Drug Tests

By Edmund Murphy

Last updated: 18 March 2024 & medically reviewed by Dr. Jenni Jacobsen

Understanding drug tests

A drug test is intended to identify any misuse of illegal substances or prescription drugs. Drug tests use samples of urine, saliva, sweat, blood, and hair to detect traces of specific drugs through immunoassay testing.^[1] 

These drug tests are most often used to detect the use of illegal substances such as cocaine or methamphetamines, but can also be used to detect the misuse of prescription drugs such as opioid painkillers or benzodiazepines as well as general substances of abuse such as alcohol.^[1]

Drug tests or screens can detect specific substances or can be used to identify a broad range of substances, depending on the type of test used.

• Common drugs screened for in tests include:^[1]

• Alcohol 

• Amphetamines (meth)

• Barbiturates (amobarbital)

• Benzodiazepines (Xanax, Valium, etc)

• Cocaine

• Marijuana (THC)

• Opioids (heroin, oxycodone, hydrocodone, codeine, fentanyl)

• Phencyclidine (PCP)

• Steroids

These are the drugs that are most commonly tested using what is called a 10-panel drug test. There are also other types of drug tests that screen for more substances, such as 14-panel tests, and others that look for smaller groups of drugs but with more concrete results, such as 5-panel tests.

Other names for drug tests

Drug screen, drug test, drugs of abuse testing, substance abuse testing, immunoassay testing, toxicology screen, tox screen, and sports doping tests are all terms that are used to describe drug tests.

Drug testing facts

All information shown is from analysis reported by Quest Diagnostics:^[2]

• Between January and December 2021, the overall rate of positive drug tests rose from 4.4% to 4.6% in the US general workforce.

• The rate of opioid detection dropped slightly from 0.33 to 0.32%.

• Marijuana results rose to 3.9% of positive samples (3.6% in 2020), though overall testing for marijuana has declined due to the greater legalization of marijuana.

• Positive results from post-accident tests increased 26% from 7.7% to 9.7%.

• Positivity for cocaine based on urine tests in the general U.S. workforce decreased 4.5% (0.22% in 2020 versus 0.21% in 2021) and positivity for cocaine over the past five years declined 30% (0.30% in 2017 versus 0.21% in 2021).

What types of drug test are there?

While urine testing is the most common form of drug test owing to its ease of use, relative accuracy, and ready availability, there are several other types of drug test used for specific drug screening or further accuracy. These include:

• Urine testing

• Blood testing

• Saliva testing

• Hair follicle testing

• Sweat testing

• Residue testing

• Breath testing

What are panel drug tests?

What drugs do not show up in drug tests?

While 5, 10, and 15-panel tests are designed to detect the most common and easily identifiable drugs, there are many substances that are difficult to detect or can’t be detected at all. These include;

• Psychedelics/hallucinogens - substances such as LSD, psilocybin, DMT, and mescaline are extremely difficult if not impossible to detect in drug screenings as they are metabolized extremely quickly. Hair follicle tests may be used to detect psychedelics, but this is rare as they are expensive and time-consuming.

• GHB - Gamma hydroxybutyrate, better known as GHB or the date rape drug, is almost completely undetectable in the system within 12 hours of consumption. This makes it hard to determine if it was used in cases of date rape, making convictions difficult. 

• Designer drugs - Research chemicals or designer drugs are compounds found in various synthetic substances (such as bath salts or “spice”) that are very hard to detect with standard drug tests. These substances are often highly modified to give unique highs or to mimic the effects of other substances such as meth or cocaine. 

Why would you be asked to take a drug test?

Drug testing is used in many areas to identify drug misuse, such as by employers, in sporting fields, and in legal cases. Despite popular misconceptions, drug tests are not used to identify a substance use disorder, addiction, or dependence. How and where drug tests can be performed varies with individual state law, with some states offering more freedom for randomized drug testing than others.^[4]

Common areas drug tests are used for include:

• Employment - It is becoming increasingly prevalent for employers to screen candidates for substance abuse with drug tests before employing. Some employers also perform regular drug tests throughout employment as well as testing after a work-related accident to ensure drugs or alcohol were not involved.

