The short answer
There is no single benzodiazepine window. In urine, a single dose of alprazolam (Xanax), lorazepam or oxazepam is detectable for 24 to 72 hours — while daily diazepam (Valium) runs 14 to 42 days and daily clonazepam 14 to 21 days. Blood is short for all of them: 6 to 24 hours for the short-acting molecules, 24 to 96 hours for diazepam.
That spread is not sloppy reporting. Five of the seven molecules modelled here are cleared within a day or two of the dose. The other two — diazepam and clonazepam — are long-acting, they build up when taken every day, and diazepam carries an active breakdown product that outlives the drug itself. Quoting one number for "benzodiazepines" without naming the molecule is meaningless.
How long is each benzodiazepine detectable in blood, saliva and urine?
| Molecule | Half-life | Blood | Saliva | Urine |
|---|---|---|---|---|
| Diazepam (Valium) | 46 h | 24–96 h | 6–120 h → 48–168 h | 3–7 d → 14–42 d |
| Clonazepam (Rivotril, Klonopin) | 35 h | 24–48 h | 6–60 h → 24–144 h | 3–7 d → 14–21 d |
| Bromazepam (Lexotan) | 17 h | 6–24 h | 4–24 h | 2–4 d → 4–7 d |
| Lorazepam (Tavor, Temesta, Ativan) | 14 h | 6–24 h | 2–18 h | 1–3 d → 4–7 d |
| Alprazolam (Xanax) | 11.2 h | 6–24 h | 2–18 h | 1–3 d → 3–7 d |
| Oxazepam (Praxiten, Seresta) | 7 h | 6–24 h | 4–24 h | 1–3 d → 4–7 d |
| Etizolam (Etilaam, Etizest) | 3.4 h | 6–24 h | 4–24 h | 2–3 d → 4–7 d |
Saliva only lengthens with daily use for diazepam and clonazepam; for the other five the daily window is the same as the single-dose one, because they are gone before the next dose. Reference cutoffs are per molecule: blood 5–50 ng/mL (alprazolam, clonazepam and etizolam 5; lorazepam 10; bromazepam 20; diazepam and oxazepam 50) and saliva 2–10 ng/mL. Clearhead carries no numeric urine cutoff for this class — those windows are fixed constants tied to standard screening practice, so we publish them without a threshold rather than invent one. Estimates, not measurements.
Blood is the only benzodiazepine matrix Clearhead scales with dose: the figures above are a floor the app can extend for a larger dose or a slower profile, never shorten.
Why a negative benzodiazepine urine test does not mean it has cleared
A urine screen for this class is a single immunoassay pointed at a family of chemically quite different molecules. It handles some well and misses others — and the ones it misses are among the most widely used.
| Screen behaviour | Molecules |
|---|---|
| Reflected reliably | Diazepam, oxazepam |
| Variable | Bromazepam |
| Often missed — unreliable | Alprazolam, clonazepam, lorazepam |
| Not detected at all | Etizolam |
Read that in the right direction. A negative class screen after alprazolam, clonazepam or lorazepam is weak evidence: the test frequently fails to flag them even when they are present. After etizolam it is no evidence at all — a thienodiazepine sold on the designer market, it needs a targeted laboratory method to be seen. A negative result should never be read as "it has gone".
The trap runs the other way too. Diazepam is one of the two the screen does reflect reliably, but a sensitive laboratory confirmation reads its metabolite tail far longer than the screen window — so a negative screen on day 5 does not tell you a lab test would agree.
Why diazepam stays detectable for weeks and alprazolam for days
Diazepam has a half-life of 46 hours, and it converts to nordiazepam, an active metabolite with a half-life of about 90 hours. That metabolite, not the parent drug, is the long tail. On daily dosing it builds up nearly sixfold, which is how a urine window that is 3 to 7 days after one tablet becomes 14 to 42 days in a daily user.
Accumulation here is close to binary rather than a matter of degree: between two daily doses, a benzodiazepine either clears or it does not. Only diazepam and clonazepam (half-life 35 hours) are long-acting enough to build up. Bromazepam at 17 hours, lorazepam at 14, alprazolam at 11.2, oxazepam at 7 and etizolam at 3.4 are effectively gone before the next dose arrives — which is why their daily-use windows barely move.
The same metabolite explains a figure you will see quoted wrongly. Diazepam's saliva window is often given as 48 hours. Clearhead deliberately estimates about five days for a single dose, because the oral-fluid assay also reads nordiazepam — measured at a median of 132 hours at a 1 ng/mL limit of quantification (Vindenes 2019). A 48-hour figure would falsely reassure.
What moves the window: age, body fat and daily use
Age — but only for some of them
Age slows the CYP-metabolised benzodiazepines markedly and the glucuronidated ones barely at all. From middle age onwards diazepam and clonazepam lengthen substantially (Klotz 1975); alprazolam, bromazepam and etizolam lengthen less; lorazepam and oxazepam — cleared by glucuronidation, a simpler route that ageing hardly slows — are almost unaffected.
