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This is the complete beginner's guide to ketamine therapy: what ketamine is, how it works in the brain, who typically qualifies for treatment, and what to expect from a first session through ongoing care. Ketamine therapy uses low, controlled doses of ketamine, a medication used safely in medicine for more than 50 years, to treat conditions such as depression, anxiety, post-traumatic stress disorder (PTSD), and chronic pain. Unlike traditional antidepressants that can take weeks to produce results, ketamine often brings noticeable improvement within hours or days of the first session.
Quick Answer
Ketamine therapy uses low, controlled doses of ketamine, delivered by IV infusion, intramuscular injection, sublingual lozenge, or the FDA-approved nasal spray Spravato, to treat treatment-resistant depression, PTSD, anxiety, and certain chronic pain conditions. Most patients complete an initial series of sessions over a few weeks under medical supervision, and many report improvement within hours or days rather than the weeks typical of standard antidepressants. A typical path starts with a screening consultation, continues through an initial series of sessions, and moves into maintenance treatment scheduled around how long benefits last for each patient.
What Is Ketamine Therapy?
Ketamine was originally developed as a surgical anesthetic. In the early 2000s, researchers found that much smaller, sub-anesthetic doses produced rapid antidepressant effects, a discovery that reshaped depression research. Since then, a growing body of clinical research has supported ketamine's use for treatment-resistant depression, suicidal ideation, and several other mental health conditions, according to the National Institute of Mental Health (NIMH).
How Does Ketamine Work?
Ketamine works differently from traditional antidepressants like SSRIs or SNRIs, which primarily target serotonin or norepinephrine. Ketamine instead acts on glutamate, the brain's most abundant excitatory neurotransmitter, which helps neurons communicate with one another. It blocks NMDA receptors, a type of glutamate receptor, triggering a cascade of neurological changes that promote neuroplasticity, the brain's ability to form new neural connections. This is why many researchers describe ketamine as working through a fundamentally different mechanism than conventional psychiatric medications, according to MedlinePlus, the National Library of Medicine's consumer drug information resource.
Ketamine also appears to raise levels of brain-derived neurotrophic factor (BDNF), a protein that supports the growth and survival of neurons. This may help explain why the benefits of ketamine therapy can last well beyond the time the medication remains active in the body.
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Compare treatment optionsWho Can Benefit From Ketamine Therapy?
Ketamine therapy has shown promise for a range of conditions, including:
- Treatment-resistant depression, meaning depression that has not responded adequately to two or more traditional antidepressants
- Major depressive disorder, particularly when rapid relief is needed
- Suicidal ideation, where ketamine can reduce suicidal thoughts within hours
- Anxiety disorders, including generalized anxiety and social anxiety
- Post-traumatic stress disorder (PTSD), where it may help patients process and reduce the intensity of traumatic memories
- Obsessive-compulsive disorder (OCD), where emerging research shows benefits for some patients
- Chronic pain conditions, including fibromyalgia, complex regional pain syndrome, and neuropathic pain
Ketamine therapy is often considered after other treatments have not provided sufficient relief, though it is increasingly explored earlier in treatment as well. Veterans managing service-related PTSD are one group where earlier access has become more common.
Routes of Administration
Ketamine therapy is available through several routes, each with different onset times, settings, and levels of medical supervision.
Intravenous (IV) Infusion
IV infusion is the most researched and clinically established method. Ketamine is delivered directly into the bloodstream through an IV line over about 40 minutes, allowing for precise dosing and fast absorption. IV infusions are always administered in a clinical setting under medical supervision. See our guide on how long a ketamine session lasts for a full session timeline.
Intramuscular (IM) Injection
IM injection delivers a single dose into the muscle, typically in the upper arm or thigh. Onset is slightly slower than IV but faster than oral routes, and IM injections are also given in clinical settings.
Sublingual (Under the Tongue)
Sublingual lozenges or troches dissolve under the tongue. This route has lower bioavailability than IV or IM, meaning a smaller percentage of the medication reaches the bloodstream. Sublingual ketamine is sometimes prescribed for at-home use under a provider's supervision. Learn how this compares to other oral formulations in our oral vs. sublingual ketamine guide.
Nasal Spray (Spravato)
Esketamine, sold under the brand name Spravato, is an FDA-approved nasal spray for treatment-resistant depression. It is a close molecular relative of ketamine and is administered only in certified healthcare settings. Spravato is currently the only FDA-approved form of ketamine for psychiatric use. See our full ketamine vs. esketamine comparison for differences in efficacy, cost, and access.
