Risperidone Side Effects: What to Expect and When to Call Your Doctor

Starting any new psychiatric medication comes with questions — and risperidone is no exception. Understanding which side effects are common and expected, which ones require monitoring, and which are emergencies can help you stay safe and informed. This guide covers everything you need to know about risperidone side effects in plain language.

The Boxed Warning: Increased Risk in Elderly Dementia Patients

Before anything else: risperidone carries a FDA Boxed Warning (the most serious warning level) for increased risk of death in elderly patients with dementia-related psychosis. Risperidone is NOT approved for treating behavioral symptoms in elderly patients with dementia. If you or a loved one has dementia, this medication should not be used for that purpose. This warning does not apply to adults with schizophrenia, bipolar disorder, or children with autism-related irritability.

Common Side Effects (Manage, Don't Panic)

These side effects are reported frequently and are generally manageable. Most improve over the first few weeks as your body adjusts:

• Sedation and drowsiness: Very common, especially at the start of treatment or after dose increases. Taking your full dose at bedtime can help.
• Weight gain: Risperidone can cause meaningful weight gain, particularly in the first 6 months of treatment. Monitor your weight monthly and discuss healthy diet and exercise strategies with your provider.
• Extrapyramidal symptoms (EPS): Tremors, muscle stiffness, restlessness (akathisia), or slowed movement. EPS is more likely at higher doses. Tell your doctor if you feel this way — dose adjustments or adding a medication like benztropine can help.
• Hyperprolactinemia: Risperidone raises prolactin levels more than most other atypical antipsychotics. This can cause breast swelling or tenderness, unusual breast milk production, irregular periods, decreased sex drive, or erectile dysfunction. These effects usually improve with dose reduction or switching medications.
• Orthostatic hypotension: A drop in blood pressure when standing up, causing dizziness or lightheadedness. Most common when starting treatment. Rise slowly from seated or lying positions, especially first thing in the morning.
• Headache, nausea, or stomach upset: Often transient and improve within 1–2 weeks. Taking risperidone with a small amount of food may help if stomach upset is bothersome.
• Nasal congestion: A stuffy or runny nose is a commonly reported side effect, particularly early in treatment.

Serious Side Effects: Monitor Closely

These side effects are less common but require medical attention if they occur:

• Metabolic changes: Risperidone can elevate blood sugar and cholesterol. Your doctor should monitor fasting blood glucose and lipids periodically.
• Tardive dyskinesia (TD): A movement disorder characterized by involuntary, repetitive movements of the face and body (tongue thrusting, lip smacking, grimacing). Risk increases with long-term use and higher doses. TD may be irreversible. Report any abnormal movements to your doctor immediately.
• Low blood cell counts: Risperidone can rarely reduce white blood cells (leukopenia/neutropenia). Seek medical attention if you develop fever, chills, or signs of infection.
• Priapism: A painful, prolonged erection (4+ hours) that is a medical emergency. Go to the emergency room immediately if this occurs.

Emergency Symptoms: Call 911 or Go to the ER

These symptoms require emergency medical care immediately:

• Neuroleptic malignant syndrome (NMS): Extremely rigid muscles, very high fever, sweating, confusion, fast or irregular heartbeat, tremors. NMS is rare but potentially fatal and requires immediate ER care.
• Severe allergic reaction: Hives, difficulty breathing, swelling of the face, lips, tongue, or throat. Stop the medication and call 911.
• Signs of stroke: Sudden numbness, face drooping, arm weakness, speech difficulty. Call 911 immediately.
• High blood sugar emergency: Extreme thirst, frequent urination, fruity-smelling breath, nausea, confusion. Hyperglycemia can lead to diabetic ketoacidosis, which is life-threatening.

Temperature Sensitivity

Risperidone can impair your body's ability to regulate temperature. Avoid getting overheated during exercise or hot weather — overheating can lead to heat stroke. Also avoid getting too cold. Stay hydrated, especially in summer months.

What Routine Monitoring Should My Doctor Do?

Your prescriber should monitor the following at regular intervals while you're on risperidone:

• Weight and BMI (baseline and at least every 4 weeks for the first 12 weeks, then quarterly)
• Fasting blood glucose and HbA1c (baseline and annually; more often if diabetic or at-risk)
• Fasting lipids (baseline and annually)
• Blood pressure (at each visit for the first several months)
• Abnormal involuntary movement screening (AIMS scale) for tardive dyskinesia at least every 6–12 months

The Bottom Line

Risperidone is an effective medication, but it comes with side effects that require awareness and monitoring. Most common side effects are manageable — sedation, EPS, and weight gain tend to improve over time or respond to dose adjustments. Serious effects like NMS or tardive dyskinesia require prompt medical attention. Always attend your follow-up appointments and report any new or worsening symptoms to your prescriber. For information on drug interactions that can make side effects worse, see our guide on risperidone drug interactions.