Ketamine dosing varies dramatically depending on what it’s being used for and how it enters the body. A dose for depression is roughly one-tenth of what’s used for surgical anesthesia, and the same milligram amount can have very different effects depending on whether it’s given intravenously, intranasally, or swallowed. Understanding these differences is essential because ketamine’s safety profile, while relatively wide, depends entirely on context.
Why the Route of Administration Changes Everything
When ketamine is injected directly into a vein, 100% of it reaches the bloodstream. Intramuscular injection delivers about 93% bioavailability. But when swallowed, only about 17% of the dose actually makes it into circulation because the liver breaks most of it down before it reaches the brain. This is why oral doses are measured in tens or hundreds of milligrams while IV doses for the same purpose might be a fraction of a milligram per kilogram of body weight. A 200 mg oral dose and a 35 mg IV dose in a 70 kg person can produce comparable effects, even though the numbers look wildly different.
IV Dosing for Depression
The most studied protocol for treatment-resistant depression uses 0.5 mg/kg delivered intravenously over 40 minutes. For a person weighing 70 kg (about 154 pounds), that’s 35 mg total. This is considered a subanesthetic dose, meaning it’s well below what would be needed for surgery. Treatments typically start at twice per week for an initial phase, then taper based on response.
Some clinics use higher doses. A naturalistic study of 77 inpatients found that doses of 0.75 to 1 mg/kg produced the most pronounced clinical effects, though higher doses also carry more side effects. After the initial phase of twice-weekly infusions over roughly five weeks, maintenance dosing is individualized. Research has explored several maintenance schedules: once weekly, every two weeks, or every three weeks, with twice weekly appearing most effective for sustaining improvement. The goal is finding the least frequent dosing that keeps symptoms at bay.
Nasal Spray (Esketamine) Dosing
The FDA-approved nasal spray, Spravato, uses esketamine, a more potent form of the ketamine molecule. Its dosing schedule is tightly structured. For treatment-resistant depression, the induction phase runs four weeks at 56 or 84 mg twice per week. Weeks five through eight drop to once weekly, and from week nine onward, frequency decreases to every two weeks or once weekly, whichever maintains the response.
For people with major depression and active suicidal thoughts, the protocol is different: 84 mg twice per week for four weeks, with the option to reduce to 56 mg if side effects are difficult. Treatment beyond four weeks for this specific indication hasn’t been systematically studied.
Every nasal spray session requires at least two hours of monitored observation in a clinic, including pulse oximetry, because of risks of sedation, dissociation, and changes in breathing. You cannot take this medication home or self-administer it outside a certified healthcare setting.
Dosing for Pain Management
Pain management uses a wider range of doses depending on whether the pain is acute or chronic and whether the patient has been on opioids. The standard subanesthetic approach starts with an IV bolus of 0.3 to 0.5 mg/kg, sometimes followed by a continuous infusion at 0.1 to 0.2 mg/kg per hour. Consensus guidelines from major anesthesia and pain medicine organizations recommend that bolus doses not exceed 0.35 mg/kg and that infusions stay under 1 mg/kg per hour outside of intensive monitoring settings.
Patients who are tolerant to opioids often require higher ketamine doses. In one large study of children, adolescents, and young adults, opioid-naive patients received infusions of 0.05 to 0.4 mg/kg per hour, while opioid-tolerant patients received up to 1 mg/kg per hour. The rationale for higher cumulative doses in chronic pain is that ketamine works by reversing the nervous system’s heightened sensitivity to pain signals, which takes more sustained exposure than simply blocking an acute pain episode.
Oral and Sublingual Dosing
Compounded oral ketamine, usually in the form of lozenges or troches, is increasingly prescribed for at-home use under medical supervision. Because oral bioavailability is so low (around 17%), doses are much higher in absolute milligram terms. A typical starting dose is 25 mg three times daily, with gradual increases based on tolerability and effect. In a long-term study of chronic pain patients, total daily doses ranged from 25 to 600 mg, with a median of 200 mg per day divided into three doses.
Sublingual administration, where the lozenge is held under the tongue or against the cheek rather than swallowed, likely improves absorption somewhat by allowing ketamine to enter the bloodstream through the mouth’s mucous membranes. However, some portion is inevitably swallowed, so bioavailability falls somewhere between the oral and IV figures.
Anesthetic Doses
Surgical anesthesia requires roughly 1 to 2 mg/kg intravenously, which is two to four times the depression dose. At these levels, ketamine produces full dissociative anesthesia, meaning the patient is unconscious and doesn’t feel pain but may keep breathing on their own, unlike most other anesthetics. This wide gap between therapeutic and anesthetic doses is part of what makes lower-dose protocols relatively safe. Ketamine’s lethal dose has been estimated at more than 100 times its effective dose, leading some researchers to suggest that lethal overdose from ketamine alone is “difficult or even impossible.”
Blood Pressure and Safety Thresholds
Ketamine reliably raises blood pressure and heart rate. This is the most common reason someone might not be a candidate for treatment. Guidelines recommend that patients with baseline blood pressure above 140/90 mmHg be evaluated carefully before proceeding. During an infusion, clinicians typically pause or stop treatment if systolic pressure exceeds 160 or diastolic exceeds 100. Some protocols use a higher threshold of 180/110 before intervening, particularly when there are no signs of organ stress like chest pain, vision changes, or confusion.
People with uncontrolled high blood pressure, aneurysms, significant heart valve disease, or advanced heart failure are generally excluded from ketamine treatment entirely. At every session, regardless of the dose or route, blood pressure, pulse, breathing rate, and oxygen levels should be monitored throughout and for a period afterward.
How Doses Compare Across Uses
- Depression (IV): 0.5 mg/kg over 40 minutes, twice weekly initially
- Depression (nasal spray): 56 or 84 mg per session, twice weekly tapering to every 1 to 2 weeks
- Acute pain (IV): 0.3 to 0.5 mg/kg bolus, then 0.1 to 0.5 mg/kg per hour
- Chronic pain (IV): infusions up to 1 mg/kg per hour in monitored settings
- Chronic pain (oral): 25 to 200 mg per dose, up to 600 mg daily in divided doses
- Surgical anesthesia (IV): 1 to 2 mg/kg
The pattern is consistent: depression protocols use the lowest IV doses, pain management sits in the middle, and anesthesia requires the highest. Oral routes always use larger milligram amounts to compensate for the liver’s aggressive first-pass metabolism. Every protocol assumes medical oversight, vital sign monitoring, and individualized adjustments based on how a patient responds.