Yes. Using Champix can result in side effects, although not everyone will necessarily experience them.

It’s perhaps worth noting too that many people may experience certain 'side effects' (or rather, symptoms related to nicotine withdrawal) to some extent when giving up smoking, whether they use medication or not.

The prospect of withdrawal symptoms shouldn't put you off trying to quit. These will only be temporary, and giving up smoking is much better for your health in the long term. 

Using medication does carry a risk of side effects; so it’s important to know about them before commencing stop smoking treatment. If Champix is not suitable for you, your doctor may suggest an alternative.

On this page, we’ll discuss some of the side effects associated with Champix, and how often they are thought to occur, in more detail.

How does Champix work?

Cigarettes contain nicotine, a chemical that can have a profound effect on the brain. When someone inhales nicotine from smoking a cigarette, nicotine receptors in the brain release another chemical called dopamine, which is linked to feelings of pleasure and reward.

When someone smokes regularly, these receptors become used to a steady supply of nicotine; so when someone who smokes regularly doesn’t smoke, this leads to cravings.

The active ingredient in Champix is varenicline. This works on nicotinic receptors in the brain, to help alleviate cravings when someone gives up smoking.

It also stops nicotine inhaled from cigarette smoke from acting on these receptors, in effect preventing the process in the brain that leads to reward.

Champix side effects

All types of medication, whether prescribed by a doctor or bought over-the-counter, can cause side effects. Not everyone will experience them, and some will only experience mild symptoms.

Nonetheless, it is still important to be aware of the potential side effects associated with a treatment, in case you do encounter them and need to seek medical help.

Very common

In clinical trials prior to release, the most common side effect among patients taking the 1mg dose (following an introductory period of titration with the 0.5mg dose) was nausea; this occurred in 28.6% of cases. Mild to moderate levels of nausea tended to be reported early on in the course, and only rarely led to users stopping the treatment.

Headache, abnormal dreams and difficulty sleeping are also recorded as very common. According to the patient information leaflet, more than one in 10 users may experience these side effects.

Some Champix users who experience these secondary effects are able to offset them by taking their medication after a meal and with a full glass of water, or by not leaving it too late into the evening to take their dose. For others, these side effects are tolerable and may reduce over time.


Among the common side effects (affecting up to one in 10 users) listed are:

  • chest infection
  • sinus inflammation
  • change in appetite and the way foods taste
  • weight gain
  • sleepiness
  • heartburn
  • vomiting
  • bowel problems such as diarrhoea or constipation
  • indigestion, abdominal pain or bloatedness
  • toothache
  • skin rash
  • aching joints or muscles


Affecting up to one in 100 people, uncommon side effects listed include:

  • fungal or viral infection
  • anxiety, restlessness, mood swings, depression, aggressive behaviour
  • seeing things that aren’t there
  • changes in libido
  • problems thinking
  • seizure
  • tremor
  • sluggishness,
  • feeling less sensitive to touch
  • eye pain and infection
  • tinnitus
  • changes in heart rate and palpitations
  • hot flushes
  • blood pressure changes
  • nasal inflammation or congestion
  • hay fever
  • passing blood in stools
  • acne
  • muscle spasms
  • increased urinary frequency
  • heavy menstrual bleeding
  • flu symptoms
  • heart attack
  • hyperglycaemia


Side effects listed as rare (up to one in 1,000 users) include:

  • feeling excessively thirsty
  • low mood
  • slow thinking
  • stroke
  • loss of coordination
  • sleep problems
  • sight problems
  • irregular heartbeat
  • pain in the throat
  • snoring
  • blood in vomit
  • joint stiffness
  • diabetes
  • high sugar concentration in urine
  • discharge from the vagina
  • cyst
  • abnormal behaviour
  • skin reactions including Stevens-Johnson Syndrome
  • severe allergic reactions

More information

Full details on the side effects recorded in Champix use can be found in the patient information leaflet (PIL). If you have any concerns about the side effects mentioned here you should contact your doctor.

Side effects can reported to your doctor, pharmacist or directly through the Yellow Card scheme. The scheme allows anyone to report adverse drug reactions and helps the Medicines and Healthcare products Regulatory Agency (MHRA) identify any potential problems and carry out appropriate investigations.

Changes in behaviour

Deciding to quit smoking can put pressure on your mental well being whether you quit with or without the help of medication. The addictive properties of nicotine mean that it can take some time for the brain to adjust, thus producing withdrawal symptoms.

The PIL and the summary of product characteristics (SPC) for Champix state that there is a possibility that users may experience changes to the way they think or behave.

Changes in thoughts and behaviour that have been noted include symptoms such as depression, agitation, suicidal thoughts, loss of contact with reality and psychosis.

It is important to inform your close family when you decide to commence smoking cessation therapy. Patients who notice changes in their thinking or behaviour should contact their doctor.

Stopping Champix

When you start a course of Champix your doctor will explain how you should take the medication. Most people take one tablet once a day for the first three days, followed by one tablet taken twice a day (one in the morning and one in the evening) for the next 12 weeks. The dosage may vary during this time.

If after 12 weeks you have stopped smoking your doctor may advise you to continue with another 12 weeks of Champix treatment to help keep any withdrawal symptoms at bay.

Suddenly stopping Champix without consulting your doctor may put you at risk of relapse. You should continue with your course of Champix as directed by your doctor.

At the end of a course of Champix it is possible to experience strong urges to smoke, increased irritability, sleep disturbance and depression. A staggered lower dose may be advised by your doctor to try and reduce the likelihood of these symptoms.

If you have concerns about stopping your smoking cessation course then you should speak to your doctor.

While Champix can help someone to give up smoking, it is much more likely to be effective if they are dedicated and motivated to quit.

You should not stop your treatment without speaking to your doctor, as doing so can leave you vulnerable to smoking cravings and side effects.

If at any point you experience side effects which you are unable to tolerate, you should speak to your doctor. In some circumstances they may suggest a lower dose.

Page last reviewed:  24/12/2020 | Next review due:  10/10/2021