Ketamine Therapy Side Effects
Mild, Manageable, and Gone in Hours
This page walks you through the most common ketamine side effects—when they happen, how long they last, what’s normal, and what’s rare—based on real treatment protocols and patient experience.
Frequently Asked Questions About Ketamine Side Effects
1. What are ketamine’s side effects—and when do they actually happen?
In the first few minutes, before ketamine crosses the blood-brain barrier and dissociation begins some people may experience nausea or dizziness—especially with slower-absorbing methods like oral lozenges or the esketamine Spravato nasal spray. About 7% of patients report nausea or vomiting, but this can be prevented by taking anti-nausea medication before the session or refraining from drinking or eating in the hours leading up to it.
Once ketamine crosses into the brain and the “journey” begins, most ordinary sensory input fades because you enter an alternate state of consciousness. Even the minority of patients who do experience side effects during this stage stop feeling them. Dissociation interrupts the brain’s ability to process external signals like discomfort, nausea, or pain—not by removing the cause, but by changing what the mind can perceive.
After the journey ends—when awareness returns—almost all patients experience grogginess, imbalance, mental fog, and fatigue for a few hours. Some may experience nausea. These effects are most pronounced during the comedown phase, as the drug’s dissociative effects begin to wear off and your brain shifts back into normal consciousness. For many, it feels like waking up from a long nap in a dim room—slow, heavy, a little unsteady, but not unpleasant. The fog usually fades by evening.
Route of administration matters. IV ketamine kicks in quickly, leaving less time for early side effects to surface. Oral and nasal methods absorb more slowly, which may increase the chance of pre-journey symptoms.
Understanding ketamine side effects means understanding when they happen—not just what they are.
2. Do the side effects of ketamine therapy go away quickly—or do they linger?
Almost all the side effects– grogginess, imbalance, fatigue, nausea or brain fog–fade away over the course of 4 to 6 hours. Think of it like sliding down a long, gentle ramp—not crashing, just slowly returning to baseline.
Unlike SSRIs, which can produce daily side effects that accumulate over weeks, ketamine’s side effects are temporary and usually resolve within a few hours. There’s no long adjustment period, and no waiting weeks to find out how your body will respond. What you feel, you feel that day—and then it’s over.
3. Are there any serious side effects I should know about—or do those mostly come from recreational use?
Yes, serious but rare side effects exist—but almost all come from much higher, more frequent doses than you’d ever get in depression treatment. In clinical settings, the risk profile is low and well understood.
One example is bladder irritation, sometimes seen in people who use ketamine heavily as a party drug. At therapeutic doses, it’s extremely rare—and usually resolves if treatment is paused. Another rare side effect is a temporary rise in liver enzymes, which doesn’t usually cause symptoms and is often only spotted in routine labs.
The most serious side effects—things like long-term cognitive changes or prolonged psychotic symptoms—almost always involve misuse. The kind of misuse that happens outside of a clinic, not inside one. If you’re working with a licensed provider who screens for risks and adjusts the dose carefully, you’re not in that category.
4. Is dissociation a side effect of ketamine therapy—or is it part of how the treatment works?
Dissociation isn’t a side effect. It’s the mechanism of action.
Medical websites often call it a side effect because they rely on outdated pharmaceutical templates—where anything strange or unfamiliar gets lumped in with symptoms like nausea or dizziness.
But dissociation isn’t a secondary physiological response. It’s the brain’s direct response to ketamine entering key neural pathways. What you feel as dissociation is what’s happening in your brain—disruptions to the default mode network, increased neuroplasticity, and temporary decoupling of sensory input and self-awareness. That’s not a side effect. That’s the drug doing exactly what it’s supposed to do.
It can be disorienting. For some it’s uncomfortable; for others a fascination. But it’s not a bug in the system. It’s the system working.
How Can You Be Sure Ketamine Therapy Actually Works?
I pulled together 25+ systematic reviews from the last five years into one report—so you don’t have to rely on hype, guesses, or anecdotes. This is the highest level of real-world evidence we have.
