Drugs of abuse testing is used to screen for and confirm the presence of several drugs in a person's sample, such as urine, blood or hair. Drug testing is used so that a person may receive appropriate medical treatment or be screened for or monitored for illegal drug use.

Some of the most commonly screened drugs include:

• Amphetamine and methamphetamine
• Barbiturates such as phenobarbital, secobarbital and pentobarbital
• Benzodiazepines such as diazepam, lorazepam and oxazepam
• Marijuana
• Cocaine
• Methadone
• Opiates, such as heroin, codeine and morphine
• Phencyclidine (PCP)

(See a more comprehensive list of drug classes and drugs of abuse.)

Drugs of abuse testing may be used for:

• Medical screening
• Legal or forensic information
• Employment drug testing
• Sports/athletics testing
• Monitoring pain medication use

Medical Screening 
Medical screening for drugs of abuse is primarily focused on determining what drugs or combinations of drugs a person may have taken so that the person can receive proper treatment. A drug's overall effect on a particular person depends on the response of the person's body to the substance, on the quantity and combination taken, and when it was taken. For instance, MDMA (also known as Ectasy or Molly) is initially a stimulant with associated psychedelic effects but later causes central nervous system (CNS) depression as it is metabolized and cleared from the body. In many cases, drugs have been combined and/or taken with ethanol (alcohol). If someone drinks ethanol during this time period, the person will have two CNS depressants in their system, a potentially dangerous combination.

A health practitioner may order drug testing for medical reasons if an individual:

• Has acute health problems that may be drug-related or shows signs of intoxication, such as unconsciousness, nausea, delirium, panic, paranoia, increased temperature, chest pain, respiratory failure, seizures, and/or headaches
• Has injuries from an accident that an emergency room physician suspects are due to drugs and/or alcohol
• Is suspected of drug use or is known to use legal and/or illegal drugs
• Is a candidate to receive an organ transplant
• Is pregnant, especially if she is thought to be at risk for drug abuse or has a newborn baby exhibiting certain characteristic behaviors
• Is on pain medication, to ensure that the person is taking the medication as prescribed

For a more in-depth discussion of this, see the article Emergency and Overdose Drug Testing.

Legal or Forensic Testing 
Drug testing for legal purposes primarily aims to detect illegal or banned drug use in a variety of situations. Sample collection procedures for this type of testing are strictly controlled and documented to maintain a legal "chain-of-custody." The donor provides a sample that is closed and secured with a tamperproof seal in his or her presence. Specific chain-of-custody paperwork then accompanies the sample throughout the testing process. Each person who handles and/or tests the sample provides their signature and the reason for the sample transfer. This creates a permanent record of each step of the process.

Examples of legal drug abuse screening include:

• Court-mandated testing usually involving random monitoring of someone who has been convicted of illegal drug use or to rule out drug use by parents involved in custody cases.
• Extended monitoring of a parent with a history of drug abuse, ordered by government child protective services to ensure that the person has not resumed use of substances.
• Testing by law enforcement when alcohol and/or drugs are thought to be involved in an accident
• Forensic toxicology testing using a variety of body fluids and tissues that may be tested during a crime investigation; the goal may be to determine whether drugs were a contributing factor to an accident or crime, such as DUI (driving under the influence) or rape. Testing may also determine whether someone died of a drug overdose or drug-related condition.
• Applicants for life insurance may undergo drug screening, possibly including tests for cocaine and nicotine, even though tobacco is a legal substance.
• Schools may have programs that incorporate random drug testing. Such programs may look for use of illegal drugs or performance-enhancing substances among athletes.

For additional information on this type of testing, see the article on The World of Forensic Laboratory Testing.

Employment Drug Testing 
Employment drug testing is a specific type of forensic testing (see above). It may be done prior to employment, on a random basis, following an accident, or if the employer has a reasonable suspicion that an employee is using illegal drugs. Employment drug testing is commonplace. It is required in some industries, such as those that involve the U.S. Department of Transportation, the military and federal employees, and is an accepted practice in many other industries.

As with legal or forensic drug testing, the sample collection and testing procedures for employment drug testing are often strictly controlled and documented to maintain a legal "chain-of-custody."

Sports/Athletics Screening 
While conventional drug testing is performed on competitive athletes, the primary focus is on doping, the use of drugs and/or supplements intended to promote muscle growth and/or to improve strength and endurance. On a local level, sports testing may be limited, but on a national and international level, it has become highly organized.

The World Anti-Doping Agency (WADA), U.S. Anti-Doping Agency (USADA), and the International Association of Athletics Federations (IAAF) work together to monitor athletes' drug use on a national, international, and Olympic level. WADA has a written code that establishes uniform drug testing rules and sanctions for all sports and countries and that includes a substantial list of prohibited substances. Athletes are responsible for any banned substances found in their body during testing.

Most compounds are prohibited in any quantity, while others, such as caffeine, are only prohibited when they are present in large amounts. Some of the substances, such as anabolic steroids (testosterone) and peptide hormones such as erythropoietin, growth hormone, and insulin-like growth factor-1 are banned but are difficult to measure because the body also produces them naturally. Testing methods must be able to distinguish between endogenous (that produced by the athlete's body) and supplemented compounds.

