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Urine Drug Testing: Detection Times And More

John Schaffer, LPCC

Medically reviewed by

John Schaffer, LPCC

March 7, 2019

Urine drug testing (also referred to as urinalysis) is considered the gold standard for detecting substances of abuse. The most common urinalysis is simple to administer, quick, and relatively inexpensive.

Urine tests are used in a variety of settings, including employment, probationary, court, and even for home purposes. Many substances are detectable in urine for a specific amount of time, but that time frame may be altered depending on a number of factors.

Urine drug tests test for more than just the substance ingested. This is because the body breaks these substances into smaller pieces, known as metabolites, and excretes them in urine. If a person tests positive for these metabolites, it is a good indication that they took the substance in question.

Different Types Of Urine Drug Testing

The common urine drug screen is clinically referred to as immunoassay screening. The immunoassay test can screen for many different substances and metabolites, and if the results are positive, it is recommended that the sample is sent to a laboratory to confirm results. The urine screen usually needs to be confirmed with laboratory testing if it will be used in legal, probationary, employment, or academic settings.

The tests performed at the lab are either a gas chromatography/mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS). These tests are standard for confirming positive results in immunoassay screening (urine drug test). This type of testing can identify specific substances and amounts of substances in the sample.

Assessments of GC-MS tests need to be conducted in a laboratory setting by highly trained individuals. This is a time-consuming and expensive process, which is why it is usually reserved for confirming a positive urine drug test.

Reasons For Urine Drug Testing

There are many situations where a urine drug screen may be important and possibly even necessary. For instance:

  • In an emergency room setting where a person is exhibiting unusual or potentially violent behavior.
  • Pain management facilities test for the medications they prescribe as well as making sure the patient is not taking additional medications.
  • Before an employer commits to hiring a potential employee.
  • In a position where a person is responsible for operating heavy machinery or performing medical procedures.
  • As part of a substance abuse treatment facility to ensure maintained sobriety.
  • A requirement of probation for an offense that includes alcohol or drug misuse.
  • Part of a court order that mandates sobriety.

In addition to the situations listed above, urine drug screens can also be used if a person is suspected to be misusing drugs or alcohol in a variety of settings, including at home. Some types of urine drug screens are available over-the-counter and test for many different substances.

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Advantages Of Urine Drug Tests

Urine drug tests are the easiest and most affordable form of substance use detection. They are extremely flexible and can be administered almost anywhere any time, and immunoassays usually give immediate results. They do not require a scheduled appointment with a medical professional to be administered, and can even be taken in the privacy of your own home.

Additionally, urine drug tests can be customized to detect specific substances, in practically every combination, with adjustable detection level cut-offs. This is a significant advantage, as testing for specific metabolites can establish past drug use.

If a test result is positive, the urine sample tends to be large enough to retest and still be sent to the lab where the result can be confirmed.

Disadvantages Of Urine Drug Tests

Although not as invasive as other drug screen methods, the urine drug test is still generally intrusive. If the collection facility is off-site, traveling, and the potential of not being able to provide a sample (whether physically unable to urinate or feeling uncomfortable with being observed) could make the process less than ideal.

There is also the possibility that the urine drug test may not detect drug use in the time frame immediately before the sample is taken.

The biggest disadvantage of using a urine drug test is that if the sample is not taken under observation, there is a risk of sample tampering. Many testing containers have tests to measure for sample tampering and are caught quickly. The most common forms of tampering include:


Substitution occurs when a person gives a urine sample that did not come from their body. There are concentrates, liquids, powders, and synthetic urine that are used to pass a urine drug screen. Providing urine from another person has been another method of substitution. People often use hand warmers or other methods to keep the substituted sample warm to avoid being detected.


A diluted sample is urine that has more water than an average sample. This is usually unintentional, and the person typically has just consumed an excess of liquids. Diluting a sample intentionally consists of adding water directly to the sample before turning the sample in.


Adding chemicals to a sample is another common form of sample tampering, known as adulteration. People have been caught putting soap, bleach, eye drops, and even salt in samples in an attempt to pass a urine drug screen. Ingesting large amounts of vinegar has also been observed, however, the amount needed to affect a drug screen would also cause violent diarrhea.

Factors That Can Affect Results Of A Urinalysis

Individual factors can affect the results of a urine drug test. Factors such as age, natural metabolism rate, and body mass are factors outside a person’s control that may affect test outcomes.

