What Do the Codes on a Drug Test Mean [2026 Guide]
Medically reviewed by Dr. Matthew Nuesse, Certified Medical & DOT Examiner
One of the most common scenarios when it comes to official drug testing (especially for employment) is: you open your drug test result (or announcement) and see a column of short letter codes.
AMP. BZO. MTD.
Each one sits next to a line or a result, but none of them spell out what they actually screen for. It reads like it was written for someone who already knows the shorthand.
Every code on a drug test is an abbreviation for a substance, or a group of substances that the panel checked, or is going to check. We created a simple guide to help you decipher and understand the tests better.
It starts with the ones people search for most, so you can read your result without guessing.
What do the codes on a drug test mean?
Each code stands for one substance or drug class the test screened for. A code by itself is neutral. It tells you what was looked for, not what was found. Whether something was detected depends on the line or mark next to that code, and even then a screening result is preliminary until a lab confirms it. Here are the six codes people ask about most often.
| Code | Stands for | Class |
|---|---|---|
| BUP | Buprenorphine | Opioid |
| AMP | Amphetamine | Stimulant |
| BZO | Benzodiazepine | Sedative |
| MTD | Methadone | Opioid |
| MOP | Morphine / Opiates | Opioid |
| TCA | Tricyclic antidepressant | Prescription |
What a code on your drug test result actually tells you
A code is the test's label for one assay, meaning one thing it screened for. So, essentially, a drug or group of drugs that are being detected.
On most at-home urine tests, the result works opposite to how people expect. A visible line, even a faint one, usually means the sample tested negative for that code. A missing line means the sample was flagged as preliminary positive.
That catches almost everyone off guard the first time. If you are staring at a faint line and panicking, read our guide on what a faint line on a drug test means before you draw any conclusions.
Then there is that word "preliminary." At-home and instant tests use immunoassay technology, which the NIH's StatPearls clinical reference describes as presumptive rather than definitive. A flagged code points to a possible result that a laboratory method would need to confirm.
You will also see panels advertised as "no THC" or "non-THC." Those skip the marijuana code and screen for everything else. Employers reach for them when cannabis is legal locally, but other substances still matter.
Keep in mind that legal doesn't guarantee an automatic pass, or that the employer will always exclude THC from the test.
The six most common drug test abbreviations, explained
These six codes carry the most confusion, and by extension cause the most anxiety.
Each one screens for a specific class of substance, and several overlap with legal prescriptions. That overlap is where false positives tend to start.
AMP: Amphetamines
AMP screens for amphetamines, the stimulant class that includes prescription medications like Adderall and Vyvanse alongside illicit speed. A legitimate ADHD prescription can trigger this code. So can several unrelated medications.
Clinical reviews have documented selegiline, bupropion, and pseudoephedrine cross-reacting as amphetamines on immunoassay screens. If AMP flags and you take a prescribed stimulant or decongestant, note that before any confirmation step.
BUP: Buprenorphine
Buprenorphine stands under BUP, the opioid used in medication-assisted treatment under brand names like Suboxone and Subutex.
It gets checked separately from general opiates because the standard opiate screen is built to detect morphine and misses structurally different opioids. If you are prescribed buprenorphine, a BUP result is exactly what you would expect to see.
BZO: Benzodiazepines
BZO screens for benzodiazepines, the sedative class covering Xanax, Valium, Klonopin, and Ativan. These rank among the most commonly prescribed medications in the country, so a prescribed anti-anxiety medication will register here. The code says nothing about legality on its own.
Just make sure to provide the prescription documentation to the medical examiner.
MTD: Methadone
Methadone is screened under MTD. It's an opioid used both for chronic pain and for opioid-use-disorder treatment. Methadone gets its own code because, like buprenorphine, it does not reliably show up under the general opiate assay.
People misread this one constantly, usually confusing it with MDMA, which is a completely different substance.
MOP: Morphine and Opiates
MOP screens for morphine and the broader opiate group, including codeine, heroin, and morphine itself. You may see the same assay labeled OPI, or written as OPI300 to note the cutoff level.
MOP and OPI refer to the same thing on most panels. Poppy seeds, eaten in large amounts, are a known source of a preliminary positive here.
TCA: Tricyclic Antidepressants
TCA screens for tricyclic antidepressants, an older class of prescription medication such as amitriptyline and nortriptyline. This is a prescription-only code, and it produces unexpected results often because these drugs and their relatives cross-react on a screen. If TCA flags, see what can cause a false positive drug test for the common culprits.
Alcohol, nicotine, and newer substances
Some codes confuse people because they screen for things that are legal, recently added, or not obviously "drugs" at all.
ETG stands for ethyl glucuronide, a byproduct your body makes after drinking alcohol. It appears on alcohol-specific screens rather than standard drug panels, and it stays detectable in urine longer than alcohol itself, roughly one to two days.
A SAMHSA advisory published by the NIH notes that ETG is sensitive enough to flag incidental exposure from everyday products that contain alcohol, such as mouthwash and hand sanitizer. That sensitivity is why a positive result may not be treated as proof of drinking on its own.
COT stands for cotinine, the marker your body produces from nicotine. It shows up on tobacco and vaping screens, the same category our nicotine urine test checks for.
K2 or SYN flags synthetic cannabinoids, sometimes sold as "spice." These are chemically different from the THC in marijuana and need their own assay.
KRA stands for kratom, a botanical that acts on opioid receptors. Standard opioid codes miss it, so panels that care about it add a dedicated line.
