Ketamine Side Effects: Short-Term Effects and Long-Term Risks

Ketamine is generally well tolerated at the doses used in clinical settings, but it is not side-effect-free. This guide separates the common, short-term effects you should expect during and right after a session from a less common, long-term risk tied to frequent or high-dose use. For the full picture on how ketamine therapy works, start with our ketamine therapy guide.

Short-term side effects

These effects show up during dosing or in the observation window right after, and typically resolve within one to two hours. They are documented across Spravato (esketamine) clinical trials and the IV ketamine research literature.

• Dissociation. A sense of detachment from your body, surroundings, or sense of time. This is the expected drug effect, not a side effect in the strict sense, but it can feel disorienting the first time.
• Nausea. One of the most commonly reported effects. Clinics often have anti-nausea medication on hand.
• Rise in blood pressure and heart rate. Ketamine is a stimulant to the cardiovascular system during dosing. This is why vital signs are checked before, during, and after in a monitored setting.
• Dizziness and unsteady balance. Another reason sessions require a monitored setting and why you cannot drive yourself home afterward.
• Blurred vision or double vision. Usually brief and resolves as the drug wears off.
• Drowsiness or grogginess in the hours after dosing.
• Anxiety or a sense of unease during the dissociative window, more common in first sessions.

Most people feel back to baseline within one to two hours, though esketamine (Spravato) labeling asks patients to remain until they are cleared by clinic staff, generally around two hours after dosing.

What monitoring looks like during a session

Because of the effects above, ketamine is not something you take and then immediately drive away from. In a clinic, staff check blood pressure and heart rate before dosing, watch you through the dissociative window, and check again before you leave. At-home telehealth models still require a sober monitor present and a plan for what to do if something feels wrong. Our what to expect at your first ketamine-assisted therapy session guide walks through the full visit from screening call to discharge.

Long-term risk: ketamine-induced cystitis

Separate from the short-term effects above, urology literature has documented a bladder and urinary-tract condition associated with frequent, high-dose ketamine use, generally called ketamine-induced cystitis or ketamine-associated lower urinary tract symptoms. This pattern shows up in case reports and reviews of heavy, repeated use — most of that literature comes from recreational, high-frequency dosing, with some reports also describing symptoms in patients using ketamine clinically over extended periods.

Reported symptoms include:

• Bladder or pelvic pain
• Urinary urgency — a sudden, strong need to urinate
• Urinary frequency — needing to go much more often than usual
• Hematuria — blood in the urine
• In more advanced case reports, a reduced bladder capacity that can require specialist care

This is a real, described risk, not a fabricated one — but it is also not a reason to panic about a single supervised medical dose. The case reports and reviews describing it center on frequent, high-dose, often unsupervised use over months or years. The risk is understood to be dose- and frequency-dependent: the more often and the higher the dose, the more it has been reported. This is exactly the kind of pattern that a prescriber monitoring your treatment over time is positioned to catch early.

Other risks tied to frequent use

Ketamine also carries a recognized potential for misuse with frequent, unsupervised, escalating use, which is one reason it remains a Schedule III controlled substance and why legitimate treatment happens under a prescriber's supervision rather than as a self-directed routine. Cognitive effects such as difficulty concentrating or memory complaints have also been reported with heavy long-term use, separate from the brief disorientation felt during a session.

When to call your prescriber — or 911

Most side effects resolve on their own within the observation window. Contact your prescriber promptly if you notice new or worsening urinary symptoms, mood changes that persist between sessions, or escalating anxiety around dosing. Call 911 for chest pain, one-sided weakness, slurred speech, a severe headache unlike any before, or unresponsive breathing.

How clinics manage these risks

Reputable ketamine programs manage these risks with a few standard practices:

• Screening before treatment for cardiovascular history, prior substance-use history, and baseline blood pressure.
• Monitored dosing with vital-sign checks, so the short-term effects above are caught and managed in real time.
• A set course and taper rather than open-ended, self-directed dosing, which limits cumulative exposure.
• Periodic check-ins where urinary symptoms and mood are asked about directly, so early bladder or mood changes are not missed.

See our ketamine therapy guide for how the three access models — in-clinic IV, Spravato, and at-home telehealth — differ on supervision, or use our find a ketamine provider tool to locate a screened clinic.