Most drug tests screen for five core substances: marijuana (THC), cocaine, amphetamines, opiates, and phencyclidine (PCP). This standard 5-panel test is the baseline for federal workplace screening, including all Department of Transportation testing. Depending on your employer, the court system, or the specific situation, you may face an expanded panel that adds prescription drug classes to the list.
The Standard 5-Panel Test
The five drug classes in a basic screen have remained the same for years. They are:
- Marijuana (THC): The test detects a metabolite your body produces after processing THC, not THC itself. This is why marijuana can show up days or weeks after use, long after any effects have worn off.
- Cocaine: Detected through its primary metabolite, benzoylecgonine, which lingers in the body longer than cocaine does.
- Amphetamines: Covers methamphetamine, amphetamine, and in the federal panel, MDMA (ecstasy) and its metabolite MDA.
- Opiates: Targets codeine, morphine, and heroin (detected as a unique metabolite called 6-acetylmorphine).
- PCP (phencyclidine): Sometimes called angel dust, still included despite relatively low rates of use.
This is the panel used for federal employees, commercial truck drivers, pilots, railroad workers, and many private employers who follow federal guidelines.
What Expanded Panels Add
A 10-panel test keeps everything from the 5-panel and adds several prescription drug categories. The typical additions include benzodiazepines (Xanax, Valium, Ativan, Klonopin), barbiturates, expanded opioids (oxycodone, hydrocodone, fentanyl), and sometimes methadone or propoxyphene. Some panels also screen for methaqualone.
Employers in healthcare, law enforcement, and government positions frequently use 10-panel or 12-panel tests. Court-ordered testing often uses expanded panels as well, sometimes adding alcohol metabolites. The exact substances vary by provider and purpose, so there is no single universal 10-panel formula.
One notable upcoming change: the Department of Transportation proposed adding fentanyl to its standard testing panel in September 2025, with implementation expected in early 2026. This would be the most significant expansion of DOT drug testing in years, reflecting the scale of fentanyl’s role in overdose deaths.
How the Testing Process Works
Drug tests use a two-step process. The first step is an immunoassay, a quick chemical reaction that flags samples as either positive or negative. It’s fast and relatively cheap, which is why it’s used for the initial screen. But immunoassays can produce false positives because they react to substances with similar chemical structures, not just the target drug.
If your initial screen comes back positive, the sample goes through a second, more precise test using a technology called mass spectrometry. This confirmatory step identifies the exact molecules present in the sample and their concentration. It’s far more accurate and essentially eliminates false positives. You won’t be reported as positive based on the initial screen alone.
Detection Cutoff Levels
Drug tests don’t simply detect “any trace” of a substance. Each drug has a concentration threshold, measured in nanograms per milliliter, that the sample must exceed to count as positive. For a urine test under federal guidelines, the initial screening cutoff for marijuana metabolites is 50 ng/mL, dropping to 15 ng/mL at the confirmatory stage. Cocaine’s initial cutoff is 150 ng/mL (confirmed at 100 ng/mL). Amphetamines are set at 500 ng/mL initially, confirmed at 250 ng/mL. Opiates (codeine and morphine) have a relatively high initial cutoff of 2,000 ng/mL.
Oral fluid (saliva) tests use much lower thresholds because drug concentrations in saliva are naturally lower. Marijuana’s initial oral fluid cutoff is just 4 ng/mL, and cocaine’s is 15 ng/mL. These aren’t numbers you need to memorize, but they explain why the same drug can produce different results on different test types.
How Long Drugs Stay Detectable
Detection windows vary dramatically by the type of specimen collected and how frequently you’ve used a substance. In urine, a single dose of most drugs is detectable for roughly 1.5 to 4 days. Chronic users face longer windows, typically about a week after last use. Heavy, long-term marijuana and cocaine users can test positive for even longer than that.
Blood and plasma have the shortest detection windows, usually just 1 to 2 days. Oral fluid falls between blood and urine, with most substances detectable for 5 to 48 hours. Hair testing has the longest window by far, often reaching back 90 days, because drug metabolites become trapped in the hair shaft as it grows.
The type of test you face depends on the situation. Urine remains the most common for employment screening. Oral fluid testing is growing in popularity because it’s harder to tamper with and the federal government recently authorized it for workplace programs. Hair tests are less common but used when employers want to assess longer-term use patterns.
Specimen Validity Checks
Labs don’t just test for drugs. They also check whether your sample is actually legitimate. Every urine specimen is evaluated for creatinine concentration, which indicates whether the sample has been diluted with water. If creatinine is unusually low, the lab measures specific gravity as a second check. The sample’s pH is also tested, since normal urine falls within a predictable range and values outside that range suggest tampering.
Labs also screen for oxidizing adulterants, chemicals that some people add to urine samples in an attempt to destroy drug metabolites. If the sample looks, smells, or behaves abnormally during testing, additional validity checks are triggered. A specimen flagged as substituted or adulterated is treated as a refusal to test under federal rules, which carries the same consequences as a positive result.
False Positives and Prescription Medications
Certain legal medications can trigger a positive result on the initial immunoassay screen. Some common culprits include certain antidepressants that can flag for amphetamines, and over-the-counter cold medications containing pseudoephedrine. Poppy seeds, while often treated as a joke, genuinely can cause a positive result for opiates at high enough quantities.
This is where the confirmatory test and the Medical Review Officer (MRO) become important. If your confirmatory test is positive, an MRO (a licensed physician trained in drug testing) reviews the result before it’s reported to your employer. The MRO will contact you and ask whether you have a valid prescription or medical explanation. If you have a legitimate prescription for a medication that caused the positive, the MRO typically reports the result as negative.
Your medical information is protected during this process. Under federal rules, individual test results and medical details cannot be released to third parties without your written consent. The main exception is when the MRO determines that a medication or medical condition poses a significant safety risk in a safety-sensitive job, in which case they can notify the employer through a separate communication, not on the standard test form.
Types of Drug Tests by Situation
Pre-employment screening is the most common scenario, typically using a 5-panel urine test. Random testing occurs in federally regulated industries like transportation, where workers can be selected without warning at any point during employment. Post-accident testing is required in many workplaces after a safety incident, and reasonable suspicion testing happens when a supervisor observes signs of impairment.
Court-ordered and probation testing tends to be more frequent and may use expanded panels or multiple specimen types. Athletic drug testing follows entirely different protocols and screens for performance-enhancing substances that workplace tests ignore. Each context determines not just what’s tested but how often and with what consequences.