How Long Does Ketamine Stay in Your System in Australia? A Complete Guide
The question of how long ketamine remains detectable in the body is one that concerns both recreational users and patients undergoing legitimate medical treatment. In Australia, the answer depends heavily on the type of drug test used, the frequency of use, and individual metabolic factors. Consequently, understanding these variables is essential for anyone seeking clarity on ketamine detection windows.
The Science of Ketamine Metabolism
First and foremost, you must understand how the body processes ketamine. Ketamine metabolises in the liver through demethylation via the cytochrome P450 system into norketamine, its primary metabolite . The terminal half-life of ketamine ranges between 79 minutes after continuous infusion and 186 minutes after low-dose intravenous administration .
Approximately 95% of ketamine and its metabolites eliminate within the first 24 hours, with 98% excreted via the kidneys and 2% via faeces . However, this rapid elimination does not mean the drug becomes undetectable quickly. As the body breaks ketamine down, it produces norketamine, which can remain detectable longer than ketamine itself .
Detection Windows by Test Type
The detection window varies dramatically depending on the biological sample used for testing.
Urine Testing
Urine testing is the most common method for detecting ketamine. The standard detection time for ketamine in urine is 3–5 days . However, this window can extend significantly depending on usage patterns.
A study examining chronic users found that urine samples remained positive for 22 to 96 days after last use, measured using liquid chromatography-tandem mass spectrometry at a cutoff concentration of 1.0 ng/mL . This prolonged excretion profile requires frequent measurements to guide abstinence treatment .
Blood Testing
Blood tests have the shortest window, generally detecting ketamine for approximately 4 to 24 hours after use . The parent drug clears from the bloodstream quickly because the liver rapidly converts ketamine to norketamine .
An assay targeting 5,6-DHNK, ketamine’s longest-lasting metabolite, can extend plasma detection to roughly 6 to 10 days . However, this specialised testing is typically reserved for forensic or research settings.
Saliva Testing
Saliva testing operates on a similarly short timeline. Ketamine is mostly undetectable in saliva within 4 to 6 hours of use, though it can linger up to 24 to 48 hours .
Australian research conducted through Monash Health evaluated the Securetec DrugWipe 6S Ketamine device. At a cut-off level of 5ng/mL, the device indicated uniformly positive results during acute dosing. At 2 hours post-treatment, the positive detection rate was 85%. By 4 hours post-treatment, the detection rate reduced to 40% .
Hair Testing
Hair follicle testing provides the longest historical window. A standard sample represents approximately three months of use and is generally cited as detecting ketamine up to 90 days . One case report describes detection up to 4 months, though this is best treated as a case-report maximum rather than a typical result .
The Australian Roadside Testing Reality
For Australian drivers, one fact is particularly important: roadside drug testing (RDT) in Australia typically does not test for ketamine . A NSW Parliament submission notes that prescription substances capable of impairment, including benzodiazepines, psychedelics, and ketamine, are not detected on RDTs, highlighting inconsistencies in current policy .
Victorian police similarly do not test for cocaine, ketamine, LSD, or mushrooms . The standard AS/NZS 4760:2019 panels used for oral fluid testing screen for amphetamine-type substances, benzodiazepines, cocaine, methamphetamine, opiates, oxycodone, and cannabis — but not ketamine .
However, this does not mean ketamine use carries no driving risk. HRVic’s harm reduction guidance states that while roadside saliva tests do not look for ketamine, other substances can be detected that might have been cut into your ketamine . More importantly, any driver may be subject to a roadside behavioural impairment test if police suspect impairment .
Factors Affecting Detection Time
Several variables influence how long ketamine remains detectable:
Frequency of use: Chronic or heavy use extends the detection window considerably. The 22–96 day range observed in one study applies specifically to chronic users, not single-dose use .
Dose and route: Higher doses and different routes of administration affect how much ketamine and its metabolites accumulate in the body.
Individual metabolism: The study on chronic users noted large interindividual variation in ketamine metabolism, with K/norketamine ratios varying between 0.33 and 3.06 . This means two people using the same amount could have significantly different detection windows.
Body composition: Size, weight, and overall health influence how the body processes and eliminates ketamine .
Harm Reduction Guidance
For those who use ketamine, Australian harm reduction organisations provide clear guidance. HRVic advises waiting at least 24 hours before driving after ketamine use, noting that taking multiple doses over several hours can lengthen this period .
The organisation also notes that even though the apparent effects of ketamine may wear off after 2 hours, the drug is still active in your system for up to 6–12 hours after use . If redosing, waiting at least 2 hours is recommended .
The Medical Context
In Australia, ketamine has a legitimate medical role. Esketamine nasal spray (Spravato) is available on the Pharmaceutical Benefits Scheme for treatment-resistant depression in adults, subsidised from 1 May 2025 . Patients receiving this treatment must be monitored by a health professional, and the medication is administered under direct supervision .
For patients undergoing ketamine infusion for pain management, South Australian health authorities advise that they should not drive or operate machinery for the rest of the day and should have a responsible adult accompany them home .
Summary
Ketamine detection windows in Australia vary significantly by test type. Urine testing detects ketamine for 3–5 days in standard cases, but chronic users may test positive for 22–96 days. Blood and saliva testing have much shorter windows of approximately 24–48 hours. Hair testing can detect use for up to 90 days or, in rare cases, 4 months.
Standard Australian roadside drug testing does not screen for ketamine, but police can conduct behavioural impairment tests if they suspect a driver is affected. The safest approach remains waiting at least 24 hours after use before driving.