What this test measures
Ketamine is a dissociative anaesthetic developed in the 1960s that blocks NMDA glutamate receptors. It is widely used in operating theatres, pain medicine, and lower-resource emergency rooms because it preserves airway reflexes. Off-label, it is used by psychiatrists for treatment-resistant depression. Recreationally — known as "K" or "Special K" — it is abused for its hallucinogenic dissociative effects. The serum assay quantifies ketamine and its main metabolite norketamine in blood.
Ketamine has a short plasma half-life of 2–3 hours and is rapidly distributed into tissues, so blood levels fall quickly after the last dose. Most clinical labs use LC-MS/MS for the definitive assay; urine immunoassay drug screens may not reliably detect it and a confirmatory serum test is often needed.
Why it matters
A serum ketamine level is requested in three main settings. First, in the emergency department when a patient presents with dissociation, nystagmus, hypertension, tachycardia, or unexplained altered mental status — particularly young adults at nightclubs or festivals. Second, in suspected drug-facilitated sexual assault, where a rapid blood sample is critical because ketamine clears within hours. Third, when monitoring therapeutic ketamine infusions in operating rooms or pain clinics.
In India, recreational ketamine use is rising in urban club scenes, and addiction medicine specialists increasingly screen for it in psychiatric admissions. Chronic ketamine abuse is linked to a distinctive cystitis ("ketamine bladder") and cognitive impairment — so confirming the diagnosis matters for treatment planning.
How to prepare
No fasting is required. In suspected intoxication or drug-facilitated assault, the sample is drawn as soon as possible because ketamine clears the blood within 8–12 hours. Chain-of-custody documentation is essential for any medico-legal submission. For monitoring of therapeutic infusions, the timing is set by the anaesthesia or pain team.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Ketamine (ng/mL)[1][2] | Not detected | Ketamine is not normally present in serum. A "not detected" result rules out recent use within the past 8–12 hours. | 50–200 ng/mL: sub-anaesthetic / sub-dissociative levels (similar to depression therapy infusions). 200–1000 ng/mL: dissociative anaesthetic range; consistent with recreational use or low-dose anaesthesia. > 1000 ng/mL: deep anaesthetic levels; risk of unconsciousness, respiratory depression, and aspiration. |
Approximate serum ketamine ranges
| Range (ng/mL) | Clinical context |
|---|---|
| Not detected | No recent exposure |
| 50 – 200 | Sub-dissociative dose; depression infusion or analgesia |
| 200 – 1000 | Dissociative anaesthesia; consistent with recreational use |
| 1000 – 2500 | Deep anaesthesia; significant impairment |
| > 2500 | Severe overdose; risk of respiratory depression |
Frequently asked questions
How long is ketamine detectable in blood?
Ketamine has a short half-life (2–3 hours). In blood it is usually detectable for 8–12 hours after the last dose, sometimes up to 24 hours after heavy use. In urine, metabolites are detectable for 2–4 days.
Will a standard urine drug screen find ketamine?
Most standard "5-panel" or "10-panel" urine immunoassays do not test for ketamine. A specific ketamine assay or a comprehensive drug screen (LC-MS) is needed. Tell the lab if ketamine is suspected.
Why is this ordered in emergency rooms?
When a young adult presents with dissociation, nystagmus, hallucinations, raised blood pressure and heart rate, especially after a club or festival, ketamine is a leading differential. A blood level confirms it and rules out other causes of altered mental status.
Can ketamine be used legally?
Yes — ketamine is on the Indian schedule for hospital and anaesthetic use. It is also used off-label by psychiatrists for treatment-resistant depression. Possession or use outside a medical context is illegal in India.
Is the test used for suspected drug-facilitated assault?
Yes, with strict chain-of-custody. Because ketamine clears blood quickly, a sample within 12 hours is critical. Urine samples extend the window to 2–4 days. Tell the treating doctor or police if assault is suspected so the correct protocol is followed.
What about long-term ketamine effects?
Chronic use is associated with "ketamine bladder" (severe cystitis with frequency, urgency, and pain), cognitive impairment, and dependence. Anyone testing positive repeatedly should be referred for addiction-medicine support.
Related Drugs / Therapeutic Monitoring tests
Tests commonly ordered alongside KETAMINE, or that help interpret an unexpected result.
Sources & references
- NCBI StatPearls — Ketamine Toxicity · accessed 2026-05-30T00:00:00.000Z
- NIH NIDA — Club Drugs (Ketamine) · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Drug Screen, Comprehensive · accessed 2026-05-30T00:00:00.000Z
- FDA — Ketalar (Ketamine) Prescribing Information · accessed 2026-05-30T00:00:00.000Z
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