Health Encyclopedia

Toxicology screen

Definition

A toxicology screen refers to various tests to determine the type and approximate amount of legal and illegal drugs a person has taken.

Alternative Names

Barbiturates - screen; Benzodiazepines - screen; Amphetamines - screen; Analgesics - screen; Antidepressants - screen; Narcotics - screen; Phenothiazines - screen; Drug abuse screen; Blood alcohol test

How the test is performed

Toxicology screening is most often done using a blood or urine sample. However, it may be done soon after swallowing the medication, using stomach contents that are obtained through gastric lavage or after vomiting.

For information on giving a blood sample from a vein, see venipuncture.

For information providing a urine sample, see clean catch urine sample. In some circumstances, you may need to provide the urine sample in the presence of the nurse or technician to verify that the urine sample came from you and was not tampered with.

How to prepare for the test

No special preparation is needed. If able, tell your health care provider what drugs (including over-the-counter medications) you have taken, including when and how much.

This test is sometimes part of an investigation for drug use or abuse. Special consents, handling and labeling of specimens, or other special procedures may be required.

How the test will feel

Blood test:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Urine test:

A urine test involves normal urination. There is no discomfort.

Why the test is performed

This test is often done in emergency medical situations. It can be used to evaluate possible accidental or intentional overdose or poisoning. It may help determine the cause of acute drug toxicity, to monitor drug dependency, and to determine the presence of substances in the body for medical or legal purposes.

Additional reasons the test may be performed:

Alcoholism
Alcohol withdrawal state
Altered mental state
Analgesic nephropathy
Complicated alcohol abstinence (delirium tremens)
Delirium
Dementia
Drug abuse monitoring
Fetal alcohol syndrome
Intentional overdose
Stroke secondary to cocaine
Unconscious patient

If the test is used as a drug screen, it must be done during a certain time period after the drug is taken or while forms of the drug can still be detected in the body. Examples are below:

Alcohol: 3 to 10 hours
Amphetamines: 24 to 48 hours
Barbiturates: up to 6 weeks
Benzodiazepines: up to 6 weeks with high level use
Cocaine: 2 to 4 days; up to 10 to 22 days with heavy use
Codeine: 1 to 2 days
Heroin: 1 to 2 days
Hydromorphone: 1 to 2 days
Methadone: 2 to 3 days
Morphine: 1 to 2 days
Phencyclidine (PCP): 1 to 8 days
Propoxyphene: 6 to 48 hours
Tetrahydrocannabinol (THC): 6 to 11 weeks with heavy use

Normal Values

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

A normal value usually means that alcohol, prescription medications that are not prescribed, and illegal drugs are not found.

A blood toxicology screen can determine the presence and level (amount) of a drug in your body.

Urine sample results are usually reported as positive (substance is found) or negative (no substance is found).

What abnormal results mean

Elevated levels of alcohol or prescription drugs can be a sign of intentional or accidental intoxication or overdose.

The presence of illegal drugs or drugs not prescribed for the person indicates illicit drug use.

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)

Special considerations

Commonly found substances on a toxicology screen include:

Alcohol (ethanol) -- "drinking" alcohol
Amphetamines
Antidepressants
Barbiturates and hypnotics
Benzodiazepines
Cocaine
Marijuana
Narcotics
Non-narcotic pain medicines including acetaminophen and anti-inflammatory drugs
PCP
Phenothiazines (antipsychotic or tranquilizing medications)
Prescription medications, any type

Review Date:10/29/2007
Reviewed By:Eric Perez, MD, Department of Emergency Medicine, St. Luke's-Roosevelt Hospital Center, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

ADAM Quality A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

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