Urine screens are the most common method of drug testing. They are painless, easy, quick, and cost-effective. They can also check for both illegal and prescription drugs.
The person provides a urine sample, and a doctor or technician analyzes it.
The analysis can determine whether a person has used specific drugs in the past few days or weeks, even after the effects of the drugs have worn off.
In this article, we take a close look at urine drug screens. We describe the types of drugs they can detect and how long these substances remain traceable in urine.
We also discuss the steps of the test, the results, and how to prepare.
Purposes and uses of urine drug screens
Doctors, sports officials, and employers may request urine drug screens for a range of reasons.
Drug screening can test for both illegal and prescription drugs.
A doctor may request a urine drug screen if they think that a person has been using illegal drugs or misusing prescription drugs.
For example, a doctor may request a urine screen to determine if a person is misusing the opioids that the doctor had prescribed to treat their chronic pain.
An emergency services staff member may request a urine drug screen if they suspect that a person is behaving strangely or dangerously due to the influence of drugs.
Drug and alcohol rehabilitation programs may request urine drug screens to check whether a person is staying sober.
Prison officials also require these tests of people with histories of drug abuse.
Many sporting officials require urine drug screens to check whether athletes have used performance-enhancing drugs.
Some employers request that new or existing staff members take urine drug screens.
This is more common in workplaces that require high levels of safety. An employer may be more likely to test a person who operates vehicles or machinery, for example.
Employee drug testing laws differ, and a person should check with local authorities.
Which drugs can a urine test detect?
A urine drug screen can detect a range of drugs. These include:
- phencyclidine (PCP)
A urine test can indicate the level of alcohol in a person's body. However, if a person suspects alcohol consumption, they are more likely to request a breath or blood test.
Urine screens can also detect nicotine and cotinine, which the body produces when it breaks down nicotine.
Procedure and types of urine test
A doctor or trained technician will usually carry out the urine drug screen.
There are two types of urine drug screens, and both require a sample.
An immunoassay (IA) test is the most common type, because it is the quickest and most cost-effective.
However, it can give a false-positive result. This shows the presence of a drug when a person has not used it.
A second type of urine screen can confirm the results of an IA test. The second test is called gas chromatography-mass spectrometry (GC-MS).
GC-MS is a more reliable method of screening than IA. It can also detect a wider range of drugs.
Usually, providers only use GC-MS tests as follow-ups because they are more expensive, and the results take longer to receive.
How reliable are urine drug screens?
Eating poppy seeds prior to the test may give a false-positive result.
Urine drug screens use cut-off levels. This means that a result will only be positive if the amount of the drug is above a certain level.
The amount of the drug will appear on results in nanograms per milliliter: ng/ml.
Having cut-off levels helps prevent false-positive results. These can occur when a person has not taken an illegal drug, but they have eaten food containing a legal amount of hemp, coca, or opium.
For example, eating poppy seeds before a urine drug screen can, in rare cases, cause the test to detect the presence of opium. The United States Anti-Doping Agency advise against eating poppy seeds before taking a drug test.
Cut-off levels also reduce the chance of a person testing positive after only passive exposure to a drug. Secondhand smoke is one example of passive exposure.
Also, both IA and GC-MS tests can produce false-negative results. These fail to indicate that a person has recently done drugs. A false-negative result can occur if the urine is very diluted.
Many factors affect the length of time that a test can detect a certain drug in the body. These factors include:
- body mass
- hydration levels
- the acidity of the urine
- how long ago the person took the drug
If a person uses a drug very frequently or heavily, a urine test will detect the drug for a longer period.
For example, the detection times for marijuana can depend on how often a person uses it:
|Frequency of marijuana use||Detection times after use|
|Single use||3 days|
|Moderate use, or 4 times per week||5–7 days|
|Daily use||10–15 days|
|Heavy use||more than 30 days|
This table shows how long a urine test can detect certain drugs after a person has taken them:
|Drug||Detection time after use|
|Short-acting barbiturates||24 hours|
|Cocaine metabolites||2–4 days|
|Short-acting benzodiazepines||3 days|
|Long-acting barbiturates||3 weeks|
|Long-acting benzodiazepines||30 days|
How to prepare for a urine test
It is essential to make the test provider aware of any prescribed medication.
The test requires little preparation. Usually, a person just has to urinate into a plastic container.
It is important to note that certain medicines and supplements can cause false-positive results that indicate illegal drug use.
A person should tell the test provider if they are taking any:
- prescription medications
- over-the-counter medicines
- herbal remedies
A medical professional or technician will carry out the urine drug screen. They may start by asking a person to:
- empty their pockets
- remove any excess clothing and items, such as bags and coats
- clean their hands with antibacterial gel or soap and water
- clean their genital area with a wipe, which the technician will provide
The technician will then instruct a person to:
- urinate into a container, until the level of urine reaches a certain point
- put the lid on the container and return it to the technician
The technician will then measure the temperature of the urine sample to ensure that it is suitable for testing. They will then seal the sample in a plastic bag.
Both the donor and the technician should keep an eye on the sample until it is sealed, to make sure that no one has tampered with it.
Sometimes, the technician will accompany the person into the test room to make sure that they are giving the sample correctly. The technician should explain the reason for this supervision.
Interpreting the results
Urine drug screen results usually come back within a few days. Some results come back on the same day.
Negative results may come back more quickly. A positive result may take longer, because ensuring the accuracy may require further testing.
If a result is positive, a person will need to take a second test for confirmation. This will be a GC-MS test, which will provide more accurate results.
The person who carried out the test or a medical review officer will explain the results.
A urine drug screen can quickly and effectively detect the presence of illegal or prescription drugs in the body.
Doctors, sports officials, and employers may request a urine drug screen for various reasons.
These screens can check for a range of drugs, including marijuana, nicotine, barbiturates, and opioids, such as heroin and methadone. Some drugs remain traceable in the body longer than others.
If an initial result is positive, a person may need to take a second test for confirmation.