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Benzodiazepines Half-Life: How Long Do Benzos Stay In One’s System?

Last Updated: December 18, 2019

Authored by Sharon Levy, MD, MPH

Benzodiazepines are central nervous depressants that are prescribed to treat anxiety, seizures, panic attacks, and for inducing anesthesia. They are also used as muscle relaxants and to treat sleep issues and insomnia. The time for which benzos stay in one’s system depends on the half-life of benzodiazepines and several other factors. Read along further to find out about benzodiazepine half-life, their metabolism process, and how long do benzos stay in the system?

Benzos Half-Life

Benzodiazepines represent a class of drugs that are primarily used to treat anxiety induced by psychiatric or neurological disorders. They comprise several types of drugs with their mechanism of action and the types of disorders they treat. According to this study about the pharmacokinetic properties of benzodiazepines, the half-life of benzodiazepines is also different and depends on its different types. Benzodiazepines can be classified into three categories, each having its own average half-life duration.

Medical doctor discusses benzos half-life with female patient.

Short-Acting Benzos Half-Life

Short-acting benzodiazepines half-life is within 1 to 12 hours on average. These include Tranxene, Versed, Halcion, and others. Their duration of action is roughly between 3 to 8 hours, with a peak level achieved around 1-2 hours.

Intermediate-Acting Benzos Half-Life

They include medicines such as Xanax, Ativan, Prosom, and Restoril. Intermediate-acting benzodiazepines half-life is 12-40 hours on average with peak level achieved around 2 hours after administration.

Long-Acting Benzos Half-Life

The long-acting benzodiazepines have an average half-life of more than 40 hours, even up to 250 hours, in some cases. Long-acting benzos include Valium, Librium, Dalmane, and others.

Factors That Influence How Long Benzos Stay In The System

Several factors affect the process of benzodiazepines elimination from the body. Some of these are general factors, whereas others are individual factors that vary from person to person. These are described in detail below:

Half-Life Of The Particular Drug

Amount Of Benzos Taken

The dosage of the drug also affects the time it will take to eliminate it from the body. A higher dose will take more time for it to be excreted from the body as compared to a lower dose.

Various prescription benzos on white background.

Frequency Of Use

The frequency with which benzo is taken will affect the time it will take to eliminate it from the system. If taken for the long-term, it will take more time for the drug to stay in the system as compared to if it were taken for the short-term.

Interactions With Other Drugs

When benzos are taken in combination with other drugs or alcohol, it will take a longer time to eliminate from the system.

Age And Weight of Patient

Individual factors as the age, weight, and height of a person also affect the duration for how long benzos stay in a body system. These factors affect the rate of metabolism, which, in turn, affects the time any drug stays in the system.

Individual Metabolic Rate

The metabolic rate of each individual determines the time it will take the body to digest and eliminate drugs from the system.

Benzodiazepines Metabolism Process

The metabolism process of benzodiazepines effects how long benzos stay in the system. The process varies with the type of medications in question. The general metabolism process of a benzodiazepine starts when it is ingested. After that, it is broken down by the liver into different chemical components called metabolites. As described in the benzodiazepine metabolism chart in this study, some benzos such as lorazepam, temazepam, and oxazepam are metabolized in the liver through the process of glucuronidation. During the process of metabolism of benzos, there are no active metabolites. It also means that there are rarely any drug-to-drug interactions for such benzos.

Pill box and a glass of water.
The other principal pathway for benzodiazepine metabolism involves hepatic microsomal oxidation and breaking down to metabolites. Almost all metabolites of benzos created in this process are pharmacologically active with long half-lives. These metabolites can also be detected in BZD drug tests. The metabolites are mainly excreted by the kidneys.

Benzodiazepines Drug Test Detection

How Long Do Benzos Stay In The Urine?