What to Expect at Your First Session
Most providers begin with a screening consultation to review your medical history, current medications, and treatment goals before scheduling your first session. During an IV or IM appointment, a nurse or provider monitors your heart rate, blood pressure, and oxygen levels throughout the session. Sessions typically run 40 minutes to an hour depending on the route of administration, plus recovery time before you are cleared to leave. Because ketamine causes temporary dissociation, you will need someone to drive you home afterward. See our guide on how long a ketamine session lasts for a full session timeline, and review our tips for preparing for treatment so you know what to bring and how to plan your day.
Safety and Side Effects
Ketamine therapy is generally administered under medical supervision because it can cause temporary dissociation, elevated blood pressure, nausea, or dizziness during a session, according to MedlinePlus. These effects typically resolve within a couple of hours as the medication clears the body. Providers screen patients for conditions such as uncontrolled high blood pressure, certain heart conditions, and a history of psychosis, since these may affect whether ketamine therapy is appropriate. For a full breakdown of what to expect and how providers manage risk, see our ketamine safety and side effects guide.
Advantages
- Can bring noticeable relief within hours or days rather than the weeks typical of standard antidepressants
- Works through a different mechanism than SSRIs or SNRIs, offering an option when other treatments have not worked
- Available through multiple routes, including IV, IM, sublingual, and the FDA-approved nasal spray Spravato
Considerations
- Most routes are used off-label, so insurance coverage and out-of-pocket cost can vary widely between patients
- Requires medical supervision, especially for IV and IM administration, due to temporary dissociation and blood pressure changes
- Benefits can fade over time, meaning many patients need ongoing maintenance sessions
Getting Started: Action Checklist
- Schedule a screening consultation to review your medical history, current medications, and treatment goals
- Ask your provider about their protocol, including route of administration and session frequency
- Arrange a ride home, since dissociative effects mean you should not drive after a session
- Review a preparing for treatment guide before your appointment so you know what to expect
- Plan for follow-up care and maintenance sessions if you respond well to initial treatment
Key Takeaway
Ketamine therapy is rarely a one-time treatment. Most patients complete an initial series of sessions, then follow up with periodic maintenance treatment to sustain the benefits over time.
References
- NIMH: Depression Overview, National Institute of Mental Health information on depression symptoms, causes, and treatments
- Mayo Clinic: Depression Diagnosis and Treatment, including information on treatment-resistant depression and ketamine-based approaches
- NIMH Science News, featuring ongoing research into ketamine as a depression treatment
- MedlinePlus: Ketamine Injection, National Library of Medicine drug information on ketamine, including uses and safety
- WHO: Depressive Disorder Fact Sheet, World Health Organization overview of depression as a global health concern
Helpful next step
See how ketamine therapy compares to talk therapy alone before deciding on a treatment path.
Learn More
Have questions about starting ketamine therapy or finding a provider near you?
Frequently Asked Questions
Esketamine, sold as Spravato, is the only ketamine-based treatment approved by the FDA for psychiatric use, specifically treatment-resistant depression. IV, IM, and sublingual ketamine are used off-label for mental health conditions, meaning providers prescribe an FDA-approved drug for a use not specifically listed on its label, a common and legal practice in medicine. See our ketamine vs. esketamine comparison for more on how the two differ.
Effects from a single session can last from several days to a couple of weeks, though this varies by individual and condition. Many providers schedule an initial series of sessions over two to three weeks, then move to periodic maintenance treatment to extend benefits. Our maintenance treatment guide covers how providers adjust dosing and frequency over time.
Some patients find that benefits fade over time or that their body adjusts to the treatment. If this happens, a provider may adjust the dose, route of administration, or session frequency. Read more in our guide on what happens when ketamine stops working.
Coverage varies by insurer, diagnosis, and route of administration. Spravato is more likely to have insurance coverage since it carries FDA approval for treatment-resistant depression, while IV, IM, and sublingual ketamine are typically billed as out-of-pocket or self-pay treatments because they are used off-label. Confirm coverage details directly with your insurance provider and treatment clinic before starting care.
Some medications can interact with ketamine or affect how well it works, so providers review your full medication list during screening. See our guide on ketamine and other medications for details on common interactions to discuss with your provider.
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