A single ketamine infusion session typically takes about 40 minutes, with an additional monitoring period afterward that brings your total time in the clinic to roughly 2 hours. But “how long does it last” has several layers: the session itself, how long the drug stays in your system, how long symptom relief holds, and how long the overall treatment course runs. Each of these timelines is different.
How Long a Single Session Takes
For IV ketamine, the standard protocol is a slow drip infused over 40 minutes at a low dose. You’ll be seated or reclined in a clinic setting, often with dimmed lighting and minimal stimulation. Some people feel dissociative or floaty effects during the infusion, which begin to fade shortly after the drip stops. The drug itself has a half-life of roughly 2.5 to 3 hours, meaning most of it clears your system within a few hours.
For esketamine nasal spray (the FDA-approved brand name is Spravato), the administration itself is quicker, but the required monitoring period is longer. Federal labeling mandates that patients be observed for at least 2 hours after each session before a clinician determines they’re stable enough to leave. You can’t drive yourself home afterward with either format.
Sublingual ketamine lozenges (troches) are sometimes prescribed for at-home use under a provider’s guidance. These have lower bioavailability, around 17 to 29 percent when held under the tongue, and their effects come on more gradually. The terminal half-life for sublingual ketamine is about 3 hours.
How Quickly Relief Begins
Ketamine’s reputation as a fast-acting treatment for depression is well earned. In clinical studies of treatment-resistant major depression, patients showed a large measurable drop in depression scores within 2 hours of their first infusion. One study reported a 71 percent response rate at 24 hours. That speed is remarkable compared to traditional antidepressants, which commonly take 4 to 6 weeks to show meaningful improvement.
Not everyone responds this quickly, and some people don’t respond at all. But for those who do, the shift can feel dramatic within the first day or two.
How Long the Effects Last After One Treatment
This is where expectations need adjusting. A single ketamine infusion provides relief that is real but temporary. Most people who respond to one session experience a relapse of symptoms within several days to about one week. There’s variability from person to person, but the general pattern is clear: one infusion is not a lasting fix.
That’s why ketamine is rarely given as a one-time treatment. The therapeutic model relies on a series of sessions to build a cumulative effect.
The Standard Induction Series
Most IV ketamine clinics use an induction protocol of six infusions spread over two to three weeks. The Cleveland Clinic’s chronic pain protocol, for example, uses five consecutive daily infusions. Depression protocols more commonly space sessions two to three days apart over a two-week window.
The goal of this concentrated initial series is to stack the effects. While a single session might hold for a week, the cumulative benefit of a full induction series can last months for some patients without further treatment. The relief builds with each session, and by the end of the series, many people report a more sustained improvement than any single infusion could provide.
That said, “months” is the optimistic end of the range. Most patients will eventually need additional sessions to maintain their gains.
Maintenance Treatments and Long-Term Schedules
After the initial induction series, most patients transition to a maintenance schedule. The interval varies widely based on individual response. Some people come in for booster sessions every 3 to 4 weeks. Others stretch to every 6 or 8 weeks. The typical maintenance window falls somewhere in the 2 to 8 week range between sessions.
Some clinics schedule regular monthly boosters of one or two sessions. Others take a more reactive approach, where patients schedule additional infusions when they notice symptoms returning. A booster round might involve anywhere from 2 to 6 infusions depending on how much ground has been lost.
For sublingual ketamine prescribed at home, treatment durations tend to be longer and more ongoing. In one study tracking patients using ketamine lozenges for chronic pain, the average duration of treatment was over 31 months, with more than half of patients still using them at the time of the study. This suggests that for many people, ketamine becomes a long-term management tool rather than a short course with a defined endpoint.
What Affects How Long Relief Lasts
Several factors influence how durable your response will be. The condition being treated matters: people using ketamine for depression sometimes respond differently than those using it for chronic pain or PTSD. Your individual brain chemistry plays a role that no provider can fully predict in advance.
Concurrent therapy also makes a difference. Many providers recommend pairing ketamine treatments with psychotherapy, using the window of improved mood and cognitive flexibility that ketamine opens to do deeper therapeutic work. Patients who combine ketamine with active psychological treatment often report longer-lasting benefits than those relying on ketamine alone.
Lifestyle factors like sleep, exercise, and stress levels can accelerate or slow the return of symptoms between sessions. And for depression specifically, the severity and treatment resistance of the condition before starting ketamine tends to correlate with how frequently maintenance sessions are needed.
Planning Your Time Commitment
For the induction phase, expect to block out about 2 hours per session, two to three times a week, for two to three weeks. That’s a significant time investment, especially since you’ll need someone to drive you to and from each appointment.
Once you move to maintenance, the commitment drops considerably. One or two sessions every few weeks, each lasting about 2 hours at the clinic, is the typical ongoing pattern. Some people gradually extend the intervals between sessions over time, while others settle into a steady rhythm that holds for years.