The most widely studied ketamine dose for depression is 0.5 mg/kg delivered intravenously over 40 minutes, and this remains the benchmark that most clinics and clinical trials use. But calling it a single “dose” oversimplifies things considerably. The amount of drug that reaches your brain depends on the route it takes into your body, your body composition, how often you receive it, and what other medications you’re on. Esketamine, the FDA-approved nasal spray version, uses its own fixed-dose schedule that looks nothing like an IV protocol. So while 0.5 mg/kg is the short answer, the practical reality of ketamine dosing involves a web of decisions that clinicians navigate on a patient-by-patient basis.
The 0.5 mg/kg Standard and What Happens Above and Below It
The 0.5 mg/kg IV dose emerged from early clinical trials as a sweet spot: strong enough to produce a meaningful antidepressant effect within hours, yet low enough to remain well below anesthetic levels. A placebo-controlled dose-ranging trial tested 0.1, 0.2, 0.5, and 1.0 mg/kg against an active placebo in people with treatment-resistant depression. The 0.5 mg/kg and 1.0 mg/kg doses both clearly outperformed placebo at day one, while the lowest dose (0.1 mg/kg) showed only a trend that didn’t hold up after adjusting for multiple comparisons. The higher 1.0 mg/kg dose didn’t produce meaningfully better depression outcomes than 0.5 mg/kg but did cause more dissociative symptoms and blood pressure spikes.1Molecular Psychiatry. Double-blind, placebo-controlled, dose-ranging trial of intravenous ketamine as adjunctive therapy in treatment-resistant depression (TRD)
A 2024 meta-analysis that pooled data across multiple studies found that doses above 0.5 mg/kg did not lead to greater treatment response than the standard dose.2PubMed. Efficacy of intravenous ketamine and intranasal esketamine with dose escalation for Major depression: A systematic review and meta-analysis That same analysis confirmed that some antidepressant response can be observed even at lower IV doses, though the evidence for doses at or below 0.2 mg/kg is less consistent. There is one trial, however, that complicates the picture: a study comparing 0.5 mg/kg and 0.75 mg/kg as bolus injections found the higher dose produced a response in roughly 80% of patients compared to about 48% at the standard dose.3PubMed Central. Efficacy of different doses of ketamine as a bolus in major depressive disorder This was a single study with a specific bolus (rather than infusion) design, so it hasn’t overturned the broader consensus, but it suggests the dose-response curve may not be completely flat above 0.5 mg/kg.
The practical takeaway is that 0.5 mg/kg over 40 minutes is the dose with the strongest and most replicated evidence. Going higher generally adds side effects without clearly adding benefit. Going lower may still do something for some patients, but the data are less convincing.
How Often and How Many Infusions
A single ketamine infusion can lift depression symptoms within hours, but the effect typically fades within days to a couple of weeks. That’s why most treatment protocols involve a series of infusions. The acute phase usually consists of six infusions spread over two to three weeks. A head-to-head study found that giving infusions twice a week and three times a week produced similar antidepressant results over a 15-day period.4PubMed. A Double-Blind, Randomized, Placebo-Controlled, Dose-Frequency Study of Intravenous Ketamine in Patients With Treatment-Resistant Depression Most clinics now use a twice-weekly or thrice-weekly schedule, and the antidepressant effect tends to build over successive infusions rather than plateau after the first one.5PubMed. A systematic review and meta-analysis of the efficacy of intravenous ketamine infusion for treatment resistant depression: January 2009 – January 2019
In one controlled trial, about 59% of participants met response criteria after repeated infusions, and the median patient needed three infusions before experiencing a significant response.6PubMed. Single, Repeated, and Maintenance Ketamine Infusions for Treatment-Resistant Depression: A Randomized Controlled Trial That same trial moved responders into a weekly maintenance phase and found that once-weekly infusions held depression scores stable without further improvement or decline. This “maintenance” question is one of the least settled areas in ketamine treatment.
The Maintenance Problem
After the acute phase works, the question becomes: how do you keep the improvement? Stopping treatment altogether leads to relapse for most people, often within weeks. A systematic review across multiple routes of administration found that maintenance ketamine treatment does appear to sustain antidepressant effects, though the quality of the evidence is limited and researchers are still working out optimal schedules.7The Lancet Psychiatry. Maintenance ketamine treatment in depression: a systematic review
One recent systematic review of maintenance protocols found that patients on regular, fixed schedules relapsed at lower rates (around 27%) compared to those on more variable, as-needed protocols (around 46%).8PubMed. Efficacy and safety of ketamine maintenance therapy in treatment-resistant depression: A systematic review of treatment protocols and clinical outcomes The practical translation is that spacing infusions out to every one to four weeks on a consistent schedule seems to work better than waiting until symptoms return and then scrambling for a booster. But no large randomized trial has definitively established the ideal long-term schedule, so most clinicians adjust frequency based on how a given patient responds.
