How Long Do Benzos Stay in Your System? A Practical Guide to Detection and Duration

Half-life vs. detection: what “stay in your system” really means

When asking how long benzodiazepines remain in the body, it helps to separate two ideas: the drug’s half-life and the detection window. Half-life describes how long it takes for the concentration of a medication to drop by half. Detection windows describe how long tests can find traces in different biological samples. These are related but not identical. A benzodiazepine can be undetectable by blood after a day or two yet remain identifiable in hair for months. The chemistry and metabolism of each specific drug play a major role, as do the type of test and personal factors like age, body composition, and liver function.

Common benzodiazepines vary widely. Shorter-acting options like alprazolam (often 6–20 hours) leave the bloodstream relatively quickly. Intermediate agents such as lorazepam (about 10–20 hours) or clonazepam (roughly 18–50 hours) decline more slowly. Long-acting agents such as diazepam have a half-life of 20–50 hours, and its active metabolites can persist far longer—desmethyldiazepam has reported half-lives that can stretch from 36 to well over 100 hours. Because of these metabolites, diazepam can be detectable for a substantially longer period than shorter-acting drugs, especially with chronic use.

Testing method matters. A blood test tends to capture recent use—often up to 6–48 hours for many benzodiazepines, and sometimes a bit longer for long-acting ones. Saliva tests generally detect use within 1–2 days, though performance varies by drug. Urine testing is most common: short-acting agents are often detectable for about 1–3 days after single or occasional use; longer-acting agents can be detectable for 7–10 days or more. In people who use high doses frequently, detection in urine can extend beyond two weeks and occasionally approach a month, especially for diazepam. Hair testing reflects a longer horizon—roughly 30–90 days—because drug compounds incorporate into the hair shaft over time.

Assays also differ in what they “look for.” Some standard urine immunoassays are better at detecting oxazepam-like metabolites and may miss lorazepam or clonazepam unless confirmatory methods (like GC-MS or LC-MS/MS) are used. That nuance explains why someone can take a benzodiazepine and still get a negative screening result, only to have a confirmatory test later show positive. For a detailed breakdown of test types and timeframes, see How long do benzos stay in your system.

Key factors that change how long benzos are detectable

Two people can take the same benzodiazepine and produce very different test results. Several variables make a measurable difference. The most obvious is the specific drug and dose. Short-acting benzodiazepines, taken at a low dose once, clear relatively quickly compared to long-acting agents taken at higher doses or on a repeating schedule. Chronic or heavy use allows drug and metabolites to accumulate in tissues, particularly in body fat, leading to longer detection windows in urine and hair.

Metabolism and liver function play an outsized role. Many benzodiazepines are metabolized by the cytochrome P450 enzyme system. For example, diazepam uses CYP2C19 and CYP3A4, while alprazolam relies heavily on CYP3A4. Genetic differences in these enzymes can speed up or slow down clearance. Medications that inhibit CYP3A4 (such as certain azole antifungals, macrolide antibiotics, or protease inhibitors) can prolong exposure, while enzyme inducers (like carbamazepine or rifampin) can shorten it. Liver disease generally slows metabolism, extending both clinical effects and detectability.

Age, body composition, and physiology matter, too. Older adults tend to have reduced hepatic clearance and more adipose tissue, which can store lipophilic benzodiazepines and their metabolites. A higher body fat percentage can act as a reservoir, modestly lengthening detection, especially for long-acting agents. Hydration status can dilute urine but doesn’t meaningfully change how fast the body eliminates the drug; it may, however, affect whether a borderline amount crosses a test’s positivity threshold.

Test sensitivity and specificity affect results. Standard immunoassays have detection limits; if the metabolite concentration falls below the cutoff, a result may read negative even if trace amounts remain. Some immunoassays are poor at recognizing certain glucuronidated metabolites—lorazepam is a classic example—so people taking lorazepam may have negative screens and positive confirmations. Confirmatory techniques like gas chromatography–mass spectrometry (GC-MS) or liquid chromatography–tandem mass spectrometry (LC-MS/MS) are much more precise and can detect lower levels for a longer period.

Finally, the distinction between clinical effects and detectability is important. Someone may no longer feel sedated or anxiolytic effects even while low-level metabolites remain detectable. Conversely, residual effects can persist after a single night’s sleep with some benzodiazepines, particularly in older adults, even if blood levels are falling. These nuances help explain why two timelines exist: the one for how long the drug affects a person and the one for how long a test can find it.

Real-world scenarios and timelines: from single dose to chronic use

Consider a few common scenarios that illustrate typical detection windows. A healthy adult takes a one-time, therapeutic dose of a short-acting benzodiazepine such as alprazolam. The drug’s effects generally wane within several hours, and a blood or saliva test might detect it for about a day, sometimes two. A urine screen often remains positive for roughly 1–3 days. A hair test performed a few weeks later could still show exposure, because hair archives drug incorporation over time.

Now compare that to an intermediate-acting option like lorazepam. Because it is extensively glucuronidated, routine immunoassays may miss it, but confirmatory tests will not. After a single dose, blood and saliva detectability commonly falls within 24–48 hours. Urine may show a positive for 2–4 days, occasionally longer if doses are higher or the person is older or has impaired clearance. With clonazepam, which has a longer half-life and unique metabolites, urine detection can stretch to about 5–9 days in some users, and confirmatory testing is often needed because standard screens may not catch its metabolites reliably.

For long-acting agents like diazepam, the picture shifts noticeably. Even a short course can linger in urine for 7–10 days. With regular, high-dose use over weeks or months, the combination of diazepam and its long-lived metabolites can be detectable for several weeks—sometimes approaching 3–4 weeks—especially in older adults or those with hepatic impairment. Blood tests still typically show shorter windows, often a few days at most, but urine and hair capture the longer story.

Case examples illustrate these ranges. A 35-year-old with a single 0.5 mg alprazolam dose prior to a flight might test positive on urine for about two days, turning negative by day three. In contrast, a 62-year-old taking diazepam daily for several months for muscle spasm may continue to produce positive urine screens two to three weeks after tapering off, due to slower metabolism and the persistence of active metabolites. A 45-year-old who took lorazepam intermittently may receive a negative point-of-care immunoassay yet a positive LC-MS/MS confirmation 48–72 hours later, reflecting assay limitations rather than true absence.

Patterns of use also matter. Intermittent, low-dose, short-acting use typically produces the narrowest windows of detectability. Frequent dosing or high cumulative exposure enlarges those windows, especially in urine and hair. Co-medications can push timelines in either direction: CYP inhibitors may prolong detectability, while inducers may shorten it. These dynamics underscore why charts listing neat numbers are starting points, not guarantees. A realistic framework is: blood 6–48 hours; saliva 1–2 days; urine 1–3 days for short-acting agents and 7–10 days or more for long-acting ones, with chronic use potentially extending beyond two weeks; hair roughly 30–90 days. When precise timing matters, understanding the specific benzodiazepine, the pattern of use, and the test method provides the most reliable estimate.