• Sports - Professional athletes are often screened for performance-enhancing drugs such as steroids or any other substance that may give them an edge in competition. 

• Law enforcement - There are several instances that a drug test may be used in legal settings. This includes breathalyzing suspected DUI drivers, as part of evidence in a court case, random prison screenings, and others.

• Entering drug treatment - Addiction treatment centers will often screen new patients to identify what if any substances they currently have in their system. This is especially important for those undergoing medically assisted detox so the correct course of medication can be administered safely. 

• Monitoring prescription drug use - A doctor may order a drug test if you are on a course of medication that is potentially addiction-forming or if you have a history of drug abuse. 

• Educational settings - Some schools and higher education settings have the right to administer drug tests if they have reasonable doubt about a student's potential drug use. Drug testing in educational settings is often more common in student-athletes, especially those on a sports scholarship.

• The military - New recruits and soldiers may be randomly tested for drugs to make sure they are combat effective. 

In all of the above cases, drug tests may be scheduled in advance or ordered randomly without advanced warning. Read here to learn more about how drug tests work.

Preparing for a drug test

Most drug tests are performed at random so that those being tested don’t have time to influence the results. To ensure that results are read as accurately as possible, it is important to be 100% honest and clear with whoever is administering the test about any substances or over-the-counter medication you have taken so that test results are read clearly. 

You should also avoid certain foods and herbal remedies that may generate a false positive on a test. Food and drug products that may interfere with drug tests include poppy seeds (for opioid tests), hemp products (marijuana), sleep aids (barbituates), hay fever remedies (amphetamines), and diet pills (amphetamines).^[5]

Be sure to know the reason you are being tested and what you are being tested for before you start. Seek any additional information from the test provider or organization asking for the test if you are unsure or uncomfortable.

Understanding drug test results

A negative result for any drug test indicates that none of the drugs screened for were identified or that their presence was below the cutoff point in the person's system.^[4]

A positive result means that a substance or substances were detected in the system. A positive result will often require a follow-up test to either determine more accurately what drugs were detected or to rule out a false positive result. 

If a positive result comes in for a drug you are prescribed by your doctor, such as benzodiazepines, your employer cannot legally penalize you. This does not apply to marijuana, even if it is legal in your state, and your employer has the right to penalize you if it falls within their drug policy to do so. 

Drug test FAQs

Here are some common questions asked about drug tests.

Do drug tests screen for alcohol?

Yes, all drug tests have the ability to screen for alcohol in a person's system, though being asked to perform a drug test for alcohol is uncommon outside of breathalyzer tests. While it is easily possible to detect alcohol such as ethanol in drug tests, it is uncommon for employers and other organizations to test for it as it is a legal substance. Your employer may ask you to test for alcohol if you have been suspended for alcohol-related reasons.

Which drug panel test is best for employers to use?

There are no right or wrong drug tests to use as it depends on a variety of factors. For employers, the right drug test to use will depend on your industry, legal requirements, geographic location, and risk factors for employees, with a 5-panel drug test being fine for some while others may need a 21 or higher panel test. For at-home drug tests, a 10-panel drug test will be able to screen for a variety of commonly abused substances.

How long will drugs show up in a drug test?

The amount of time drugs are detectable in your system and from what point they become detectable in drug tests varies drastically from substance to substance. It can also vary from person to person and is influenced by factors such as age, weight, and gender. Read here to learn more about how long substances stay in your system.

Can you fake a drug test?

No, you cannot fully fake a drug test. While the internet is full of supposed tricks for fooling a drug test (often for at-home tests), the simple answer is that these methods will often make a drug test inconclusive, which will result in a further, often more rigorous, drug test.

Are there risks associated with drug tests?

There are no known physical or psychological risks associated with drug tests. However, the results of the test may have serious ramifications for employment, sporting eligibility, and the outcome of any legal matters pertaining to the test.

Do edibles show up in drug tests?

Yes, the metabolites contained in most substances used in edibles can be detected in drug tests. While the THC in edibles is detectable in drug tests, as is psilocybin in mushroom edibles, the metabolites will be in smaller quantities and may pass standard drug tests that have a higher cut-off point for these substances.