Inside My Report You’ll Find
- What percent of patients enter remission—broken down by delivery method
- Which method is most effective—IV, injection, or Spravato nasal spray
- How fast ketamine can work to reduce or end symptoms
- Which combinations (like psychotherapy) may enhance response
- And a lot more…
Verified by the Platforms That Matter
This research summary report has been published across four trusted platforms that host peer-reviewed or open science content, including:
– Published ketamine research on Zenodo
– Ketamine evidence summary hosted on SSRN
– Scientific report on ketamine outcomes on Figshare
– Evidence-based ketamine therapy report on OSF
View the PDF Report Here:
From Queasy to Constipated
I definitely felt nauseous an hour or two after my first ketamine session. Luckily, my psychiatrist had given me a prescription for Zofran (ondansetron), but here’s the catch—it didn’t work all that well because I took it after I started feeling sick. Rookie mistake.
Once I learned to take it before the session, the nausea improved, but it didn’t disappear entirely. Eventually, I doubled the dose, and that did the trick—I never experienced nausea again. But then came the trade-off: Zofran put me squarely in the 9–11% of people who get constipated. So there I was, balancing it out with laxatives and, God help me, eating a lot of prunes.
I won’t lie—it was a hassle. But I seem to be in the minority here. Statistically and anecdotally, most people don’t need anti-nausea meds for ketamine therapy, and even if they do, they usually don’t deal with constipation. I’ve got a few friends who went through ketamine therapy, and none of them had the same issues I did.
When You Gotta Go You Gotta Go
During my first couple of ketamine sessions, I had such an urgent need to pee that it completely distracted me from the journey. I’d be mid-session, trying to stay present, and all I could think was, “I need to pee!”
The clinic mentioned that a few other people had experienced the same thing, but it wasn’t common. There’s not much you can do to eliminate it entirely, but I found a couple of tricks that helped: I stopped drinking water for a few hours before the session, and I always made sure to hit the bathroom right before the ketamine was administered.
These little adjustments made all the difference, letting me fully settle into the experience without distraction.
Rare Side Effects of Ketamine Therapy
I’ll admit, I had reservations about writing this section. Rare side effects are tricky to talk about because no matter how many times you say “rare,” people tend to latch onto them and think, If they’re mentioning it, it’s probably going to happen to me.
I get it—listing side effects can be scary. It’s like those drug commercials on TV where half the ad is a rapid-fire list of terrifying things that could happen, leaving you wondering why anyone would risk taking it. The truth is, those lists are there because the law demands it, not because the risks are common. The same goes for ketamine therapy.
Rare side effects are exceedingly uncommon, and in most cases, they happen when ketamine is misused—through illegal dosing or excessive use as a party drug. In a controlled clinical setting, with the low doses used to treat depression, these side effects are highly unlikely. But if you’re going to trust the process, it’s important to have all the facts. So, let’s talk about them.
Ketamine-induced cystitis, which can affect the bladder. Symptoms include urinary frequency, urgency, or discomfort, but here’s the thing: this condition is typically seen in people abusing ketamine at much higher doses than you’d ever get in a therapeutic setting. In the rare instances where bladder issues appear during treatment-resistant depression treatment, they usually resolve once the therapy is stopped.
Temporary elevation in liver enzymes. This one rarely causes symptoms and is often only noticed through routine blood tests. It’s something your care team might monitor if you’re undergoing long-term treatment, but for most people, it’s a non-issue.
There have also been very rare reports of prolonged psychological effects, like confusion, paranoia, or hallucinations, lasting beyond the treatment session. Again, these are incredibly rare and tend to resolve on their own or with slight adjustments to your treatment plan.
Finally, long-term or high-dose use of ketamine—like the kind seen in recreational settings—has been linked to cognitive changes, such as difficulty with memory or attention. But this is almost unheard of in therapeutic protocols, where doses are tightly controlled.
Pay These Rare Side Effects Little Mind
I know how easy it is to focus on the worst-case scenarios, but the reality is that these side effects are incredibly rare when ketamine is administered safely and professionally. The best analogy I can give is that these risks are like getting struck by lightning—not impossible, but highly unlikely, especially if you’re not standing in the middle of a storm.
Takeaway
In clinical ketamine therapy, rare side effects like cystitis or cognitive changes are almost always linked to misuse—outside medical settings, not inside them.