Risperidone Side Effects: Prolactin, Weight, and Movement Effects

You started risperidone because something needed to change, and maybe it did. Then the scale crept up, or your period stopped, or your legs wouldn’t stay still. When side effects start, it can feel like you’re on your own until the next appointment, and the next appointment is weeks away.

Risperidone is thought to work by blocking dopamine D2 receptors, along with serotonin 5-HT2 receptors, according to the FDA label for Risperdal. Dopamine has more than one job in your body. In the brain’s mood and thinking circuits, blocking it helps treat psychosis and mania. In the pituitary gland, dopamine is the brake on prolactin, and in movement circuits, it keeps motion smooth. A drug that blocks D2 can’t do it in only one place, which is why risperidone’s side effects follow the biology with real precision.

Risperidone belongs to the second-generation, or atypical, antipsychotics, which largely replaced older drugs known for movement problems. That shift helped: a tardive dyskinesia meta-analysis of 41 studies found tardive dyskinesia in 20.7% of people currently on second-generation antipsychotics, compared with 30.0% on first-generation drugs. Risperidone is FDA-approved for schizophrenia, bipolar mania, and irritability in autism, and it has decades of trial data behind it. The results are real, and the science is well established.

But a lower risk than older drugs still leaves plenty to watch, and at Siggy we’d rather hand you a monitoring calendar than leave side effects for the next quarterly visit.

Monitoring-led care means knowing which effects to expect, checking the right numbers at the right weeks, and acting on changes early. It addresses the same goal, a medication that keeps working, with fewer surprises. The difference is measured, and those measurements are clinical evidence.

What This Page Covers

• What Are the Most Common Risperidone Side Effects?
• How Does Risperidone Affect Prolactin?
• How Much Weight Gain Does Risperidone Cause?
• What Movement Side Effects Can Risperidone Cause?
• What Monitoring Should You Expect on Risperidone?
• When Should You Call Your Prescriber or 911?
• How Siggy Fits In
• Start Your Anonymous Intake

What Are the Most Common Risperidone Side Effects?

The FDA label lists the most common side effects in clinical trials as those seen in at least 5% of people and at twice the placebo rate. They include:

• Movement effects: stiffness and slowed movement (parkinsonism), restlessness (akathisia), muscle spasms (dystonia), and tremor
• Sleepiness, fatigue, and dizziness
• Nausea, constipation, indigestion, and dry mouth or extra saliva
• Increased appetite and weight gain
• Anxiety, blurred vision, and nasal congestion

Many of these scale with dose. In adult schizophrenia trials, doses above 6 mg a day given twice daily weren’t more effective than lower doses but caused more movement side effects, so the label generally doesn’t recommend them. Sleepiness is common early, and in the label’s pediatric autism trials it usually peaked in the first two weeks and lasted a median of 16 days.

Risperidone can also lower blood pressure when you stand up, causing dizziness or fainting, especially during the first dose increases. Getting up slowly helps, and a slower start is one reason prescribers titrate gradually.

How Does Risperidone Affect Prolactin?

Prolactin is the hormone that triggers breast milk production. Dopamine normally keeps it low, so blocking dopamine in the pituitary lets prolactin rise. The label is direct about this: risperidone raises prolactin more than other antipsychotics, and the elevation persists with long-term use.

Large comparisons agree. A Lancet network meta-analysis of 32 antipsychotics in 402 trials found the biggest prolactin increase with paliperidone, about 48.5 ng/mL above placebo. Paliperidone is risperidone’s main active metabolite, the form your body converts it into, so the two share this profile.

High prolactin can show up as:

• Irregular or missed periods, and reduced fertility while prolactin stays high
• Milky nipple discharge (galactorrhea)
• Breast enlargement in men (gynecomastia)
• Lower sex drive or erectile problems
• Lower bone density over time, when high prolactin suppresses sex hormones

Young people are especially affected. In placebo-controlled trials in children and teens with bipolar disorder or schizophrenia, 82% to 87% of those on risperidone had elevated prolactin, compared with 3% to 7% on placebo.

Elevated prolactin isn’t always a reason to stop. A management review for psychiatric pharmacists found the strongest evidence for switching to or adding aripiprazole, with less evidence for lowering the dose, switching to another lower-prolactin antipsychotic, or adding a dopamine agonist. In a network meta-analysis of add-on treatments covering 62 trials, low-dose aripiprazole (under 5 mg a day) produced the largest prolactin drop. Any change has to be weighed against the risk of symptoms returning, so it belongs with your prescriber.

How Much Weight Gain Does Risperidone Cause?

Weight gain on risperidone is real but uneven. In the label’s pooled adult trials lasting 3 to 8 weeks:

• People on 1 to 8 mg a day gained an average of 0.7 kg, compared with a 0.3 kg loss on placebo
• 8.7% gained at least 7% of their body weight, compared with 2.9% on placebo
• At more than 8 mg a day, 20.9% crossed that 7% line

Gain tends to continue past the first weeks. In longer studies, average weight change was 4.3 kg at 24 weeks and 5.3 kg at 48 weeks.

