Ketamine sits in two very different worlds. It is an established anaesthetic with legitimate uses in human and veterinary medicine, yet it is also used outside medical settings as a dissociative drug. More recently, ketamine and its related compound esketamine have attracted considerable attention because of research into treatment-resistant depression.

Those contexts are easy to blur. They should not be.

A measured dose administered in a clinical environment, with a known formulation and appropriate monitoring, is not equivalent to taking a powder obtained through an unregulated supply chain. The active substance may be the same in some cases, but the certainty about identity, concentration, dose, medical suitability and monitoring is not.

Understanding that distinction makes the rest of the ketamine discussion considerably clearer.

What is ketamine?

Ketamine is a dissociative anaesthetic and analgesic. The Advisory Council on the Misuse of Drugs describes it as a medicine widely used for anaesthesia and pain relief in human and veterinary practice.

It produces anaesthesia differently from many conventional sedatives. Rather than simply making someone sleepy, ketamine can substantially alter awareness, perception, sensation and the person’s relationship with their surroundings.

The molecule exists in two mirror-image forms. One of these, S-ketamine or esketamine, has greater biological activity and is also available in a licensed nasal formulation for certain patients with treatment-resistant depression.

The ACMD’s 2026 review of ketamine gives the most detailed recent UK assessment of its legitimate uses and the harms associated with non-medical use.

How does ketamine affect perception and awareness?

Ketamine is generally described as a dissociative drug because it can separate aspects of perception that normally feel connected. Someone may feel detached from their body, surroundings or immediate experience. Time and distance can feel distorted. Coordination and judgement may also deteriorate.

The intensity is not fixed. Dose, route of administration, tolerance, individual physiology and other substances can all change the experience.

At lower levels, a person may remain able to communicate while feeling noticeably detached or impaired. With greater intoxication, awareness of the surrounding environment can become profoundly disrupted.

This matters beyond the subjective experience. Reduced coordination and altered pain perception can make falls or injuries more likely to go unnoticed. Someone who appears awake may still be poorly equipped to recognise danger or make sensible decisions.

Our supporting guide to ketamine effects examines the short-term physical and psychological effects in more detail.

Short-term ketamine risks are not limited to dissociation

Confusion, nausea, vomiting, dizziness, impaired coordination and memory disruption can occur. Cardiovascular changes are also relevant because ketamine can increase heart rate and blood pressure.

The surrounding circumstances often matter as much as a single effect. A person who is heavily impaired near traffic, water, stairs or other hazards faces a different risk from someone receiving a controlled medicine while being monitored clinically.

Combining ketamine with other substances can make the situation less predictable. Alcohol and other sedating drugs are particularly important because combined impairment can become substantially greater than the person expects.

See our separate evidence summaries on ketamine and alcohol and ketamine with benzodiazepines.

The distinction between medical ketamine and illicit ketamine matters

Medical use involves controls that are easily overlooked when ketamine is discussed as though it were a single, uniform product.

Clinicians can work with a known formulation, measured dose and documented medical history. They can consider other medicines, cardiovascular conditions, psychiatric history and the reason treatment is being given. Monitoring is available if an adverse reaction occurs.

An illicit powder provides none of those assurances.

Colour, texture or crystal appearance cannot establish that a substance is ketamine. Even when ketamine is present, appearance cannot reveal concentration or identify other substances that may also be present.

This is why identifying an unknown substance from a photograph or description is unreliable. Our guide to identifying ketamine by appearance explains those limitations.

What about ketamine for depression?

This is one of the areas where online discussion most often loses important context.

Research has found that ketamine can produce relatively rapid antidepressant effects in some people, particularly in treatment-resistant depression. That has created justified scientific interest, but it has also encouraged a misleading leap from “ketamine is being studied as a treatment” to “taking ketamine treats depression”. Those statements are not equivalent.

Ketamine itself has long been licensed as an anaesthetic. Esketamine nasal spray has a marketing authorisation for treatment-resistant depression in specified circumstances.

NICE has nevertheless taken a cautious position. Its January 2026 surveillance work found that important uncertainties remain around intravenous ketamine, including the durability of benefit, comparisons with established treatments and long-term outcomes.

The NICE review of ketamine evidence in treatment-resistant depression states that current evidence does not establish intravenous ketamine as equivalent or superior to electroconvulsive therapy, and significant questions remain about long-term effects.

That uncertainty is clinically important. Rapid improvement after a treatment does not by itself tell us how durable the benefit will be, how repeated treatment should be managed, or what longer-term harms might emerge.

Our dedicated page on medical ketamine treatment in the UK separates clinical treatment from non-medical use more fully.

Ketamine bladder damage is one of the clearest long-term warning signs

Frequent ketamine use has a particularly well-recognised association with urinary tract damage.

People may first notice that they need to urinate far more frequently than before. Urgency, pain when passing urine, pelvic or lower abdominal discomfort and blood in the urine can follow.

These symptoms should not be normalised simply because they are known among regular ketamine users.

Repeated exposure can damage and inflame the bladder. As the condition progresses, bladder capacity may shrink substantially. The upper urinary tract and kidneys can also become involved.

The ACMD’s 2026 review warns that chronic urinary damage can become severe and that recovery may be incomplete, particularly where damage is advanced before use stops or medical care is obtained.

