Medical Tests

A B C D E F G H I J K L M N O P Q R S T U V W X All Medical Tests

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

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright ©2003 A.D.A.M., Inc., as modified by University of California San Francisco. Any duplication or distribution of the information contained herein is strictly prohibited.

Information developed by A.D.A.M., Inc. regarding tests and test results may not directly correspond with information provided by UCSF Medical Center. Please discuss with your doctor any questions or concerns you may have.