Children and teens gain more. In the label’s pediatric trials, 32.6% on risperidone gained at least 7% of body weight, compared with 6.9% on placebo. A JAMA cohort study of young people starting an antipsychotic for the first time found an average gain of 5.3 kg after about 11 weeks on risperidone, with a significant rise in triglycerides.

The label also warns about blood sugar and cholesterol changes with atypical antipsychotics, including rare but serious cases of diabetes. Watch for unusual thirst, frequent urination, extreme hunger, or weakness, and report them.

What Movement Side Effects Can Risperidone Cause?

Movement effects come in two timeframes. Early effects, known as extrapyramidal symptoms, include stiffness, tremor, restlessness, and muscle spasms. They’re dose-related. In one 8-week label trial, spontaneous reports of these symptoms rose from 13% on placebo to 17% at 2 mg, 21% at 6 mg, and 35% at 16 mg a day. Dystonia, a sudden muscle spasm that can affect the neck, jaw, or eyes, tends to appear in the first few days, and the label notes higher risk in males and younger people.

Akathisia deserves special mention because it’s easy to mistake for anxiety. It feels like an inner pressure to keep moving. If you can’t sit through a meal or feel like crawling out of your skin after a dose increase, tell your prescriber.

Tardive dyskinesia is the longer-term risk: involuntary movements, often of the lips, tongue, or face, that can be lasting. According to the label, risk grows with treatment length and total dose, but it can appear after brief use at low doses. It sometimes improves after stopping the drug. Treatment exists. In the KINECT 3 trial, valbenazine, a VMAT2 inhibitor, significantly reduced movement scores over 6 weeks in 225 people with moderate or severe tardive dyskinesia, most of whom kept taking their antipsychotic.

What Monitoring Should You Expect on Risperidone?

Checks catch problems while they’re still small. For second-generation antipsychotics, the ADA and APA consensus statement recommends the schedule below, as restated by pharmacists who audited real-world monitoring and found baseline checks were done for fewer than 30% of patients at one VA center.

What Gets Checked	When	What It Tracks
Weight or BMI	Baseline, weeks 4, 8, 12, then every 3 months	Weight gain
Blood pressure, fasting glucose	Baseline, week 12, then yearly	Diabetes and heart risk
Fasting lipid panel	Baseline, week 12, then periodically	Cholesterol, triglycerides
Waist size, personal and family history	Baseline, then yearly	Cardiovascular risk

The 2004 consensus allowed normal lipid results to be rechecked as rarely as every 5 years, but treat that as a minimum. Your prescriber may test more often based on your weight, family history, and other risk factors. The schedule also doesn’t cover two risperidone-specific issues, so ask about them too. Mention any period changes, nipple discharge, breast changes, or sexual side effects, since those can point to high prolactin. Ask whether your prescriber is checking for involuntary movements at follow-up visits.

One more check matters if you also take an antidepressant. The label says fluoxetine and paroxetine raise risperidone levels, so the risperidone dose should be lowered and kept at or below 8 mg a day with either one. Our SSRI comparison guide explains how these antidepressants differ.

When Should You Call Your Prescriber or 911?

Call 911 for high fever with stiff muscles and confusion, which can signal neuroleptic malignant syndrome, a rare emergency. Also call 911 for fainting, a seizure, trouble breathing or swallowing, or a painful erection that won’t go away. Call or text 988 for thoughts of suicide or self-harm.

Contact your prescriber soon for:

• Restlessness that makes it hard to sit still
• New involuntary movements of the face, lips, or tongue
• Missed periods, nipple discharge, breast changes, or sexual problems
• Rapid weight gain, extreme thirst, or frequent urination
• Dizziness when standing, or sleepiness that affects driving or work

Don’t stop risperidone suddenly on your own. The label also carries a boxed warning: older adults with dementia-related psychosis who take antipsychotics have a higher risk of death, and risperidone isn’t approved for that use. For other antipsychotic side effect profiles, see our guide to Abilify side effects.

How Siggy Fits In

Most of risperidone’s important side effects are slow and quiet. Weight drifts, prolactin rises, and restlessness gets blamed on stress. Those are exactly the patterns a quick quarterly visit can miss.

Siggy’s licensed prescribers diagnose and treat the full range of mental health conditions. Siggy’s anonymous intake lets you list everything you take, with no name, email, or account required, so any treatment plan accounts for interactions like the fluoxetine and paroxetine effect above. A licensed prescriber reviews your intake before anything is prescribed, and you get a downloadable summary you can share with your psychiatrist or primary care clinician.

Siggy isn’t an emergency service. This article is for education only and isn’t a substitute for personal medical advice. Don’t start, change, or stop a medication without your prescriber. It reflects sources available as of October 2026.

Start Your Anonymous Intake

If you’re in crisis right now, call 911 or call or text 988 first. If you want a licensed prescriber to look at your symptoms alongside your other medications, start your anonymous intake. It’s free, there’s no name or email required, and a licensed prescriber reviews your intake before anything is prescribed. Your summary is yours to keep and share.