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Drug testing

What is a drug test?

What are the limitations of drug tests?

What can affect how long a drug stays in the body?

Types of drug tests

How to pass a drug test

Drug testing kits and breathalysers

Can people be forced to have a drug test?

What is a drug test?

Drug testing looks for traces of drugs in the body using samples of urine, breath, hair, saliva, or sweat.

Drug tests detect whether you are under the influence of alcohol or whether you have taken drugs recently. There are various methods of drug testing including urine, blood, breath, hair, saliva and sweat. Hair and sweat testing are generally not used in Australia1.

Testing may be used by a range of organisations including:

  • Police to detect if a driver is under the influence of alcohol while driving or has taken drugs recently.
  • Workplaces to check for past use of illicit drugs and blood alcohol concentration while working.
  • Sporting bodies to detect drugs that are not permitted while competing in certain competitions. 
  • Drug treatment services to inform medical decisions, usually on whether pharmacotherapy should be continued.
  • Judicial settings to inform legal decisions such as in custody cases. 
  • Some non-government schools to detect use of illicit drugs.

What are the limitations of drug tests?

Drug tests can't tell exactly how much of a drug was used or exactly when it was used. Drug tests also don't measure impairment, apart from alcohol breath testing. There is strong evidence to support the position that a blood alcohol content (BAC) of .05 or higher indicates impairment1.

Laboratory testing is necessary to confirm any positive test to Australian standards8 and is generally more accurate than 'point-of-collection testing' (POCT), but it's not always exact. POCT devices provide more timely results, but laboratory analysis can better differentiate illicit from prescription drug use1.

What can affect how long a drug stays in the body?

Drugs are metabolised (processed) by people differently. Results of drug tests are always unique to the person who was tested. This means that two people could take the same amount of a drug, at the same time, and have the same type of drug test, but have different test results. Some factors that affect how long a drug stays in the body are:

  • The strength of the drug
  • How much of it was used
  • How it was used (e.g. drunk, smoked, injected)
  • How often it was used
  • What other drugs were taken
  • Tolerance to the drug
  • Gender and age
  • Overall health and wellbeing
  • Metabolism


The different types of drug tests


What they test for: Alcohol

Method/process: Blow into a hand held device.

Used by: Police, workplaces.

Detection time after last use: It takes approximately 1 hour for the body to break down each standard drink2.


What they test for: Can test for all prescription and illicit drugs, including some forms of synthetic cannabis. Tests can be modified to detect particular substances.

Method/process: Urinate into a container. The urine will be tested using a dipstick. If the test is positive the urine sample will be sent to a laboratory for more testing.

Used by: Workplaces, drug treatment centres, sporting bodies.

Detection time after last use: Cannabis up to 10 days (infrequent use) or 30 days or longer (frequent use), opiates 2 to 4 days, amphetamines 2 to 5 days, cocaine 2 to 3 days, benzodiazepines up to 2 weeks1.


What they test for: Can test for all illicit and prescription drugs. Tests can be modified to detect particular substances. Sometimes used instead of or to confirm a breath test for alcohol.  

Method/process: A blood sample will be taken from a finger prick, or from a vein in the arm or hand, using a needle. The blood sample will be tested by a laboratory.

Used by: Police, drug treatment centres, sporting bodies.

Detection time after last use: Cannabis 20 to 36 hours, amphetamines 4 to 8 hours, cocaine 40 to 90 minutes, Xanax® 6 to 20 hours3.


What they test for: Can test for use of cannabis, methamphetamines, MDMA (ecstasy), cocaine, opiates and some benzodiazepines.

Method/process: An absorbent collector is put in the mouth or on the tongue.

Used by: Police, workplaces.

Detection time after last use: Cannabis several hours after last use and is dependent upon the potency, amount used and the individual's metabolism, methamphetamines approximately 24 hours, MDMA (ecstasy) approximately 24 hours1. Opiates approximately 0-3 days.10 Detection time for benzodiazepines is currently unknown.


What they test for: Can test for all illicit drug use and some prescription drugs.

Method/process: Approximately 40 to 50 strands of hair will be cut from the scalp line at the crown of the head. The hair sample will be tested by a laboratory.

Used by: Sporting bodies, justice settings. 

Detection time after last use: Can detect past use up to a few months, and can therefore test for chronic use1.

How to pass a drug test

Other than not taking drugs, the only sure way to pass a drug test (i.e. to test negative) is to make sure the body has metabolised (processed) all of the drug(s) taken. For example, making sure enough time has passed for the body to process the alcohol that has been drunk before driving.

Getting a negative drug test result means that:

  • The person has not taken the drug(s) being tested for, or
  • The body has metabolised all traces of the drug(s), or
  • The test wasn't accurate or sensitive enough to find the traces of the drug(s).