This has an important practical consequence: waiting for urinary symptoms to become unbearable is not a sensible way to judge severity. Persistent frequency, pain, blood in the urine or worsening urinary control warrants medical assessment.

Our guide to ketamine bladder damage and ketamine-induced cystitis covers the symptoms and progression in greater detail.

Abdominal, liver and bile-duct problems also occur

Bladder injury receives much of the attention, but chronic ketamine harm is not confined to the urinary system.

The ACMD review describes gastrointestinal and hepatobiliary complications associated with heavier and prolonged use. Severe abdominal pain is sometimes called “K cramps” in informal discussion.

The casual label can be misleading. Intense or recurrent abdominal pain is not something that can safely be assumed to be a harmless, temporary feature of ketamine use.

Where abdominal pain is severe, persistent or accompanied by other concerning symptoms, medical evaluation is appropriate.

Can people become dependent on ketamine?

Yes.

Dependence does not occur in every person who uses ketamine, but repeated use can produce tolerance. The amount that once produced a particular effect may feel less effective over time, which can lead to escalation.

At that point the pattern of use can change quickly. What began as intermittent use may become frequent or daily use, sometimes despite urinary symptoms, financial problems or disruption to work and relationships.

The ACMD’s updated assessment describes increasing recognition of ketamine use disorder among people using high amounts regularly.

Our guide to ketamine dependence and addiction looks at tolerance, compulsive use and signs that the pattern has moved beyond occasional consumption.

What does ketamine withdrawal look like?

Stopping after frequent use can be difficult even though ketamine withdrawal does not always resemble withdrawal from alcohol, opioids or benzodiazepines.

Craving can be prominent. Low mood, anxiety, irritability, restlessness and sleep disturbance may also occur.

One problem is that the evidence base for treating ketamine withdrawal is much smaller than it is for several other commonly used drugs. The ACMD notes that evidence for specific withdrawal management remains limited.

That should encourage caution rather than improvised certainty. A person who has been using heavily, is struggling to stop or has significant physical or psychological symptoms may benefit from professional drug and alcohol treatment support.

See our detailed guide to ketamine withdrawal.

How long do ketamine effects last?

There is no universal duration.

The route used, amount, individual metabolism, tolerance and other substances all influence onset and duration. The strongest subjective effects may disappear before judgement, coordination or attention have fully returned to normal.

This distinction is important for activities such as driving. Feeling less intoxicated is not the same as being unimpaired.

Our guide to how long ketamine lasts separates duration of noticeable effects from residual impairment.

Is ketamine legal in the UK?

Ketamine is a Class B controlled drug under the Misuse of Drugs Act 1971.

The government asked the Advisory Council on the Misuse of Drugs to reassess ketamine in 2025 amid concern about increasing use and health harms. The ACMD published its updated assessment on 28 January 2026 and recommended that ketamine remain Class B rather than move to Class A.

The Council’s reasoning is useful. It did not conclude that ketamine was harmless. Quite the opposite: its report describes significant and increasing harms. It concluded that reclassification alone was unlikely to provide the most effective response and recommended a broader approach involving prevention, treatment and improved professional awareness.

GOV.UK currently states that possession of a Class B drug can carry a maximum penalty of five years’ imprisonment, an unlimited fine, or both. Supply or production can carry substantially more severe penalties.

Legal medical possession and use under the controlled-drug framework are different from illicit possession and supply.

See our full guide to ketamine law in the UK, or check the current GOV.UK drug classification and penalties guidance.

Why the 2026 UK review matters

The latest ACMD review changes the conversation in an important way.

Concern about ketamine is no longer centred only on occasional recreational intoxication. UK experts are increasingly dealing with people who have developed significant dependence, urinary damage and other chronic complications.

The report also notes barriers to care. Shame, stigma and limited professional familiarity with ketamine-related harms can delay diagnosis or treatment.

That makes honest disclosure useful in healthcare settings. If somebody with persistent urinary or abdominal symptoms uses ketamine regularly, telling the clinician may substantially change what they consider.

When ketamine symptoms need medical attention

Urinary pain, increasingly frequent urination, blood in the urine, severe lower abdominal pain or loss of bladder control should not be dismissed simply because ketamine use is continuing.

Emergency help is appropriate when someone is unconscious, cannot be properly roused, is having a seizure, has severe breathing difficulty or otherwise appears seriously unwell after taking a substance.

When the product came from an illicit or unregulated source, it is useful to tell healthcare staff what it was believed to be while making clear that the identity is uncertain.

Our emergency help page gives the relevant UK emergency information.

What readers should take from the evidence

Ketamine is neither simply a dangerous street drug nor simply a promising medical treatment. Both descriptions leave out too much.

It is a useful medicine with established anaesthetic applications and genuine therapeutic research behind it. It is also a drug capable of causing dependence and significant chronic injury when used repeatedly outside controlled medical settings.

The urinary complications deserve particular attention because early symptoms can be easy to minimise. They are not trivial warning signs.

Research into depression is important, but it does not make self-medication equivalent to treatment. Clinical ketamine involves screening, known formulations, dose control and monitoring. Illicit supply does not provide those safeguards.

Ketamine: Effects, Risks, Medical Use and UK Law