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The most common side effects of ketamine therapy are dissociation, nausea, dizziness, temporary changes in blood pressure and heart rate, and drowsiness. Most patients want to know what are the side effects of ketamine therapy before their first session, and the reassuring answer is that nearly all of them are short-lived, predictable, and resolve within one to two hours of treatment. Ketamine is a dissociative anesthetic, meaning it temporarily changes how the mind processes sensory input, which is also part of what produces the floating or detached feeling many patients describe. Below is a breakdown of which side effects are common, which are rare, and when a symptom warrants a call to your provider rather than just some rest. Reviewing a first appointment checklist ahead of time can help you know what to expect.
Quick Answer
The most common side effects of ketamine therapy are dissociation, mild nausea, dizziness, a temporary rise in blood pressure or heart rate, and drowsiness. These typically begin within minutes of dosing and resolve within 1 to 2 hours. Rare but more serious effects, such as a significant blood pressure spike, panic during a session, or an allergic reaction, are uncommon at therapeutic doses and are managed through pre-treatment screening and monitoring during the session.
Common Side Effects
These effects are experienced by a large share of patients and are considered a normal part of ketamine treatment.
Dissociation
Nearly universal at therapeutic doses. Patients describe a sense of detachment from the body, floating, or a dreamlike distortion of time. Vision may blur, colors can seem more vivid, and depth perception often shifts as well. It begins within minutes and typically resolves within 1-2 hours. Many providers consider dissociation part of how the treatment works rather than a problem to correct.
Nausea
According to MedlinePlus, nausea and vomiting are among the most frequently reported reactions to ketamine, affecting an estimated 10 to 30 percent of patients. It usually peaks during the session and clears within 1-2 hours. Fasting for 4-6 hours beforehand, an anti-nausea medication such as ondansetron, or ginger can lower the risk.
Dizziness, Blood Pressure, and Heart Rate
Lightheadedness, a temporary rise in blood pressure, and a faster heartbeat are all common and usually mild. Clinics monitor vital signs during in-clinic sessions for this reason, and patients doing at-home sublingual treatment are often asked to check blood pressure before and after dosing. Move slowly when sitting up, and tell your provider if you have a history of hypertension.
Drowsiness and Emotional Sensitivity
Fatigue, mental fog, and feeling emotionally raw or tearful are common after a session and can last several hours. Plan to rest for the remainder of the day; see our guide on what to do after treatment. Processing unexpected emotions through journaling or integration therapy is a normal and often useful part of the process.
Less Common Side Effects
These occur less often but are still within the expected range for ketamine treatment.
- Headache: Mild to moderate, usually responds to over-the-counter pain relief and hydration.
- Vivid dreams: Unusually memorable dreams the night after treatment, typically limited to the first night or two.
- Slurred or difficult speech: More likely at higher doses; resolves completely once the session ends.
- Urinary frequency: Uncommon at therapeutic doses. The bladder effects associated with ketamine are mainly linked to chronic, heavy recreational use rather than supervised clinical dosing, though persistent changes should be reported to your provider.
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Compare treatment optionsRare but Serious Side Effects
A small number of patients experience a significant spike in blood pressure that requires medical attention, severe anxiety or panic during a session, a true allergic reaction (hives, swelling, or difficulty breathing), or laryngospasm, an involuntary spasm of the vocal cords that is a known risk mainly at higher anesthetic doses. According to Mayo Clinic, thorough pre-treatment screening and clinical monitoring are the main safeguards against these rare complications, which is why disclosing your full medical history matters before starting treatment.
When to Contact Your Provider
Reach out to your provider if you notice any of the following after a session. You are never wrong to raise a concern, even a minor one; see our guide on questions to ask your ketamine provider for more on staying in touch between sessions.
Contact Your Provider If You Notice
- Side effects that do not resolve within a few hours after the session
- Persistent nausea or vomiting
- Severe or prolonged headache
- Blood pressure that stays elevated well after treatment
- Confusion or disorientation lasting more than a few hours
- Mood worsening between sessions
- Any new or unusual symptom, or anything that concerns you
Key Takeaway
Side effects tend to become milder and more predictable with each session as your body adjusts to ketamine. Weigh the temporary discomfort against the potential benefit: for many patients who have not found relief through other treatments, manageable side effects are a reasonable trade-off for improvement in depression, anxiety, or chronic pain. According to the National Institute of Mental Health, standard depression treatments do not work for everyone, which is part of why patients and providers weigh options like ketamine against their individual risks and benefits.
Helpful next step
See our full safety overview for contraindications, screening requirements, and how clinics monitor patients during treatment.
Learn More
If you have questions about how ketamine side effects might apply to your health history, our team can help you find next steps.
Frequently Asked Questions
No. Most patients report that side effects become milder and more predictable as they become familiar with the experience and their body adjusts to the medication.
No. Dissociation and drowsiness typically persist for 1-2 hours after a session, so you will need someone to drive you or arrange other transportation.
No. Nausea affects an estimated 10 to 30 percent of patients and is usually managed with fasting beforehand, anti-nausea medication, or ginger. Tell your provider if it becomes severe or persistent.
Most common side effects, including dissociation, dizziness, and elevated blood pressure, resolve within 1 to 2 hours of the session ending. Drowsiness and emotional sensitivity can occasionally last into the next day.
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