Intranasal Esketamine Is a Different Drug and a Different Protocol
Esketamine is the S-enantiomer of ketamine and is roughly 1.5 times more potent as an anesthetic than the R-enantiomer (arketamine).9PubMed Central. Ketamine, Esketamine, and Arketamine: Their Mechanisms of Action and Applications in the Treatment of Depression and Alleviation of Depressive Symptoms When people refer to “Spravato,” they mean the FDA-approved esketamine nasal spray, which uses fixed doses of 56 mg or 84 mg rather than weight-based dosing. This is paired with a newly started oral antidepressant and administered in a clinical setting where patients are monitored for at least two hours.
The pivotal trial (TRANSFORM-2) using flexible dosing of 56 or 84 mg showed that esketamine plus a new antidepressant produced significantly greater improvement on a standard depression scale compared to antidepressant plus placebo nasal spray over 28 days.10PubMed. Efficacy and Safety of Flexibly Dosed Esketamine Nasal Spray Combined With a Newly Initiated Oral Antidepressant in Treatment-Resistant Depression A companion trial (TRANSFORM-1) using fixed doses tested 56 mg and 84 mg separately; the 84 mg dose narrowly missed statistical significance against placebo, while the 56 mg dose showed a nominally significant benefit but couldn’t be formally tested due to the study’s statistical hierarchy.11International Journal of Neuropsychopharmacology. Efficacy and Safety of Fixed-Dose Esketamine Nasal Spray Combined With A New Oral Antidepressant in Treatment-Resistant Depression: Results of a Randomized, Double-Blind, Active-Controlled Study (TRANSFORM-1) The most common side effects at both doses were nausea, dissociation, dizziness, and headache.
The esketamine prescribing schedule follows a structured taper: twice a week for the first four weeks, then once a week for the next four, then once every one to two weeks afterward. This stands in contrast to IV ketamine clinics, where there is no FDA-approved protocol and schedules vary by provider. Esketamine is the only ketamine-based product with formal FDA approval for treatment-resistant depression, a distinction that matters for insurance coverage and regulatory oversight.12PubMed. Practical recommendations for the management of treatment-resistant depression with esketamine nasal spray therapy
Other Routes and Their Dose Ranges
Not everyone receives ketamine through an IV or a nasal spray. Oral, intramuscular (IM), and subcutaneous (SC) routes each get the drug into the body differently, and the doses need to reflect that.
Oral ketamine has low bioavailability because the liver metabolizes much of it before it reaches the bloodstream. Oral doses in depression studies have ranged from 0.5 to 1.25 mg/kg, considerably higher than IV doses to compensate for that first-pass metabolism.13PubMed. Oral ketamine for depression: An updated systematic review Sublingual (under the tongue) lozenges partially bypass the liver and are commonly used in ketamine-assisted psychotherapy settings, with doses varying widely across clinics.
IM and SC injections bypass the gut entirely. A pharmacokinetic study estimated that both routes have roughly 64% bioavailability compared to IV.14PubMed Central. Population Pharmacokinetics and Pharmacodynamics of the Therapeutic and Adverse Effects of Ketamine in Patients With Treatment-Refractory Depression IM ketamine is used in some psychotherapy models, particularly at higher doses (around 1.5 to 2.0 mg/kg) intended to produce a deeper altered state, while lower IM or sublingual doses are used for sessions where more verbal exchange between patient and therapist is desired.15PubMed Central. Ketamine for the treatment of mental health and substance use disorders: comprehensive systematic review – Section: Route of administration, dose and therapeutic support The variability in dose and route across ketamine-assisted psychotherapy studies is striking: one systematic review cataloged protocols ranging from a single 0.2 mg/kg IM injection to multiple five-day continuous IV infusions.16PubMed Central. Ketamine Assisted Psychotherapy: A Systematic Narrative Review of the Literature
Body Weight Matters More Than You’d Think
Because the standard dose is weight-based (0.5 mg/kg), the accuracy of the weight used in the calculation matters. Most clinics simply use total body weight, but for overweight or obese patients, this may actually overdose relative to the drug’s distribution in the body. Ketamine is lipophilic, meaning it dissolves into fat tissue, but the relationship between body fat and the drug’s antidepressant action isn’t straightforward.