Screening programs randomly perform out-of-competition drug tests on athletes during the training season to look for anabolic steroids, such as testosterone, that promote increased muscle growth. During competitions, testing is frequently done both randomly and on all winners.

Testing includes categories such as stimulants, narcotics, anabolic agents, and peptide hormones. WADA bans use of beta blockers in archery, golf, shooting, freestyle skiing, and snowboarding because they decrease blood pressure and heart rate and have a calming effect that can enhance balance and steadiness of the hands.

While professional sports organizations, such as the NFL (National Football League), NHL (National Hockey League), and NBA (National Basketball Association), are not covered by the WADA code, they have programs in place to test their athletes for panels of drugs that combine aspects of sports and employment testing. Those professional athletes who also take part in the Olympics, however, are subject to Olympic regulations.

Monitoring Pain Medication Use
Drug screening in urine is the method of choice for monitoring adherence to prescription pain medications in patients treated for chronic pain. Urine drug screening provides tools for tracking patient compliance and exposing possible drug misuse and abuse. A health practitioner may periodically order drug testing for patients treated for chronic pain for two purposes: 1) ensuring compliance by patients who are using the prescribed pain medications, and 2) monitoring the use of non-prescribed or illegal substances. Elements of a urine drug screen may include specific gravity, temperature at the time of sample collection, pH, creatinine concentration, and confirmatory testing.

Compliance monitoring of pain medications is crucial for eliminating or significantly curtailing abuse (e.g., addiction, diversion) of controlled prescription drugs and at the same time assuring the appropriate treatment for those patients who can be helped by these medications. Urine drug screening is considered one of the mainstays of adherence monitoring in conjunction with prescription monitoring programs and other screening tools.

Drug testing is performed whenever a health practitioner, employer, legal entity, or athletic organization needs to determine whether a person has illegal or banned substances in his or her body or is compliant with prescribed medications. It may be ordered prior to the start of some new jobs and insurance policies and at random to satisfy workplace, court-ordered, adherence monitoring, or athletic drug testing program requirements.

Drugs of abuse testing may also be ordered by a health practitioner to monitor a known or suspected substance abuse patient or whenever a person has signs and symptoms that suggest drug use. Depending on the drug or drugs involved, these may include, for example:

• Dilated or small pupils
• Drowsiness
• Slow or slurred speech
• Agitation
• Nausea
• Difficulty breathing
• Delirium
• Seizures
• Changes in blood pressure or heart rhythm

A positive initial drug screening means that the person tested has a substance in his or her body that falls into one of the drug classes and is above the established cutoff level. If secondary testing confirms a positive result, it means that the person has indeed taken this drug.

In some cases, this result indicates a window of time in which the person took the substance and its approximate quantity, but in most circumstances, that information is not necessary. Interpretation of when and how much drug was consumed can be challenging because the concentration of many drugs varies, as do people's rates of metabolism.

If testing reveals no drugs, or drugs in amounts below the established cutoffs, then the results are usually reported as "not detected" or "none detected."

A negative result does not necessarily mean that the person did not take a drug at some point. The drug may be present but below the established cutoff, the drug may have been already metabolized and eliminated from the body, or the test method does not detect the particular drug present in the sample.

Tests of different body samples reveal drug use within varying windows of time. For example:

• Urine testing shows drug use over the last 2 or 3 days for amphetamines, cocaine, and opiates. Marijuana and its metabolites, cannabinoids, may be detectable for several weeks. Methadone, barbiturates and benzodiazepines can be detected for about a week.
• Hair samples, which test the root end of the hair, reflect drug use within the last 2 to 3 months but not in the amount of time it takes for the hair to grow, the most recent 2 to 3 weeks.
• Saliva detects which drugs have been used in the last 24 hours.
• Samples of sweat may be collected on an absorbent patch worn for several days to weeks and therefore can indicate drug use at any point during that extended period of time.

Different types of samples are often used for specific purposes. For instance, hair samples may be used as an alternative to urine testing for employment or accident drug testing. Sweat testing may be used as a court-ordered monitoring tool in those who have been convicted of drug use, while saliva is often used by the insurance industry to test insurance applicants for drug use. Blood is most frequently used for alcohol testing.

Interpretation of sports testing results for hormones and steroids should be done only by laboratory professionals who are familiar with particular test methods. A negative result indicates that there is a "normal" amount of the substance present in the body. Positive results reflect the presence of the substance above and beyond what is normally produced by the athlete's body. These results can be complicated by the fact that each person will have his or her own normal baseline concentration and will produce varying amounts of hormones and steroids, depending upon the circumstances.

Symptoms associated with drug abuse and drug overdose will vary from person to person, from time to time, and do not necessarily reflect drug concentrations in the body.

Ethanol may be measured in both the blood and the breath. This is the basis for the breathalyzer test used by law enforcement.

For some types of testing, such as workplace testing of federal employees, there are many regulations that cover the test from collection through interpretation and reporting of results. It is important for the ordering physician, law enforcement representative, forensic professional, government entity, insurance agent, employer, and sports organization as well as for the person being tested to understand what exactly is included in the testing, how it is done, and how the results may or may not be interpreted. This process is not nearly as simple or straightforward as collecting a sample and requesting "drug testing."

Prescription drug monitoring programs incorporate urine drug testing as part of the process of monitoring adherence to prescription pain medications.