Taking substances such as aspirin, niacin, bleach, vinegar, cranberry juice or goldenseal to mask or disguise drug use will not give a negative test result and may cause harmful effects. There are products sold that claim they can help a person to pass a drug test. However, there's no reliable evidence that any of these actually work.

There's no guaranteed way to get rid of a drug in the body other than waiting for the body to process it. If a person knows they will be drug tested and are worried, then it's best not to use drugs. Help and support is available.

Can drinking lots of water help to pass a drug test?

Drinking lots of water does not guarantee a clean drug test. Most urine tests check for dilution (too much water) and may reject the results.

Drinking too much water is not advised because the body might not be able to deal with it, which is called 'water intoxication' or 'water overdose'. This can cause headaches, blurred vision, cramps and eventually convulsions6.

What if more than one drug is taken?

If more than one drug is taken at a time (including alcohol), the body may take longer to process them than if only one had been taken. Most drugs will stay in the body for at least 24 to 48 hours, so they don't need to be taken at exactly the same time to have an effect on each other.

Even if a person does not feel the effects of the drugs anymore, they can still be in the body.

What is a false positive?

A false positive is a test result that is positive for a drug that has not been taken. It's false because the result is incorrect. A false positive usually means that the test wasn't sensitive or accurate enough to be able to tell the difference between two drugs. For example, a person may have taken a prescription drug, but this was confused by the test with an illegal drug7. If prescription drugs are being taken, it is appropriate to inform the employer about this prior to being drug tested at work.

Passive cannabis smoking

Traces of cannabis can be found in body fluids by inhaling someone else's cannabis smoke (called passive cannabis smoking). However, testing companies often say that the concentrations of these traces would be too low to give a positive test result for cannabis8.

Why does cannabis stay in the body for so long?

Cannabis is stored in the body differently to other drugs. If cannabis is used once, the body can get rid of it fairly quickly (within a couple of hours). However, regular use of cannabis causes THC (the active ingredient in cannabis) to accumulate in the body's fat cells. This can take a long time to be broken down and metabolised7.

Drug testing kits and breathalysers

Do home drug testing kits work?

Drug testing kits can be bought online and from some pharmacies. There are different types of kits, which test for a range of illicit drugs. These kits are often promoted to parents as a way of finding out if their children have used drugs.

The reliability and quality of these testing kits has improved greatly over the last few years but most of the kits are still limited. For example, they can only detect use of common illicit drugs like cannabis and amphetamines, and not new psychoactive substances like synthetic cannabis and NBOMes.

There can also be issues with actually conducting the tests. For example, if a parent wanted to test their child, who didn't want to be tested and denied taking drugs, their relationship could be seriously affected, creating a situation of mistrust and suspicion. It is always better to talk with the child9. Find further information on The Other Talk website.

Pub and home breathalysers

Many pubs and bars have breathalysers available for patrons to use. There are also a number of personal breathalysers available for purchase, for example at petrol stations. These breathalysers should only be used as a general guide of BAC levels. They are not recommended for calculating if a person can drive or not and test results cannot be used in a court of law or to question a result obtained through a police breathalyser.

Can people be forced to have a drug test?

Drug testing in workplaces is usually used when there are safety issues related to the job, such as driving a vehicle or operating machinery. If a person is employed in this type of work, they could be asked to have a drug test as a requirement of the job. There will probably be consequences if the person refuses, such as losing their job.

If a person is driving, anywhere in Australia, and refuses a random roadside breath or drug test when they are asked to have one by the police, they can be fined or lose their licence.

Australian public schools don't drug test their students. However, drug testing of students in non-government schools may be part of the school's drug policy.

Further information

Reducing the risks



ADF SEARCH – Find further credible research and information on drug testing.

ADIN – Find other credible websites and apps on alcohol.


1. South Australian Government. (n.d.). Drug Driving FAQs.

2. Better Health Channel. (2009). Drink driving.

3. Medline Plus. (2014). Toxicology screen.

4. Lab Tests Online.(2013). Drugs of abuse testing.

5. Medline Plus. (2014). Urine drug screen.

6. North Carolina Judicial College. (2010). Adulteration and dilution checks.

7. National Centre for Education, Treatment and Addiction. (NCETA). (2011). Workplace drug and alcohol testing.

8. Lewis, J. (nd). Bulletin 7: Clinical and medico-legal implications of drug testing for cannabis.

9. Rosenbaum, C., Carreiro, S., & Babu, K. (2012). Here today, gone tomorrow…and back again? A review of herbal marijuana alternatives (K2, Spice), synthetic cathinones (bath salts), kratom, Salvia divinorum, methoxetamine, and piperazines. Journal of Medical Toxicology, 8(1), 15–32. 

10. Australian National Council on Drugs. (2013). Positon Paper - Drug Testing.

Last updated: 7 June 2016

Information you heard is intended as a general guide only. This audio is copyrighted by the Australian Drug Foundation. Visit for more