What You Should Know About Ketamine Side Effects Before Starting Treatment

Ketamine is a powerful medication that can produce significant benefits for treatment-resistant depression, chronic pain, and other conditions. But like all medications, it comes with side effects — some expected and manageable, others that require immediate medical attention.

Whether you're getting IV infusions at a clinic, taking compounded lozenges at home, or receiving Spravato (Esketamine) nasal spray, understanding the side effects upfront helps you prepare and know when to speak up.

What Is Ketamine?

Ketamine is an FDA-approved anesthetic (brand name Ketalar) classified as a Schedule III controlled substance. It works by blocking NMDA receptors in the brain, and at lower doses, it produces rapid antidepressant effects that have made it increasingly popular for mental health treatment. For a detailed overview, see our guide on what Ketamine is and how it's used.

Common Side Effects of Ketamine

Most people experience some side effects during or shortly after Ketamine treatment. These are generally mild and resolve within a few hours:

• Dissociation or dream-like feelings — This is the most characteristic effect. You may feel detached from your body or surroundings. It's usually temporary and fades within 1–2 hours.
• Dizziness — Feeling lightheaded or unsteady is common, especially when standing up. Stay seated or lying down during and after treatment.
• Nausea and vomiting — Reported in up to 25% of patients. Many providers offer anti-nausea medication beforehand to reduce this.
• Increased blood pressure — Ketamine typically raises blood pressure by 20–30%, which is why providers monitor your vitals during sessions.
• Increased heart rate — Your heart may beat faster than usual. This is temporary and generally resolves as the medication wears off.
• Blurred or double vision — Vision changes are common during treatment and usually clear within a couple of hours.
• Drowsiness — You'll likely feel sleepy after treatment. Don't drive or operate heavy machinery for at least 24 hours after a session.
• Confusion — Some mental fogginess is normal during and shortly after treatment. It typically clears as the Ketamine leaves your system.
• Emergence reactions — Vivid dreams, hallucinations, or a sense of floating may occur as the medication wears off. These happen more frequently at higher doses.
• Anxiety or agitation during recovery — Some patients feel anxious or restless as the effects subside. This usually passes within an hour.

Serious Side Effects — When to Call Your Doctor

While rare, some Ketamine side effects are serious and require immediate medical attention. Contact your doctor or seek emergency care if you experience:

• Severe breathing problems — Respiratory depression can occur, especially with higher doses or rapid IV administration. If you feel like you can't breathe or your breathing becomes very slow, this is an emergency.
• Dangerous blood pressure spikes — If you experience a severe headache, chest pain, or visual changes after treatment, your blood pressure may be dangerously high.
• Slow heart rate (bradycardia) — While increased heart rate is common, an abnormally slow heart rate can also occur and may require medical intervention.
• Laryngospasm — A sudden tightening of the vocal cords that makes it hard to breathe. This is rare but serious, most commonly seen with injectable Ketamine in clinical settings.
• Severe allergic reaction — Signs include difficulty breathing, swelling of the face or throat, hives, or a rapid drop in blood pressure. Seek emergency care immediately.
• Bladder problems — Chronic Ketamine use can cause ulcerative or interstitial cystitis. Symptoms include painful urination, frequent urination, blood in urine, or pelvic pain. Report any urinary symptoms to your provider right away.
• Seizure-like movements — Involuntary muscle movements or jerking can occur. While not always true seizures, they should be reported to your doctor.
• Signs of psychological dependence — If you feel a strong urge to use Ketamine outside of your prescribed treatment, cravings between sessions, or difficulty stopping, talk to your provider immediately.

Side Effects in Specific Populations

Elderly Patients

Older adults may be more sensitive to Ketamine's effects on blood pressure and cognition. Providers typically use lower doses and monitor more closely.

Pregnant or Nursing Women

Ketamine is classified as Pregnancy Category B — animal studies showed no harm, but there are no adequate human studies. It crosses the placenta and is not recommended during pregnancy or labor unless clearly needed. Discuss risks with your doctor.

Patients With Substance Use History

Because Ketamine is a Schedule III controlled substance with potential for psychological dependence, patients with a history of substance abuse should be closely monitored. Your provider may recommend more frequent check-ins or choose an in-clinic treatment route over at-home formulations.

Patients With Heart Conditions

Ketamine raises blood pressure and heart rate. It is contraindicated in patients with uncontrolled hypertension, aneurysms, or severe cardiovascular disease. If you have any heart condition, make sure your Ketamine provider is aware before starting treatment.

How to Manage Common Side Effects

Here are practical tips to reduce discomfort during Ketamine treatment:

• Fast before treatment — Eating a light meal 4–6 hours before your session can reduce nausea. Some providers recommend fasting for 4 hours before IV or IM sessions.
• Ask about anti-nausea medication — Ondansetron (Zofran) is commonly given before Ketamine to prevent nausea and vomiting.
• Stay hydrated — Drink plenty of water before and after your session.
• Arrange a ride — You should not drive for at least 24 hours after a Ketamine session. Plan transportation in advance.
• Bring comfort items — An eye mask, comfortable headphones, or a calming playlist can help manage the dissociative experience.
• Communicate with your provider — If side effects are bothersome, your dose or infusion rate may be adjusted. Don't suffer in silence.
• Report urinary symptoms early — Bladder toxicity is dose-dependent and more common with frequent use. Catching it early can prevent permanent damage.

For more on how Ketamine works in your body and why these side effects occur, read our article on Ketamine's mechanism of action explained in plain English.

Final Thoughts

Most Ketamine side effects are temporary and manageable, especially when treatment is supervised by an experienced provider. The dissociative feelings and dizziness that many patients experience are actually expected parts of the treatment and typically resolve within a few hours.

The key is knowing the difference between normal side effects and warning signs that need medical attention. Keep this list handy, communicate openly with your provider, and don't hesitate to call if something feels wrong.

If you're considering Ketamine treatment and want to find a provider, check out our guide on how to find a Ketamine doctor near you. And if cost is a concern, we've covered how to save money on Ketamine as well.

Need help finding Ketamine near you? Search Medfinder to check availability at pharmacies in your area.