FEN stands for fentanyl. Standard opiate assays do not catch it, so more panels now screen for it separately.
The complete list of drug test abbreviations
Here is every common code in one place. Manufacturers label the same substances slightly differently, so a few appear under more than one abbreviation.
| Code | Stands for | Substance class | Also seen as |
|---|---|---|---|
| AMP | Amphetamine | Stimulants (Adderall, speed) | — |
| mAMP / MET | Methamphetamine | Stimulants | MET, MAMP |
| BAR | Barbiturates | Sedatives | BARB |
| BZO | Benzodiazepines | Sedatives (Xanax, Valium) | BENZ |
| BUP | Buprenorphine | Opioids (Suboxone, Subutex) | — |
| COC | Cocaine | Stimulants | — |
| MOP | Morphine / Opiates | Opioids (codeine, heroin, morphine) | OPI, OPI300 |
| MTD | Methadone | Opioids | — |
| OXY | Oxycodone | Opioids | — |
| FEN / FYL | Fentanyl | Opioids | — |
| MDMA | Ecstasy / Molly | Stimulants | XTC |
| THC | Marijuana / Cannabis | Cannabinoids | — |
| K2 / SYN | Synthetic cannabinoids | Cannabinoids | SPICE |
| KRA | Kratom | Botanical, opioid-like | — |
| PCP | Phencyclidine | Dissociatives | — |
| TCA | Tricyclic antidepressants | Prescription (false-positive risk) | — |
| PPX | Propoxyphene | Opioids | — |
| ETG | Ethyl glucuronide | Alcohol metabolite | ALC |
| COT | Cotinine | Nicotine metabolite | NIC |
Codes vary slightly by manufacturer. The substance class is what matters.
What the colors and lines on a drug test cup mean
Multi-panel cups group their codes into colored bands, and people often assume the colors carry meaning.
They do not.
The banding is a visual way to organize which codes sit where on the cup. Your result comes from the lines.
Each code has a test line (T) and a control line (C). The control line confirms the test ran correctly. The test line reads your sample, and on competitive-immunoassay tests, any visible test line, faint or bold, reads as negative for that substance. Our multi-level home drug test guide walks through reading a full cup line by line.
Preliminary result vs confirmed result
Every code on a home or instant test produces a preliminary result, which is important because it doesn't mean definitive. Screening tests use immunoassay technology, which is fast and accurate for most samples but can cross-react with legal medications and foods.
A confirmed result comes from a laboratory method like GC-MS or LC-MS, which identifies the exact molecule rather than the class. So a preliminary positive on a single code is where the story starts, but it doesn't end there. Anyone testing at home should treat a flagged code as a prompt to look closer.
Drug Test Abbreviations and Codes - FAQ
What does a positive code on a drug test mean?
A positive code means the sample was flagged for that substance class at the screening stage. It is a preliminary result rather than a confirmed one, because immunoassay screens can cross-react with prescriptions and certain foods. A laboratory confirmation test is what turns a preliminary positive into a definitive one.
What is the difference between MOP and OPI on a drug test?
There is essentially no difference. Both codes screen for the opiate group, including morphine, codeine, and heroin. MOP is short for morphine and OPI for opiates, and manufacturers use one or the other for the same assay. You may also see OPI300, which just names the cutoff level the test uses.
What does "no THC" mean on a drug screen?
A "no THC" or non-THC panel screens for every substance in its lineup except marijuana. Employers use these where cannabis is legal locally, but other drugs still matter to them. It does not mean the test is weaker, only that the THC code has been left off the panel.
Can a prescription cause one of these codes to show positive?
Yes, and it happens often. Prescription stimulants can flag AMP, benzodiazepine medications flag BZO, and tricyclic antidepressants flag TCA. This is why a screening result is preliminary. A confirmation test can distinguish a legitimate prescription from an illicit substance.
What does ETG stand for on an alcohol test?
ETG stands for ethyl glucuronide, a byproduct your body produces after processing alcohol. It appears on alcohol-specific screens rather than standard drug panels, and it stays measurable in urine for roughly one to two days after drinking, longer than alcohol itself.
Are the codes the same on every drug test?
The core codes are consistent, but manufacturers vary the exact letters. Morphine may appear as MOP or OPI, methamphetamine as MET or mAMP, benzodiazepines as BZO or BENZ. The substance class behind the code stays constant, so match the class rather than memorizing every letter combination.
The bottom line on reading your codes
Once you know that a code is just a label for what the drug test is looking for, the whole result will stop feeling like an (anxiety-inducing) puzzle. Match each abbreviation to its substance class, remember that a visible line usually reads negative on these tests, and treat any flagged code as preliminary until a lab confirms it.
Prescriptions and everyday foods set off more of these codes than people realize, so a single positive is rarely the full picture.
Still working out whether a substance will clear in time? Our THC Detection Calculator estimates THC detection windows based on your own usage, and our multi-level THC test lets you check where you stand at home before it counts.
Medically reviewed by:
Dr. Matthew Nuesse, DC, Certified Medical & DOT Examiner
Dr. Nuesse is a certified medical examiner and DOT-qualified provider with over a decade of experience in occupational health and drug screening. He reviews Exploro's content for clinical accuracy.
Written by:
Andrej Dugandžić
Andrej is a writer and editor at Exploro and a modern medical device enthusiast with a background in chemical engineering. Through research, he brings light to topics like at-home drug testing, substance detection, detox truths and myths, and many more.
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