Our new Drug Detection Window Calculator
How long do drugs stay in your system? It's one of the most common questions people ask when researching drug testing. Whether you're concerned about cannabis, cocaine, amphetamines, benzodiazepines or another substance, finding a reliable answer isn't always straightforward.
The reason is simple: there is no single detection time that applies to everyone. How long a drug may be detected depends on the substance, how often it has been used, when it was last taken and the type of drug test being carried out.
To make this information easier to understand, we've just launched our new Drug Detection Window Calculator, a free tool covering more than 40 substances, including alcohol.
What is a drug detection window?
A drug detection window is the period during which a particular drug, or its metabolites, may be detected by a drug test. Different types of drug test have different detection windows:
| Test type | What it generally shows |
| Urine | Use that may have taken place some time before the test, often after the effects have worn off. The most widely used type of drug test. |
| Saliva (oral fluid) | More recent use, with a shorter detection window than urine. |
| Hair | A longer-term history of drug exposure, rather than very recent use. |
| Blood | A relatively short detection window, usually tested in a clinical or laboratory setting. |
This means that asking “How long do drugs stay in your system?” doesn't have one simple answer. A more useful question is: “How long could this particular drug be detected by this particular type of test?”
Our new calculator has been designed to help answer exactly that question.
Introducing the UK Drug Testing Drug Detection Window Calculator
The new calculator makes it quick and easy to explore typical drug detection times. Simply select:
- The substance – from more than 40 drugs, plus alcohol
- How often it is used – one-off or occasional, or regular or heavy
- When it was last taken – anywhere from 1 hour to 1 month ago
The calculator then shows whether that substance is typically likely to still be detectable on a urine test, a saliva test, a hair test and a blood test.
Underneath the calculator, you'll also find a full reference table of typical detection times for every substance, showing figures for both one-off use and regular or heavy use.
Use the Drug Detection Window Calculator
Why does how often you use a drug matter?
One of the biggest reasons drug detection times vary is frequency of use. Someone who has used a substance once or occasionally may have a very different detection window from someone who uses it regularly or heavily.
That's why our calculator distinguishes between one-off or occasional use and regular or heavy use. This is particularly important for substances such as cannabis. Just because you've read that cannabis can be detected for a particular number of days, you shouldn't assume that figure will apply to you. Your pattern of use can make a significant difference.
How long do drugs stay in urine?
Urine drug testing is one of the most commonly used forms of drug testing. Drugs and their metabolites can often remain detectable in urine after the effects of the drug have worn off. However, detection times vary considerably between substances and between individuals, and regular or heavy use can produce a longer detection window than occasional use.
The cut-off level of the test is another important factor. A drug test doesn't simply ask whether any trace of a substance exists; it's designed to identify a drug or metabolite above a specified concentration. This is why published detection times should always be regarded as estimates rather than guarantees.
For broad coverage from a single sample, our 13 panel ultra sensitive urine drug test cup screens for 13 drugs and uses lower cut-off levels than many standard urine tests:
How long do drugs stay in saliva?
Saliva, or oral fluid, testing generally has a shorter detection window than urine testing. This makes saliva testing particularly useful when the aim is to identify more recent drug use. However, the exact detection period still varies depending on the substance, the individual and the test being used.
This is also why a person could potentially get different results from a saliva test and a urine test taken around the same time. The tests are looking at different specimens and have different detection characteristics.
Our ALLTEST 13 panel saliva test screens for 12 drugs plus alcohol from one oral fluid sample, making it a popular choice for workplace saliva testing:
How long do drugs stay in hair?
Hair testing works differently from urine and saliva testing. Rather than focusing on very recent drug use, a hair drug test can provide information about drug exposure over a considerably longer period. It also takes several days for drugs to become incorporated into newly grown hair, so hair testing isn't suited to detecting very recent use.
The detection period can depend on factors including hair growth, the length of the sample and the testing methodology. Hair testing is therefore not directly comparable with a urine or saliva test.
How long do drugs stay in blood?
Blood testing generally has a relatively short detection window compared with hair testing, and is usually carried out in a clinical or laboratory setting.
However, there is considerable variation between different substances, and blood testing shouldn't be treated as interchangeable with urine, saliva or hair testing. The type of test being used is always important when considering how long a drug may be detectable.
How long does cannabis stay in your system?
Cannabis is one of the substances people most commonly search for when looking up drug detection times. However, there isn't one number that applies to everyone. The detection window can be affected by whether cannabis has been used once, occasionally or regularly over a prolonged period.