Purposely ingesting supplements intended to detox and flush drugs out of a person’s system can alter results, but quite often, it will also modify the sample enough to show in the results that it has been tampered with in some way. This will invalidate the test.

There are several medications that can result in a false positive. This occurs when a urine drug test has a positive result for a substance that the person has not taken. Some of these medications include:

  • selegiline: false positive for amphetamine and methamphetamine
  • Vicks Inhaler: false positive for amphetamine and methamphetamine
  • NSAIDs: (such as ibuprofen, naproxen) false positives for barbiturates and cannabinoid
  • oxaprozin: false positive for benzodiazepines
  • fluoroquinolone: false positive for opioids
  • rifampin: false positive for opioids
  • venlafaxine: false positive for phencyclidine (PCP)

Poppy seeds have also been observed to affect false positive results in urine drug screens for opioids.

Drugs Of Abuse That Urinalysis Can Detect And Timelines

Urine drug tests look for parent drugs and metabolites. As the body breaks down substances, they metabolize (change) into different chemicals. Testing for both allows for detection of drugs that may have been taken days or weeks before the urine test.

If a substance has been abused for a long period of time, it can sometimes affect how long it can be detected in a urine drug screen.


The chemical ethyl alcohol is present when a urine screen is positive for alcohol. This chemical is usually present for up to five days after an alcoholic beverage was last consumed.


Amphetamines can usually be detected for up to two days in the urine, and the test typically looks for methamphetamine (meth, ice), amphetamine (speed), MDMA/ecstasy (3,4-Methylenedioxymethamphetamine), MDA (3,4-Methylene dioxy amphetamine), and MDEA (3,4-methylenedioxy-N-ethylamphetamine).

There are select additional testing for other amphetamines, such as:

  • pseudoephedrine
  • phendimetrazine
  • diethylpropion
  • ephedrine
  • phentermine
  • phenylpropanolamine
  • Percocet


Barbiturates can be detected in the urine ranging from two days up to three weeks, depending if the barbiturate is long- or short-acting. The barbiturates usually included in a urine screen include amobarbital (Amytal), butabarbital (Fiorinal), pentobarbital (Nembutal), phenobarbital (Donnatal), secobarbital (Seconal).


Different types of benzodiazepines remain detectable in urine for different lengths of time. In addition, if a person takes benzodiazepines recreationally or for more than a year, it can extend the detection period for up to six weeks. If taken short-term, at a therapeutic dose, benzodiazepines typically are detectable for approximately three days. Examples of benzos include:


Cannabinoids and cannabis can be at detectable levels in a urine drug test for approximately two to seven days for a one-time use, but individuals who use marijuana for long periods of time can have a positive urine drug screen for up to two months. This is a result of the body storing chemicals from marijuana in fat cells.


Cocaine typically remains detectable in the system for around two to four days after the last use. Testing for a specific metabolite of cocaine, benzoylecgonine, is a good indicator of cocaine use. This chemical has no natural way of occurring in the body, so if it is in the system it means that the person ingested cocaine.


Opioids are either derived from the poppy plant or synthetic drugs that mimic the effects of natural opioids. Detection times vary as listed below:

PCP (1-phenylcyclohexyl piperidine hydrochloride) And LSD

PCP generally remains at detectable levels for 14 days, but when a person uses PCP long-term, the test can be positive for up to 30 days. PCP is also sensitive to variables in the body, like age, body mass, hydration levels, or health issues, which also leads to the varying time frame for positive results. LSD can stay detectable in your system for up to 12 hours after the last dose. However, 2-oxo-hydroxy-LSD, which is a metabolite of the drug, can be detected for up to five days.

What To Expect When Taking A Urine Drug Test

It will be expected that a valid form of identification is presented when taking a urine drug screen. Once inside the restroom, a sample must be provided in a specific amount of time. Do not flush the toilet. This will likely invalidate the test.

Once the sample is returned to the collector, they will likely conduct the test at that moment, otherwise, the sample will be labeled and sent to the lab for testing.

Make sure you take a copy of any prescription medications as well as supplements, vitamins, or over-the-counter medications you are currently taking.

If passing a urine drug test is a concern, or you believe that you or a loved one may be struggling with a substance use disorder, we are available to help. Contact a treatment specialist today for more information.

MDEdge: Journal of Family Practice - What common substances can cause false positives on urine screens for drugs of abuse?

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