A recent study examined how different weight formulas affected the actual dose people received. Using ideal body weight (IBW) formulas instead of total weight resulted in doses that were lower than the standard 0.5 mg/kg calculation for nearly all participants, because most of the study group was overweight. Some patients ended up receiving as little as 51% to 58% of the intended dose when calculated against ideal weight.17PubMed Central. The quest for optimal ketamine dosing formula in treatment-resistant major depressive disorder A follow-up study in bipolar depression found a similar pattern, with lean body mass and body surface area calculations yielding lower relative doses, particularly among non-responders.18PubMed Central. Ketamine dosing formula in treatment-resistant bipolar depression The implication is that some patients who don’t respond may simply be getting too little drug for their body composition, but no consensus formula has replaced total body weight in clinical practice yet.
Dissociation During the Infusion
One of the more unsettling aspects of ketamine treatment is the dissociative experience: a feeling of detachment from your body or surroundings that peaks during the infusion and usually fades within an hour or two. There’s been a persistent question about whether dissociation is merely a side effect or is actually part of how the drug works.
Several studies have found a correlation between the intensity of dissociation and the degree of antidepressant response at 24 hours and sometimes at day seven.19Journal of Affective Disorders. Do the dissociative side effects of ketamine mediate its antidepressant effects? When researchers broke down the different types of dissociation, they found that depersonalization (feeling detached from yourself) was the component most consistently linked to antidepressant improvement, while amnesia was unrelated.20PubMed Central. Features of dissociation differentially predict antidepressant response to ketamine in treatment-resistant depression A more recent secondary analysis found that this relationship held for mild-to-moderate dissociation but plateaued at higher intensities, and the correlation was limited to the 24-hour time point rather than persisting to day seven.21PubMed Central. Does the intensity of dissociation predict antidepressant effects 24 hours after infusion of racemic ketamine or esketamine in treatment-resistant depression?
What this means practically: experiencing some dissociation during an infusion is normal and may be a sign the drug is engaging the right brain circuits. But chasing a more intense trip by pushing the dose higher isn’t supported by the evidence. The correlation is modest and doesn’t hold beyond a day or two, and higher doses add cardiovascular and psychological side effects.
Benzodiazepines Can Blunt the Effect
If you’re already taking a benzodiazepine like lorazepam, clonazepam, or diazepam, your response to ketamine may be weaker. Multiple analyses have flagged this interaction. In one case report, a patient’s antidepressant response to ketamine lengthened from a few days to one to two weeks after lorazepam was discontinued. Across several post-hoc analyses and a study of 47 patients, benzodiazepine use was consistently associated with delayed time to response, faster relapse, and lower odds of responding at all. Higher benzodiazepine doses predicted worse outcomes, with doses above a certain threshold significantly predicting non-response.22PubMed Central. Pharmacodynamic Interactions Between Ketamine and Psychiatric Medications Used in the Treatment of Depression: A Systematic Review – Section: Results / Benzodiazepines
A 2026 naturalistic study of subcutaneous esketamine confirmed the pattern: concurrent benzodiazepine use was associated with higher depression scores throughout treatment. Interestingly, lamotrigine and lithium did not show the same negative interaction.23PubMed. Role of concomitant benzodiazepines, lithium, and lamotrigine in modulating the antidepressant effects of subcutaneous esketamine in patients with treatment-resistant depressive episodes This matters because many patients with treatment-resistant depression are already on benzodiazepines for anxiety. The evidence doesn’t say you can’t receive ketamine while on a benzodiazepine, but it suggests your clinician should be aware of the interaction and may want to taper your benzodiazepine dose if safely possible before starting ketamine.
Bipolar Depression
Ketamine for unipolar depression gets most of the attention, but it also shows promise in bipolar depression, where treatment options are more limited and traditional antidepressants carry a risk of triggering manic episodes. All published studies in bipolar depression have used the same 0.5 mg/kg IV dose alongside a mood stabilizer. A systematic review of six studies found an overall response rate of about 61% for ketamine compared to 5% for placebo.24International Journal of Neuropsychopharmacology. Ketamine for Bipolar Depression: A Systematic Review
A notable concern was whether ketamine might flip patients into mania. A scoping review found that side effects in bipolar patients were similar to those in unipolar depression (dizziness, dissociation, nausea) and that manic switching rates were not elevated compared to unipolar patients. However, there were signals that the risk may be higher in patients already on antidepressants.25PubMed Central. The Role of Ketamine in the Treatment of Bipolar Depression: A Scoping Review – Section: Safety and Tolerability of Ketamine Use in Bipolar Depression A 2026 randomized trial of serial ketamine infusions in treatment-resistant bipolar depression found significant improvement over midazolam placebo, with no cases of mania, hypomania, or psychosis in either group.26JAMA Psychiatry. Serial Ketamine Infusions for Treatment-Resistant Bipolar Depression: A Randomized Clinical Trial The dose and schedule (0.5 mg/kg, administered serially) were consistent with what’s used in unipolar depression, suggesting no special dosing adjustment is needed for bipolar patients as long as a mood stabilizer is on board.
