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

Keppra (levetiracetam) is generally well tolerated compared to older anti-seizure medications, and it has a favorable safety profile that has made it one of the most prescribed seizure drugs in the United States. But like any medication, it does cause side effects in some patients — including some that require prompt medical attention. Here's a clear, honest guide to what to expect.

Most Common Side Effects of Keppra

The most common adverse reactions occurring at least 5% more often than placebo in adult clinical trials were:

Somnolence (drowsiness): Feeling sleepy or sluggish is one of the most reported effects, especially in the first 4 weeks of treatment. It often improves over time.

Asthenia (weakness/fatigue): A general sense of low energy or physical weakness.

Dizziness: Particularly when standing up quickly. Can affect coordination.

Headache: A common early side effect that typically subsides.

Infection: A slightly increased rate of common infections (like colds) was noted in clinical trials.

In pediatric patients, the most common effects are fatigue, aggression, nasal congestion, decreased appetite, and irritability. About 4% of patients in pre-approval trials dropped out due to CNS side effects. For most patients, these effects are most pronounced in the first month and improve with time.

Behavioral and Psychiatric Side Effects: The "Keppra Rage"

One of the most discussed side effects of levetiracetam is behavioral change — sometimes called "Keppra rage" by patients and caregivers. In clinical studies, 13% of adult patients and 38% of pediatric patients (ages 4–16) experienced non-psychotic behavioral symptoms including:

Aggression and irritability

Agitation and anxiety

Emotional lability (mood swings)

Depression or apathy

Hostility or personality changes

About 1% of patients experience serious psychiatric reactions (hallucinations, psychosis, or suicidal thoughts) that reverse after stopping the medication. The FDA requires all anti-seizure medications to carry a warning about increased risk of suicidal thinking and behavior. If you or a loved one on Keppra develops significant mood or behavior changes, contact your doctor promptly.

Serious Side Effects That Require Immediate Attention

While rare, the following side effects are serious and require you to stop taking Keppra and seek emergency care:

DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms): In December 2023, the FDA issued an alert about this rare but life-threatening reaction. It starts as a rash but can rapidly progress to fever, lymph node swelling, and internal organ injury (liver, kidneys, heart). Symptoms typically appear within 2–8 weeks of starting the medication. If you develop a new rash with fever or feel systemically unwell, stop Keppra and seek care immediately.

Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): Severe, potentially fatal skin reactions. Look for painful red/purple blisters, peeling skin, and sores on the mouth or eyes. The median time to onset is 14–17 days. If these symptoms appear, stop Keppra immediately and call 911 or go to the nearest emergency room.

Anaphylaxis / angioedema: Severe allergic reactions including face/throat swelling, hives, difficulty breathing, and low blood pressure. Can occur after the first dose or at any time during treatment. Call 911 immediately.

Suicidal thoughts or behaviors: Contact your doctor immediately if you experience thoughts of self-harm or suicide. This is a class-wide warning for all anti-seizure medications.

Important Warning: Do Not Stop Keppra Suddenly

Even if you experience side effects, do not abruptly stop taking Keppra without speaking to your doctor first. Sudden discontinuation of any anti-seizure medication can trigger withdrawal seizures, including life-threatening status epilepticus. If side effects are intolerable, your doctor will help you taper down gradually.

Special Considerations

Pregnancy: Levetiracetam is considered one of the safer anti-seizure medications in pregnancy. Prolonged clinical experience has not identified an increased risk of major birth defects compared to unexposed pregnancies. However, blood levels decrease during pregnancy (especially the third trimester), requiring dose monitoring.

Alcohol: Avoid or limit alcohol while taking Keppra. Both cause CNS depression, and combining them increases sedation and dizziness. Alcohol also lowers seizure threshold.

Renal impairment: Keppra is renally excreted. If you have kidney disease, your dose may need adjustment. Discuss with your doctor at each visit.

For more information on what medications and substances interact with Keppra, see our guide on Keppra drug interactions. And if you need help locating Keppra at a pharmacy near you, medfinder can help.