How long does ketamine stay in your system?

How long it’s possible for ketamine to remain in your body, including your blood, urine and saliva, after you’ve taken it.

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Ketamine, also known as ‘Ket’, ‘Special K’ or simply ‘K’, is a powerful hallucinogenic drug. Ketamine usually comes in powder form which can be snorted or swallowed as a tablet, but it can also be injected in liquid form. The drug was originally designed to be used in healthcare or veterinary settings to provide pain relief during human and animal operations. As such, it also has strong anaesthetic effects.

In this blog we’ll explore how long ketamine can be detected in saliva, blood, urine and hair after it’s been consumed, as well as the factors that can affect this. We’ll also look at how long the effects of ketamine can last and what ketamine withdrawal feels like.

How long does ketamine stay in your body?

Ketamine has a half-life of around 2.5 to 3 hours in adults. This is the time it takes for the ketamine in your body to reduce by half. When the amount of ketamine in your system reduces, you may start having a 'comedown'. To avoid the feelings of a comedown, some people take more of the drug to keep up with the euphoric state they were in before.

how long does ketamine stay in your system

While 2.5 to 3 hours may seem to be a short amount of time, ketamine drug testing can detect traces of ketamine in your system for much longer.

Ketamine can be detected in your body using a number of tests:

  • Saliva test – saliva tests can detect ketamine for up to 24 hours after you’ve taken it
  • Blood test – a blood test can show ketamine in your system for up to 3 days after you've taken it, but it's most effective within the first 24 hours
  • Urine test – ketamine can be detected in your urine for up to 14 days after you last used it. However, some studies suggest that it’s possible for ket to be detected in your urine for as long as 30 days after you took it
  • Hair test – traces of ketamine can remain in your hair and hair follicles for up to 4 months after a single usage

What factors affect how long ketamine stays in your system?

There are lots of different factors that can affect how long ketamine stays in your system.

Age and overall health

Young, healthy people are able to clear ketamine from their system quicker than older people, because their metabolisms are generally quicker.

Levels of hydration

Most ketamine leaves the body in your urine so if you’re well-hydrated and therefore urinating more often, the ketamine will leave your body quicker.


People with a faster metabolism are able to break down and eliminate drugs like ketamine faster than someone who has a slower metabolism.

Kidney and liver function

Your kidneys and liver are responsible for flushing ket out of your system. However, if your kidney or liver functioning is impaired for some reason, this can mean it takes longer to get rid of the ketamine.

Body mass

Having a higher body mass can mean that you’re able to metabolise ketamine quicker than someone with a smaller body mass. This is because the amount of ketamine you have taken represents a smaller proportion of your overall body mass. This means that those with higher body masses can get rid of ketamine quicker.

Ketamine dose

The higher the dose of ketamine, the harder your body will have to work to get rid of it and therefore, the longer it will take.

How frequently you take ket

If you regularly abuse ketamine, you may end up consuming another dose before the last one has fully left your system. This can cause a build-up in your body, meaning it takes longer to fully eliminate the drug.

Whether you mix ket with other drugs

If you take ketamine alongside other drugs, this means that your body has to break down all of these substances together, which can make the process take longer.

How long do the effects of ket last?

When it’s snorted, the effects of ketamine are usually felt after around 10 to 15 minutes. When it’s taken as a tablet, the onset of its effects can take slightly longer – around 20 minutes. When ketamine is injected directly into the bloodstream, the effects can be felt almost immediately.

The effects of ketamine can then last anywhere between 30 minutes to 1 hour, depending on how much you’ve taken, with high doses causing longer effects.

Effects can include:

  • Feelings of euphoria, relaxation and pleasure
  • Feeling detached from your body and surroundings
  • Hallucinations
  • Altered perception of space and time
  • Prevent you feeling pain

Withdrawing from ketamine

If you've been taking ketamine regularly, your body will be used to having this drug in its system. Therefore, when you stop taking ketamine or can't get hold of it, you’ll likely experience a series of unpleasant withdrawal symptoms.

These can include mental health symptoms such as severe depression and anxiety, aggression, irritability, paranoia, psychosis, panic attacks, insomnia and suicidal thoughts.

Physical symptoms of ketamine withdrawal can include stomach cramps, vision and hearing problems, bladder pain, sweating, increased heart rate and intense cravings for ket.

Page clinically reviewed by Dr Patrick Mbaya (MB ChB, MSc, MD, FRCPsych, Cert. Psychopharmacology), Lead Consultant for Addictions at Priory Hospital Altrincham.

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