Older Adults and Blood Pressure
Ketamine raises blood pressure and heart rate transiently, which is well tolerated in most younger and middle-aged adults but raises questions for older patients. A pilot study in adults over 60 with late-life treatment-resistant depression found that a quarter of participants experienced transient infusion-related hypertension, and about a third received preventive clonidine before every infusion as a precaution. No infusions had to be stopped because of elevated blood pressure or other adverse events.27PubMed Central. Intravenous Ketamine for Late-Life Treatment-Resistant Depression: A Pilot Study of Tolerability, Safety, Clinical Benefits, and Effect on Cognition The dose used was the standard 0.5 mg/kg, suggesting that the approach doesn’t require dose reduction in older adults so much as closer cardiovascular monitoring and potentially a pre-treatment blood pressure medication.
How Ketamine Works in the Brain
Traditional antidepressants take weeks to kick in because they work through slow changes in serotonin or norepinephrine signaling. Ketamine operates on an entirely different system. It blocks a type of glutamate receptor called the NMDA receptor. This blockade triggers a cascade that results in the rapid production of new proteins at synapses, including a growth factor called BDNF, which strengthens connections between neurons.28PubMed. Synaptic mechanisms underlying rapid antidepressant action of ketamine This burst of synaptic plasticity, particularly in the hippocampus, appears to be what produces the rapid mood improvement.29PubMed Central. Bridging rapid and sustained antidepressant effects of ketamine The speed of this process, hours rather than weeks, is what makes ketamine fundamentally different from conventional antidepressants.30PubMed Central. Ketamine and the Future of Rapid-Acting Antidepressants
The Search for Biomarkers That Predict Response
One of the biggest frustrations in ketamine treatment is the inability to predict who will respond before starting. Researchers have investigated a broad range of potential biomarkers, from brain imaging patterns and EEG signals to blood-based markers involving inflammation, stress hormones, and genetic variations.31PubMed Central. Neurobiological biomarkers of response to ketamine A 2025 study looking at frontal EEG patterns found that connectivity and entropy measures in the brain’s frontal regions could discriminate between responders and non-responders with moderate accuracy.32PubMed. The role of frontal EEG in predicting clinical response of major depressive disorder to intranasal ketamine and esketamine That said, none of these biomarkers are ready for clinical use. The effect sizes are modest, and no single test can reliably tell a clinician whether to proceed with ketamine or try something else. For now, the only practical predictor of ketamine response is trying ketamine and seeing what happens across the first few infusions.
Addiction Risk in Therapeutic Settings
Ketamine is a Schedule III controlled substance with known recreational abuse potential, which understandably concerns both patients and providers. A systematic review looking specifically at addiction risk during ketamine depression treatment found that clear signs of tolerance or dependence were rare: out of all the patients studied, only four individuals were reported to exhibit clear signs of tolerance to the antidepressant effect or dependence on the drug.33SAGE Journals (Journal of Psychopharmacology). Is there a risk of addiction to ketamine during the treatment of depression? A systematic review of available literature The distinction between therapeutic and recreational use is important here. Therapeutic doses are lower, administered in clinical settings, and given at intervals. Recreational users tend to consume much higher amounts much more frequently. The urinary tract damage that has been linked to ketamine, for example, is associated with heavy recreational use rather than the subanesthetic doses used in depression treatment.34PubMed Central. Ketamine bladder syndrome: an important differential diagnosis when assessing a patient with persistent lower urinary tract symptoms That said, long-term safety data on maintenance ketamine for depression are still limited, and the Lancet Psychiatry review noted that while tachyphylaxis, cognitive impairment, and serious urinary problems seem uncommon so far, the studies to date are small and methodologically limited.35The Lancet Psychiatry. Maintenance ketamine treatment in depression: a systematic review Patients with a history of substance use disorders deserve particular caution, and ongoing monitoring is warranted for anyone on a long-term maintenance protocol.