Ketamine does not typically keep you awake. In fact, research on people receiving therapeutic ketamine infusions shows the opposite: total sleep time increases on the nights following treatment, and time spent awake during the night decreases. That said, a small percentage of people do experience insomnia as a side effect, and the drug’s effects on brain chemistry are complex enough that individual responses vary.
The confusion is understandable. Ketamine triggers a surge of glutamate, the brain’s primary excitatory chemical, which temporarily increases cortical arousal. But this acute stimulation during and shortly after a dose doesn’t translate into lasting wakefulness for most people. Here’s what the evidence actually shows about ketamine and sleep.
What Ketamine Does to Your Brain Chemistry
Ketamine blocks a specific receptor involved in how brain cells communicate with each other. When that receptor is blocked, something counterintuitive happens: the brain releases a flood of glutamate, its main “go” signal. This burst of excitatory activity increases what researchers call cortical excitability, measurable as gamma wave activity on brain scans. During and immediately after ketamine administration, your brain is genuinely more activated than usual.
This glutamate surge also activates wake-promoting neurons in the hypothalamus, the same neurons that become hyperactive during sleep deprivation and whose absence causes narcolepsy. So at the molecular level, ketamine does engage the brain’s arousal systems. The key question is how long this lasts and whether it actually disrupts your ability to sleep.
How Sleep Changes After a Ketamine Session
A study of 30 people with major depression found that on the night after a ketamine infusion, total sleep time significantly increased compared to baseline. The percentage of deep sleep (slow-wave sleep) rose from about 3.5% to 4.7%, and the time it took to enter REM sleep dropped from roughly 79 minutes to 61 minutes. Time spent awake during the night also decreased. These changes indicate more consolidated, higher-quality sleep, not less of it.
These improvements persisted into the second night after treatment as well, suggesting the effect isn’t just a rebound from acute stimulation. A separate study tracking patients through eight ketamine infusions found no significant changes in self-reported insomnia, nighttime restlessness, early morning waking, or oversleeping at seven-day follow-up compared to baseline. In other words, the treatment course didn’t meaningfully disrupt sleep patterns in either direction for most participants.
The Insomnia Exception
Despite the overall trend toward better sleep, insomnia does appear on the side effect list. In clinical trials of esketamine (the nasal spray form approved for treatment-resistant depression), about 8% of patients reported insomnia, compared to 7% on placebo. That’s a real but small difference, suggesting that for a minority of people, ketamine-related brain stimulation does interfere with sleep.
The FDA labeling for esketamine also lists insomnia among symptoms that can occur with misuse or abuse of the drug, alongside anxiety, disorientation, and hallucinations. This points to a dose-dependent relationship: at higher or more frequent doses, or when the drug is used outside clinical settings, sleep disruption becomes more likely.
Dose Makes the Difference
Ketamine’s effects shift dramatically depending on how much you take. At sub-anesthetic doses (the range used for depression treatment, typically 0.1 to 0.5 mg/kg intravenously), the drug produces a dissociative, mildly stimulating experience that wears off within a couple of hours. At higher doses, it acts primarily as a sedative, suppressing consciousness rather than enhancing alertness.
The speed of administration matters too. Rapid dosing or combining ketamine with other sedatives can produce exaggerated responses and prolonged recovery times. Patients receiving ketamine in any form are advised not to drive or operate machinery for up to 24 hours afterward, partly because of lingering effects on alertness and coordination, though this reflects impairment rather than stimulation.
Ketamine and Your Internal Clock
One of the more surprising findings is that ketamine appears to directly affect your body’s circadian machinery. Animal research has shown that ketamine downregulates several core clock genes in the brain, including Per2 and Dbp, which help govern your sleep-wake cycle. Remarkably, these are the same gene expression changes seen after sleep deprivation.
This overlap between ketamine and sleep deprivation at the molecular level is significant because both produce rapid antidepressant effects. Researchers have found 64 common gene transcripts altered by both ketamine and sleep deprivation, concentrated in brain regions rather than peripheral organs. The implication is that ketamine may partly work by resetting circadian signaling, temporarily mimicking the neurochemical state of extended wakefulness even while the person is able to sleep normally.
This helps explain the paradox: ketamine engages arousal-related pathways and alters clock genes associated with wakefulness, yet most people sleep better, not worse, after receiving it. The drug appears to activate restorative processes linked to sleep pressure (the biological drive to sleep that builds the longer you stay awake) without requiring you to actually stay awake.
What to Expect in Practice
If you’re receiving ketamine for depression or another condition, the acute effects of a standard infusion typically last 45 minutes to a couple of hours. During this window you may feel alert, dissociated, or mildly stimulated. Once the immediate effects subside, most people do not have trouble falling asleep that night. Many sleep more deeply than usual.
If you’re using ketamine recreationally or at higher doses, the picture changes. Higher doses are more sedating in the short term but can lead to more unpredictable aftereffects, including difficulty sleeping. Combining ketamine with stimulants or other substances further complicates the response. The 8% insomnia rate from clinical trials likely underestimates what happens with uncontrolled use, though precise data on recreational users and sleep is limited.
For the small number of people who do experience post-ketamine insomnia, the timing of treatment may help. Receiving infusions earlier in the day gives the acute glutamate surge more time to resolve before bedtime, though this hasn’t been formally studied as a countermeasure.