Health Encyclopedia

Benzodiazepines (Blood)

Does this test have other names?

Benzodiazepine drug screen

What is this test?

This is a blood test to screen for a class of drugs called benzodiazepines (ben-ZOH-die-AZ-uh-peens). Benzodiazepines are central nervous system depressants. They are used to sedate patients, help them sleep, prevent seizures, ease anxiety, and relax muscle spasms. These drugs are often informally called tranquilizers, sleeping pills, and muscle relaxants.

Variations in the molecules of different benzodiazepines give them their specific chemical properties and medical uses. 

Examples of common antianxiety medicines, muscle relaxants, and antiseizure medications include:

  • Alprazolam (Xanax)

  • Chlordiazepoxide (Librium)

  • Clonazepam (Klonopin)

  • Clorazepate (Tranxene)

  • Diazepam (Valium)

  • Lorazepam (Ativan)

  • Oxazepam (Serax)

Examples of common sedative-hypnotic medications include:

  • Temazepam (Restoril)

  • Triazolam (Halcion)

  • Flurazepam (Dalmane)

  • Estazolam (ProSom)

In addition to medical use, benzodiazepines are sometimes used illegally. Chronic abuse of benzodiazepines can lead to addiction, and combining these drugs with other depressants like alcohol can be fatal. Street names for these drugs include "downers," "benzos," "nerve pills," "candy," and "tranks." 

Why do I need this test?

Even if you have been prescribed these drugs, you may need this test if you are showing signs of an overdose. Symptoms of overdose include confusion, slurred speech, loss of muscular coordination, stupor, and unconsciousness. Benzodiazepines can also cause low blood pressure, slow or shallow breathing, and cardiac arrest.

You may also have this test if a health care provider suspects you are abusing the drugs illegally or without a prescription.

If you appear confused, cannot be roused, have seizures, or lose muscle control, you may also have this test as part of an overall drug screen to check for other commonly abused drugs. These screens vary at different hospitals, but often include tests for cocaine, opioids, amphetamines, barbiturates, benzodiazepines, marijuana or phencyclidine.

If you are conscious, able to talk with doctors, and willing to cooperate, you can provide information that helps health care providers determine the appropriate test for your situation. For example, if you are a victim of sexual assault, you may have this test to determine whether someone slipped a benzodiazepine date rape drug, such as Rohypnol ("roofie"), into your drink.

You might also be tested if doctors think you have taken benzodiazepines accidentally or in a suicide attempt. 

What other tests might I have along with this test?

If you seem to have an altered mental state, doctors will most likely give you a glucose test to check your blood sugar. If you are brought to a hospital showing symptoms of central nervous system depression, such as confusion, slurred speech, seizure, or coma, you may be tested for a variety of drugs, including benzodiazepines.

A benzodiazepine overdose alone is unlikely to cause coma or severe heart or lung function problems. If you have those symptoms, a doctor may screen for other drugs and test for causes of central nervous system depression that aren't drug-related.

In addition to a blood test, a doctor may also order a urine test for benzodiazepines, or a urine toxicology screen for a variety of substances. Urine tests are generally less expensive and less invasive than blood tests, but blood tests are harder for a patient to tamper with to hide drug abuse.

Exactly which lab tests you have depends on your physical exam and information about your condition that you are willing and able to provide. 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

The result of a benzodiazepine blood test is either positive or negative. A positive blood test for benzodiazepines may also be able to measure the amount of drug in the bloodstream.   

Different benzodiazepines have different therapeutic doses, ranging from 0.5 to 50 milligrams (mg). Overdoses of 10 of 20 times the prescribed dose of some benzodiazepines can result in a mild coma, but usually don't cause slow or shallow breathing. Most people recover.

But overdoses of fast-acting benzodiazepines like triazolam (Halcion) are more likely to cause breathing problems and even death.

A drug called flumazenil (Romazicon) may be used as an antidote to the sedative effects of benzodiazepines. It shouldn't be used in people who have been taking benzodiazepines over a long period to control seizures. In such cases, flumazenil could cause potentially fatal withdrawal. 

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Older adults and people with liver disease may not eliminate certain benzodiazepines as quickly as other people. Their test results may show higher levels from the same initial dose.

How do I get ready for this test?

You do not need to prepare for this test.