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Toxicology Screen

What Is a Toxicology Screen?

A toxicology screen is a test that determines the approximate amount and type of legal or illegal drugs that you’ve taken. It may be used to screen for drug abuse, to monitor a substance abuse problem, or to evaluate drug intoxication or overdose.

Toxicology screening can be done fairly quickly. The test is most often done using a urine or blood sample. In some cases, a sample of saliva or hair may be used. The results can show the presence of one specific drug or a variety of drugs at once. Further testing may be needed to determine the exact amount of a particular drug in the body and to confirm the results.

What Are the Different Types of Toxicology Screens?

There are four primary types of toxicology screening:

  • medical testing
  • employment drug testing
  • forensic analysis
  • athletics testing

Most screening methods use a sample of urine to test for the presence of drugs. In some cases, a blood, hair, or saliva sample may be used.

Why Is a Toxicology Screen Performed?

A toxicology screen may be done for various reasons. The test is often ordered to determine if someone has taken drugs that could endanger their health. Doctors will perform a toxicology screen if they suspect a person is taking illegal drugs and that person is showing the following symptoms:

  • confusion
  • deliriousness
  • unconsciousness
  • panic attacks
  • chest pain
  • difficulty breathing
  • vomiting
  • seizures

These symptoms usually indicate drug intoxication or overdose.

Employers who want to make sure their workers abstain from using illegal substances may also order a toxicology screen. In some cases, the test may be a normal part of the application process for certain jobs. It can also be used to check athletes for the use of performance-enhancing drugs, such as steroids.

People who work in law enforcement might perform a toxicology screen while investigating a car accident or sexual assault case. Officials can also order a test for people who are being monitored for illegal drug use, such as individuals on probation.

Other situations in which a toxicology screen may be performed include the following:

  • before receiving an organ transplant
  • during pregnancy, especially when there’s a history of substance abuse
  • during treatment for certain medical conditions, specifically those that require the use of pain medication

How Do I Prepare for a Toxicology Screen?

No special preparation is required for a toxicology screen. However, it’s important to tell the appropriate person about any prescription or over-the-counter medications you’re taking. Certain medications can interfere with the test results.

How Are Samples for Toxicology Screens Obtained?

A toxicology screen often requires a urine sample. The urine is collected in a small cup. In some cases, law enforcement or medical personnel are present to prevent tampering. You may be asked to remove outerwear such as a jacket, hat, or sweater and to empty your pockets as a precaution against tampering.

A blood sample may also used to screen for drugs. This type of test involves drawing blood into one or more small tubes. During a blood test, a healthcare professional inserts a needle into a vein and removes blood. Compared with a urine test, a blood test is more accurate in determining the concentration of a particular drug.

In some cases, a toxicology screen might be performed using a saliva or hair sample. The contents of the stomach can also be screened for drugs when doctors suspect someone has taken a drug orally.

All types of samples are sent to a laboratory for analysis.

What Types of Drugs Does a Toxicology Screen Detect?

Many substances can be discovered through toxicology screens. Common classes of drugs that may be detected by toxicology screens include:

  • alcohol, including ethanol and methanol
  • amphetamines, such as Adderall
  • barbiturates
  • benzodiazepines
  • methadone
  • cocaine
  • opiates, including codeine, oxycodone, and heroin
  • phencyclidine (PCP)
  • tetrahydrocannabinol (THC)

Depending on the drug, it may show up in the blood or urine within a few hours or weeks after being ingested. Certain substances, such as alcohol, are eliminated from the body fairly quickly. Other drugs, however, can be detected for several weeks after being used. One example is THC, which is in marijuana.

What Do the Results of a Toxicology Screen Mean?

Most toxicology screens provide limited information about how much or how often someone has taken a drug. The results of a toxicology screen are usually positive or negative. A positive test result means that a drug or multiple drugs are present in the body. Once your doctor identifies the presence of a drug by screening, a more specific test may be done that can show exactly how much of the drug is present. 

Content licensed from:

Written by: Dale Kiefer and Kristeen Cherney
Medically reviewed on: Jan 20, 2016: Deborah Weatherspoon, Ph.D, MSN, RN, CRNA

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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