravity between 1.0010 and 1.0030 is reported as “dilute,” which can happen from drinking excessive amounts of water before the test. A dilute result may require you to retest. Specimens with a pH below 3 or at 11 or above are flagged as “adulterated,” since normal urine never reaches those extremes without chemical tampering.
For DOT tests, the collector also checks the temperature of your specimen within four minutes of collection. It must fall between 90 and 100°F. A temperature outside that range raises suspicion that the sample was substituted or altered, and you’ll be asked to provide a new specimen under direct observation.