Body fat — heaviest on diazepam
The lipophilic molecules stretch with body fat. It weighs most on etizolam and diazepam, and matters most in practice for diazepam, whose long metabolite tail it extends further still: Abernethy 1982 measured desmethyldiazepam at 154 hours in obese subjects against 57 hours in lean ones. The glucuronidated pair, lorazepam and oxazepam, barely moves.
What Clearhead does not model
Kidney and liver function are not modelled for benzodiazepines at all, unlike for opioids. Where the app has no lever, we say so rather than publish a number that would look precise and mean nothing.
If you take benzodiazepines on prescription
Most people asking this question are patients, not recreational users. A prescription changes the legal and workplace frame around a positive result — it does not change the pharmacology. The same molecule at the same dose produces the same window either way.
One thing worth saying plainly: if you take a benzodiazepine daily and you are thinking about stopping, do not stop abruptly — withdrawal from this class can be genuinely dangerous, and a doctor can plan a gradual taper with you.
Driving: a detection window is not a statement about impairment
None of the numbers on this page tell you whether you may drive. They describe when a sample is expected to fall below a reference cutoff, which is a laboratory question, not a legal or a functional one. Long-acting benzodiazepines can still affect alertness and reaction time the morning after a dose, even when you feel fine — while a urine screen can stay positive for weeks after any effect has ended. Neither result is permission. For a sense of how differently jurisdictions handle numeric blood thresholds where they exist at all, our THC limits by country page sets out the per-country picture for cannabis.
Frequently asked questions
How long do benzodiazepines stay in your system?
It depends entirely on which one. In urine, a single dose of alprazolam, lorazepam or oxazepam is detectable for 24 to 72 hours, while daily diazepam runs 14 to 42 days. Blood is short for all of them: 6 to 24 hours for the short-acting molecules.
How long is Xanax (alprazolam) detectable?
Alprazolam has a half-life of 11.2 hours and does not accumulate. Blood 6 to 24 hours, saliva 2 to 18 hours, urine 24 to 72 hours after a single dose and 3 to 7 days on daily use. A standard class screen often misses it.
How long is diazepam (Valium) detectable?
Blood 24 to 96 hours, saliva about 5 days after a single dose and up to 7 days on daily use, urine 3 to 7 days single and 14 to 42 days daily. Its active metabolite nordiazepam, half-life 90 hours, is what stretches the tail.
Does a standard urine drug test detect every benzodiazepine?
No. The class immunoassay reflects diazepam and oxazepam reliably, is variable for bromazepam, catches alprazolam, clonazepam and lorazepam only unreliably, and does not detect etizolam at all. A negative screen is not evidence that nothing is present — only that the assay did not flag one.
Why does daily diazepam stay detectable for six weeks?
Because it accumulates. Diazepam has a half-life of 46 hours and its active metabolite nordiazepam runs 90 hours, so neither clears between two daily doses. On daily dosing nordiazepam builds up nearly sixfold, and the urine window stretches to 14 to 42 days.
Does a benzodiazepine screen detect etizolam?
No. Etizolam is a thienodiazepine sold on the designer market, and the standard class immunoassay does not detect it at all — only a targeted laboratory method will. Its own windows are short: blood 6 to 24 hours, urine 48 to 72 hours after a single dose.
Does a prescription change how long a benzodiazepine is detectable?
No. A prescription changes the legal frame around a positive result, not the pharmacology: the same molecule at the same dose produces the same window. If you take one daily, never stop abruptly — ask your doctor for a taper plan.
Does a negative test mean the benzodiazepine is no longer affecting me?
No. Detection and impairment are different questions. A long-acting benzodiazepine can still affect alertness and reaction time the morning after a dose, while a urine screen can stay positive for weeks after any effect has ended. Neither result describes how you are functioning.
Where these numbers come from
The windows above are the ones built into the Clearhead engine, each tied to a published source rather than to a round number copied between websites. Seven molecules are modelled; zolpidem and the other Z-drugs are deliberately excluded, because they are not benzodiazepines. You can read the wider approach on our methodology page.
Sources referenced by the model: Greenblatt DJ & Abernethy DR — classic benzodiazepine pharmacokinetics, the source of the age and obesity levers · Vindenes V et al., 2019 (nordiazepam in oral fluid; median 132 h at a 1 ng/mL limit of quantification after a single diazepam dose) · Klotz U et al., 1975 (age and diazepam disposition) · Abernethy DR et al., J Pharm Sci 1982 (prolongation of drug half-life in obesity, studied on desmethyldiazepam: 154 h obese vs 57 h lean) · Friedman H et al., 1992; Jongen S & Vermeeren A, 2018; Gorenstein C et al., 1994 (psychomotor and on-road impairment, and tolerance in dependent users) · Front Toxicol 2025, DOI 10.3389/ftox.2025.1639890 (benzodiazepine immunoassay cross-reactivity) · FDA product labels; ASAM 2025 tapering guidance; EUDA reporting on designer benzodiazepines. Reviewed 2 September 2026.