Ketamine has an elimination half-life of 2 to 4 hours, meaning most of the drug clears your bloodstream within about 12 to 24 hours. But traces of ketamine and its breakdown products can show up on certain tests for much longer, from a few days in saliva to several months in hair. How long it lingers depends on the type of test, how much you took, and how often you used it.
How Your Body Breaks Down Ketamine
Your liver does the heavy lifting. A family of enzymes, primarily one called CYP3A4, converts ketamine into a compound called norketamine. This metabolite is active (it still has some effects) and sticks around longer than ketamine itself, which is why drug tests often screen for norketamine rather than the parent drug alone.
After a single dose, ketamine’s blood concentration drops by half roughly every 2.5 hours. Within 10 to 12 hours, most of the ketamine itself has been processed. Norketamine takes longer to clear because it goes through additional rounds of metabolism before your kidneys excrete it in urine.
Detection Windows by Test Type
Different biological samples hold onto ketamine for very different lengths of time. Here’s what the research shows for each:
- Blood: Ketamine is detectable for up to about 3 days, though tests are most reliable within the first 24 hours after use.
- Saliva: Oral fluid tests can pick up ketamine for roughly 24 to 72 hours, depending on the sensitivity of the assay.
- Urine: Using highly sensitive lab techniques, researchers have confirmed ketamine in urine for up to 5 days and norketamine for up to 6 days after a dose. With less sensitive screening methods, the window is shorter, typically 2 to 4 days for occasional use.
- Hair: Hair follicle testing has the longest reach. One case study estimated ketamine’s half-life in hair at just under one month, and the drug remained detectable more than 4 months after the last dose. Full clearance to undetectable levels may take around 7 months, which is comparable to the timeline seen with amphetamines and methamphetamine.
Does Ketamine Show Up on Standard Drug Tests?
No. Standard 5-panel and 10-panel drug screens, the kind most employers use, do not test for ketamine. Those panels typically cover cannabis, cocaine, opioids, amphetamines, and PCP (with the 10-panel adding benzodiazepines, barbiturates, and a few others). Ketamine will only appear if a test is specifically ordered to look for it. Specialized panels used in some clinical, forensic, or military settings may include ketamine, but routine workplace screening does not.
Chronic Use Extends the Timeline
All the detection windows above assume relatively infrequent use. If you’ve been using ketamine regularly, the drug and its metabolites accumulate in body tissues, particularly fat. This creates a reservoir that slowly releases back into the bloodstream over days or weeks after you stop. Chronic users can test positive on urine screens for considerably longer than the 5- to 6-day window seen after a single dose. Some sources cite urine detection windows of up to 30 days for heavy, repeated use, though that figure represents an upper bound rather than the norm.
Factors That Speed Up or Slow Down Clearance
Several variables influence how quickly your body eliminates ketamine:
Age. The liver enzymes responsible for breaking down ketamine become less efficient as you get older. Older adults generally clear the drug more slowly than younger people.
Body composition. Ketamine is lipophilic, meaning it dissolves into fat tissue. People with higher body fat percentages may store more of the drug, leading to a longer elimination tail. That said, BMI alone doesn’t perfectly predict clearance speed, because body fat distribution and individual metabolic rates vary widely.
Liver function. Since nearly all ketamine metabolism happens in the liver, any condition that impairs liver function (chronic liver disease, cirrhosis, heavy alcohol use) will slow clearance significantly.
Other medications. Drugs that inhibit or compete for the same liver enzymes can change how fast ketamine is processed. Certain antifungal medications, for example, slow down the main enzyme involved, which could keep ketamine in your system longer.
How the Route of Administration Matters
The way ketamine enters your body affects how much of it actually reaches your bloodstream, which in turn affects how long it’s detectable. Intravenous ketamine hits peak blood levels almost immediately and has 100% bioavailability, meaning every bit of the dose enters circulation. Intramuscular injection isn’t far behind at about 93% bioavailability, with peak levels in 5 to 30 minutes.
Oral ketamine is a different story. Because it passes through the liver before reaching general circulation (a process called first-pass metabolism), only about 16% to 29% of the dose makes it into the bloodstream. Intranasal ketamine, the route used by the prescription nasal spray for depression, falls in between at roughly 45% to 50% bioavailability. Lower bioavailability generally means lower peak blood concentrations and a shorter detection window, though the total elimination timeline doesn’t change dramatically because the half-life remains the same regardless of how the drug got in.
For someone receiving low-dose ketamine infusions in a clinical setting, the amount administered is typically far below what recreational users take. This means both the intensity and duration of detectability tend to be shorter after a single therapeutic session compared to a recreational dose.