How long benzos stay in urine depends on their half-life. After it is metabolized by the body, about 1/5th of the medicine stays in one’s urine for some time. The detection time may vary depending on the medicine or its metabolite in the urine sample. For slow-acting benzos, the detection time is approximately two days. For intermediate-acting benzos, the drug test will be able to detect the drug for up to 5 days. A benzodiazepine urine drug test will be able to detect long-acting benzos for up to 10 days after discontinuing the drug. A standard benzodiazepine urine test may not be able to detect every benzo or its metabolite. For such benzodiazepines, a urine drug test will be inconclusive, and other conclusive tests may be required for confirmation.

How Long Do Benzos Stay In The Blood?

The time for which benzodiazepines or their metabolites stay in the blood is relatively shorter than how long benzos stay in urine. Benzodiazepines can be detected in the blood within hours of its intake. However, the detection window in the blood is quite small. A blood test will only be able to detect benzos for 24 hours.

Man waiting for blood test for benzos.

How Long Does Benzodiazepine Stay in The Saliva?

A saliva test will be able to detect benzodiazepine in the saliva of an individual for up to 2 and a half days after its intake. This makes the detection window of saliva more than blood but less than urine. Saliva drug tests are relatively expensive and less common that blood, urine, or hair drug testing.

How Long Does Benzodiazepine Stay in The Hair?

A hair drug test will be able to detect benzos for up to 90 days after their intake. However, a hair drug test will not be able to detect benzodiazepine until after a few days of ingestion. The drug gets accumulated in the outgrowths of hair follicles, so a few days’ time is required for the drug to show up on the length of the hair. A hair drug test will be able to detect long-acting benzos with more accuracy than a short-acting benzodiazepine.

Do All Benzodiazepines Show Up The Same On A Drug Test?

No, all benzodiazepines show differently on drug tests. Short-acting benzos have a shorter half-life and are eliminated from the body much faster. These include benzos such as Xanax, Serax, Halcion, and Restoril. Hence, these benzos will only be able to be detected for a few hours after they are administered. Intermediate-acting benzodiazepines can be detected for longer durations in any kind of drug test as compared to shorter-acting benzos. They include Doral, Klonopin, and Mogadon. The long-acting benzodiazepines will be detected for longer duration as compared to the short and intermediate-acting ones. Drugs such as Valium, Librium, and Tranxene are included in this category.

Laboratory assistant filling medical report.
The properties of benzodiazepines of being water or fat-soluble also affect their drug detection time. Water-soluble benzo can be detected for longer durations than fat-soluble benzodiazepines. So, all benzos show up differently on a drug test.

What Can Cause A False Positive Drug Test For Benzodiazepines?

Certain factors can cause a false positive drug test for benzodiazepine. These include the use of Sertraline, a Selective Serotonin Reuptake Inhibitor (SSRI), and Oxaprozin, a non-steroidal anti-inflammatory drug (NSAID). According to this study about false-positive urine screening for benzodiazepines, it was concluded that a false positive benzodiazepine urine drug test was caused when Sertraline was used. The study results were cross-referenced to check if the individuals with a false positive benzodiazepine test were also prescribed Sertraline during that time. It was concluded that those individuals did, in fact, have an active Sertraline prescription.
If one is looking for getting clean from benzos, it is advised to seek professional detox help in certified medical centers.

Page Sources

  1. D. J. Greenblatt, R. I. Shader, M. Divoll, and J. S. Harmatz, “Benzodiazepines: A Summary of Pharmacokinetic Properties”,
  2. Connie Oshiro, “Benzodiazepine Pathway, Pharmacokinetics”,
  3. Kevin M. Nasky, DO, George L. Cowan, MD, MS, and Douglas R. Knittel, MD, “False-Positive Urine Screening For Benzodiazepines: An Association With Sertraline”, 2009,

Published on: December 5th, 2019

Updated on: December 18th, 2019

About Author

Sharon Levy, MD, MPH

After successful graduation from Boston University, MA, Sharon gained a Master’s degree in Public Health. Since then, Sharon devoted herself entirely to the medical niche. Sharon Levy is also a certified addiction recovery coach.


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