Side effects of varenicline

Varenicline may cause mild or serious side effects. More common mild side effects of varenicline and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about varenicline’s side effects, ask your doctor or pharmacist. You can also refer to the prescribing information for varenicline listed in the “Resources” section.

Mild side effects

More common mild side effects reported with varenicline are listed below.

This article doesn’t include all possible mild side effects of the drug. To learn more about varenicline’s side effects, refer to the prescribing information for varenicline listed in the “Resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Varenicline oral tablet’s mild side effects include:

nausea
dreams or nightmares that are unusual, strange, or vivid
constipation
gas
mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for varenicline” section.

Serious side effects

Serious side effects of varenicline are listed below.

This article doesn’t include all possible serious side effects of the drug. To learn more about varenicline’s side effects, refer to the prescribing information for varenicline listed in the “Resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, varenicline’s serious side effects include:

seizures
dizziness, which may lead to accidental injury or make driving unsafe
vision or hearing problems
depression
anxiety
agitation
mania* (periods of unusually high energy)
hallucinations* (seeing or hearing things that aren’t real)
suicidal thoughts or behaviors*
sleepwalking*
severe allergic reaction†

* These side effects weren’t reported in studies of varenicline. But they’ve occurred in people after the drug was approved for use.
† For details about this side effect, see the “Interactions and warnings for varenicline” section.

Suicide prevention

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

Call the 988 Suicide and Crisis Lifeline at 988.
Text HOME to the Crisis Textline at 741741.
Not in the United States? Find a helpline in your country with Befrienders Worldwide.
Call 911 or your local emergency services number if you feel safe to do so.

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.