The type of test also makes a major difference. A urine test and a saliva test don't have the same detection window, which is why simply searching “how long does cannabis stay in your system?” without specifying the type of test can produce confusing or contradictory answers. Our guide to cannabis saliva detection times explains why oral fluid tests focus on more recent use.
Test sensitivity plays a part too. Ultra sensitive drug tests use lower cut-off levels, so they can pick up smaller concentrations of a substance than standard tests. Our calculator takes both frequency of use and type of test into account when providing its typical detection information.
What does the cut-off level of a drug test mean?
You may sometimes see drug tests described as having different cut-off levels. The cut-off is the concentration at which a test is designed to identify a substance as positive.
This matters because detection is not simply a case of asking whether the smallest possible trace of a drug remains in the body. A test result depends on the concentration detected and the cut-off used by that particular test, which is one reason why detection-time figures found online can vary.
You can check the cut-off levels for our kits in our guide to drug test detection times and cut-off levels.
Why can't a drug detection calculator guarantee your test result?
This is an important point. Our Drug Detection Window Calculator provides typical estimates, not guarantees. It cannot predict with certainty whether an individual will receive a positive or negative result on a particular drug test.
Detection times can vary according to:
- The substance used
- The amount taken
- How frequently it is used
- Individual metabolism
- Body weight
- Hydration
- The type of specimen being tested
- The sensitivity and cut-off level of the test
The calculator itself makes clear that individual results vary and that it cannot predict the result of a specific test.
Can you use the calculator to find out if you will pass a drug test?
No. The calculator is intended to help you understand typical drug detection windows. It should not be used as a guarantee that someone will pass or fail a specific test.
If you have an upcoming drug test, find out what type of test is being used and, where possible, which substances and cut-off levels are being tested. If the test is being carried out for employment, legal, licensing or another formal purpose, you should follow the requirements of the organisation conducting the test.
If you take prescription or over-the-counter medication, make sure you tell whoever is carrying out the test, as some medicines can affect screening results.
How employers can use the calculator
For employers, the calculator is a handy way to think through which type of test best suits the question you're trying to answer:
- Recent use: workplace saliva drug test kits focus on more recent use, which suits for-cause and post-incident testing.
- A wider window: workplace urine drug test kits can detect many substances for longer, which suits pre-employment and random testing.
- Drugs and alcohol together: workplace drug and alcohol test kits screen for both from a single test.
Whichever you choose, remember that on-site kits are screening tests. Any non-negative result should be confirmed by an accredited laboratory before any decisions are made, so it's worth keeping a confirmation pack on site:
Not sure which kit is right for your workplace? Our workplace drug test quiz can help you narrow down the options.
Why we created the Drug Detection Window Calculator
There is a huge amount of information about drug testing online, but it isn't always easy to interpret. One website may say a drug is detectable for a certain number of days, while another gives a different figure. Often, both may be referring to different types of drug test, different patterns of use or different testing cut-offs.
We wanted to make it easier to understand the context behind drug detection times. Our calculator brings the key variables together in one place, allowing you to select the substance, frequency of use and time since last use, and then see typical detection information for each testing method.
Try the new Drug Detection Window Calculator
If you're researching drug testing and want to understand how long a particular substance may be detectable, give our new calculator a try. Select the substance, tell us how frequently it was used and when it was last taken, and the calculator will show typical detection information for urine, saliva, hair and blood testing.
Remember, detection times are estimates: drug detection is not an exact countdown. The same substance can have different detection windows in different people, and the same person may have different detection windows depending on the type of test being used. Our calculator is a guide to typical detection windows, not a prediction of an individual test result. If you need advice about a specific test, the organisation conducting it or an appropriately qualified professional should be able to advise you on the testing method being used.
UK Drug Testing has been run by UK doctors since 1998, providing drug and alcohol testing kits to employers and individuals across the UK.
The information in this article and in our Drug Detection Window Calculator is provided for general educational purposes only and does not constitute medical or legal advice. Detection times are typical estimates and cannot predict the result of any individual drug test.
Point-of-care drug test kits are screening tests only. Any non-negative result should be confirmed using an accredited laboratory confirmation method before any decisions or actions are taken based on the result.
If you take prescribed or over-the-counter medication, tell whoever is carrying out the test. If you have concerns about your own or someone else's drug use, please speak to a healthcare professional or a dedicated drug and alcohol support service.