Who Should Not Take Ketamine? Contraindications Explained

Who should not take ketamine? People with uncontrolled high blood pressure, active psychosis or schizophrenia, a known ketamine allergy, unstable cardiovascular disease, or elevated pressure inside the skull are generally not candidates for ketamine therapy. Several other groups, including people with an active substance use disorder, those who are pregnant or breastfeeding, and patients with unstable bipolar disorder, need extra caution and close provider oversight before starting treatment.

Ketamine therapy has helped many patients manage treatment-resistant depressionchronic pain, and anxiety, but it is not appropriate for everyone. This guide walks through the medical contraindications and risk factors a qualified provider screens for before approving ketamine treatment. If you recognize yourself in one of these categories, it does not automatically rule out ketamine for good. It means you need a thorough medical evaluation first.

Absolute Contraindications

These conditions generally rule out ketamine therapy because the safety risk is too high.

Uncontrolled High Blood Pressure

Ketamine can raise blood pressure, sometimes sharply. If your hypertension is not well controlled with medication, ketamine therapy carries a risk of dangerous blood pressure spikes that could lead to stroke, heart attack, or another cardiovascular emergency. According to the Mayo Clinic, ketamine's prescribing information lists uncontrolled hypertension as a specific precaution because the drug can cause dose dependent increases in blood pressure and heart rate. If your blood pressure is well controlled with medication and monitored by a physician, ketamine may still be an option once your provider consults with your cardiologist or primary care doctor.

Active Psychosis or Schizophrenia

Ketamine's dissociative and perception altering effects could worsen psychotic symptoms. Patients with active psychosis, including hallucinations, delusions, or severely disordered thinking, are generally not candidates for ketamine therapy. A well managed history of schizophrenia or schizoaffective disorder may be considered case by case by an experienced provider, but this requires careful evaluation and close monitoring.

Known Allergy to Ketamine

A true allergic reaction to ketamine is rare but is an absolute contraindication. If you have had hives, swelling, difficulty breathing, or anaphylaxis after ketamine exposure in the past, you should not receive ketamine therapy again.

Certain Cardiovascular Conditions

Several heart and vascular conditions make ketamine therapy risky:

• Unstable angina: chest pain from reduced blood flow to the heart that is not well controlled
• Recent heart attack (myocardial infarction), typically within the past three to six months
• Aortic aneurysm, an enlarged area in the aorta that could be affected by blood pressure changes
• Decompensated heart failure, meaning heart failure that is not adequately managed
• Recent stroke, typically within the past three to six months

If you have any cardiovascular history, a thorough cardiac evaluation should happen before ketamine therapy begins.

Increased Intracranial Pressure

Conditions involving elevated pressure inside the skull, such as certain brain tumors, hydrocephalus, or recent head trauma, may be worsened by ketamine. Ketamine was historically thought to raise intracranial pressure, though more recent evidence suggests the effect is smaller than once believed. Providers still treat this as a reason for caution.

Strong Relative Contraindications

These conditions do not automatically disqualify a patient, but they call for significant caution, close monitoring, and careful provider judgment.

Active Substance Use Disorder

If you are currently struggling with active substance abuse, particularly involving ketamine, other dissociatives, alcohol, or opioids, ketamine therapy generally should not begin until the substance use disorder is being actively addressed. The risk of misuse, the potential to complicate recovery, and the difficulty of judging ketamine's therapeutic effect during active substance use all argue for treating the substance use disorder first. The Substance Abuse and Mental Health Services Administration (SAMHSA), the federal agency that leads public health efforts on substance use and mental health, offers resources on safe treatment screening that can help patients and providers coordinate care. A history of substance use disorder that is in remission does not automatically disqualify you. Many providers treat patients in stable recovery, with appropriate monitoring and often in coordination with addiction treatment professionals.

Pregnancy and Breastfeeding

Ketamine's effects on fetal development are not well studied, so most providers will not administer ketamine therapy during pregnancy. Ketamine can also pass into breast milk. Most providers recommend against ketamine therapy while breastfeeding, or advise pumping and discarding breast milk for a period after each session. Discuss the risks and benefits with your provider and your obstetrician.

Unstable Bipolar Disorder

Ketamine has shown some promise for bipolar depression, but patients with unstable bipolar disorder, particularly those with a history of manic episodes triggered by antidepressant like medications, need careful evaluation. Ketamine could theoretically trigger a manic episode in susceptible individuals, though this appears uncommon. If you have bipolar disorder, your ketamine provider should work closely with your psychiatrist and have a plan for monitoring mood shifts.

Liver Disease and Thyroid Disorders

Ketamine is metabolized by the liver, so significant liver disease may change how your body processes the medication, potentially leading to higher than expected blood levels or prolonged effects. Patients with liver disease typically need dose adjustments and additional monitoring. Uncontrolled hyperthyroidism can also amplify ketamine's cardiovascular effects, particularly heart rate elevation, so a thyroid condition should be well managed before starting treatment.

Medication Interactions to Discuss

Certain medications can interact with ketamine or affect treatment decisions:

• MAO inhibitors (MAOIs): can potentially increase ketamine's blood pressure effects, so careful coordination is needed
• Benzodiazepines: some research suggests benzodiazepines may reduce ketamine's therapeutic effectiveness, so your provider may adjust timing or dose
• Lamotrigine: may reduce the dissociative effects of ketamine, which could affect therapeutic response
• Opioids: both ketamine and opioids affect respiratory function, so the combination requires careful monitoring, though ketamine may help some patients reduce opioid use over time
• CNS depressants: other sedating medications combined with ketamine can increase the risk of excessive sedation
• Stimulants: amphetamines and other stimulants combined with ketamine can increase cardiovascular strain

Always give your ketamine provider a complete list of everything you take, including prescription medications, over the counter drugs, supplements, and any recreational substances. For more on how providers evaluate these factors, see our guide to ketamine side effects and safety.

Age Considerations

Adolescents

Ketamine therapy for adolescents is an evolving area of practice. Some providers treat adolescents, typically age 13 and older, for severe, treatment resistant conditions, but the evidence base is smaller than it is for adults. If your child is being considered for ketamine therapy, confirm the provider has specific experience treating adolescent patients.

Older Adults

Older adults may be more sensitive to ketamine's cardiovascular and cognitive effects. Dose adjustments and additional monitoring are typically recommended for patients over 65. Pre-existing cardiovascular disease, cognitive decline, and polypharmacy, meaning the use of multiple medications, all call for careful evaluation.

When the Answer Is "Not Right Now"

If a provider tells you that ketamine therapy is not appropriate right now, that does not necessarily mean never. Many contraindications are manageable over time:

• High blood pressure can be brought under control with medication
• Substance use disorders can be treated, and stable recovery can open the door to ketamine therapy later
• Cardiovascular conditions can stabilize with treatment
• Medication adjustments can resolve interaction concerns

Work with your healthcare team to address whatever is currently making ketamine therapy inappropriate for you. Once you understand the process, our getting started guide and our list of questions to ask a ketamine provider can help you prepare for that conversation.