Ketamine therapy side effects: what to know before you decide
Written by Abdo Mostafa, MD (medical degree earned in Egypt). Clinically reviewed by Erik Lee, PMHNP-BC. Published September 19, 2026. Last reviewed September 19, 2026.
If depression hasn’t budged after several medications, ketamine has probably come up, along with a lot of ads for it. This is for anyone weighing it and wondering what the side effects look like in real life.
The short answer: the most common ketamine therapy side effects are dissociation (feeling detached or dreamlike), a temporary rise in blood pressure, nausea, dizziness, and sleepiness. They tend to show up within minutes of a dose and fade over a few hours. The rarer problems, such as bladder irritation, misuse, or a bad reaction with nobody nearby, are tied mostly to frequent dosing and thin monitoring. That makes the setting worth as much attention as the drug.
The basics
Ketamine works differently from standard antidepressants. It blocks NMDA receptors in the brain’s glutamate system, and some people notice a mood shift within hours to days. Most antidepressants take weeks.
One form is FDA approved for depression. Esketamine (Spravato) is a nasal spray given in certified clinics for treatment-resistant depression. IV infusions, lozenges, and compounded nasal sprays are off-label, and compounded ketamine has not been reviewed by the FDA for safety, effectiveness, or quality (FDA, 2023).
Most side effects are short. With esketamine, blood pressure increases peak about 40 minutes after a dose and last around four hours. That window is why clinics keep you for at least two hours.
It is a controlled substance. Ketamine is Schedule III. The potential for misuse is real, and it belongs in any honest screening conversation.
What are the most common ketamine therapy side effects?
Three effects account for most of what people feel on a dosing day.
Dissociation. Time can feel stretched, the room may look unfamiliar, or your body may feel far away. Most people in the esketamine trials had some degree of it. It can be strange without being dangerous, and it usually settles while you are still being monitored. Ketamine can potentially worsen psychosis, so a history of psychosis or frequent dissociation is something to raise before the first dose. What helps: knowing it is coming, a quiet room, and a clinician close by.
Blood pressure and heart rate. Both can climb for a few hours. The label calls for a blood pressure check before and after each dose, and esketamine is contraindicated for people with aneurysmal vascular disease or a history of bleeding in the brain. If you take a stimulant for ADHD, say so. What helps: bring your full medication list and any recent home readings to the evaluation.
Nausea, dizziness, and sleepiness. Clinics often ask you to skip food for two hours beforehand. You will need a ride home, and driving waits until the next day, after a full night of sleep. Alcohol, benzodiazepines, and opioids can potentially deepen the sedation, so your prescriber needs to know about them. Slowed breathing is rare at these doses, and it is the reason the esketamine label calls for oxygen monitoring during those two hours.
Longer-term questions
Bladder symptoms. Ulcerative and interstitial cystitis have been reported with long-term off-label use and misuse of ketamine. Pain, urgency, or blood in the urine is worth reporting early.
Misuse and dependence. A systematic review of 16 studies found few cases of tolerance or dependence during depression treatment, and the authors still stressed supervised dosing and close monitoring. A history of substance use calls for a careful conversation with your prescriber before starting.
Thinking and memory. Memory problems have been reported with repeated ketamine misuse. In esketamine trials lasting one to three years, cognitive testing stayed stable. Data on off-label ketamine over the long run is thinner.
Is at-home ketamine therapy safe?
It depends on how much screening and monitoring comes with it. Many telehealth platforms now mail compounded lozenges after a short video visit. The FDA warned in 2023 that using compounded ketamine without a health care provider monitoring for sedation, dissociation, and blood pressure changes may put patients at risk for serious adverse events.
Comparison: supervised clinical setting vs unsupervised at-home dosing
| Supervised clinical setting | Unsupervised at-home dosing | |
|---|---|---|
| Product | Spravato, or IV or IM ketamine | Usually compounded lozenges or spray |
| Screening | Typically a full psychiatric and medical history | Often one brief video visit |
| Blood pressure | Checked before and after the dose | Often not checked |
| During the dose | Staff on site for about two hours | You, or whoever is home |
| If something goes wrong | A clinician responds in the room | A phone call, or 911 |
Some at-home programs do build in real screening, a blood pressure cuff, a sober adult in the room, and a clinician on call. Ask before you assume either way.
Red flags
Pause and call your prescriber the same day if you have:
Pain or burning when you urinate, blood in your urine, or a sudden need to go far more often
Confusion, unusual thoughts, or a detached feeling that lasts into the next day
Cravings, or taking doses more often or in larger amounts than prescribed
Depression that is getting worse, or new thoughts of suicide
Call 911 for chest pain, a sudden severe headache, trouble breathing, or anyone who cannot be woken after a dose.
Practical tips
Ask which product you would get (Spravato, IV, or a compounded lozenge or spray) and whether it is FDA approved for depression.
Ask who checks your blood pressure, and who is physically with you during the dose and for two hours after.
Bring a full medication list, including stimulants, benzodiazepines, and sleep medications.
Share any history of substance use, psychosis, heart disease, aneurysm, or stroke.
Arrange a ride and keep the rest of the day clear.
Keep your therapist and regular prescriber informed. Ketamine is one part of a plan, and the people managing the rest of it need to know.
The bottom line
Ketamine therapy side effects are mostly short-lived and manageable when someone qualified screens you beforehand and watches during the dose. Risk climbs when dosing is frequent, the product is compounded, and no one is in the room. Ketamine can help some people with treatment-resistant depression. It won’t suit everyone, and a careful evaluation is how you find out which group you are in.
Want guidance tailored to you?
A psychiatric evaluation is a good first step if you are weighing ketamine. At Celium Healthcare, Erik Lee, PMHNP-BC, sees adults across Oregon by telehealth, reviews what you have already tried, and can refer you to a vetted clinic when ketamine makes sense. Check accepted insurance plans, then schedule a visit.