Clozapine | Atypical Antipsychotic For Schizophrenia

Medication name

Clozapine ("CLOZZ-a-peen")
Brand names

Clozaril® ("CLOZZ-a-ril")

Denzapin® ("DENZ-a-peen")

Zaponex® ("ZA-po-nex")
Medication type

Second generation antipsychotic (sometimes referred to as an ‘atypical antipsychotic’)

Tablets: 25mg, 50mg, 100mg, 200mg strengths

Orodispersible (‘melt in your mouth’) tablets: 12.5mg, 25mg, 50mg, 100mg, 200mg strengths

Liquids: 50mg per ml

If you are over 16 and have tried other medicines that have not worked, the doctor can prescribe clozapine for you as a licensed medicine for schizophrenia.

If you are under 16, a specialist doctor may still consider this as a treatment option.

Find out more about schizophrenia

About clozapine

Clozapine is a ‘second-generation antipsychotic’ (sometimes described as an ‘atypical antipsychotic’).

There is a naturally occurring chemical messenger ('neurotransmitter') in the brain called dopamine, which is mainly involved in thinking, emotions, behaviour and perception.

With some illnesses, dopamine may be overactive, which upsets the normal balance of chemicals in the brain and can produce a variety of symptoms.

Clozapine reduces dopamine activity where it is too high, helping with symptoms like hallucinations. It also adjusts dopamine levels in other areas of the brain to improve focus and concentration. Its effect on other brain chemicals makes it more effective and helps offset some movement-related and hormone-related side effects that other antipsychotics can produce.

Clozapine is only used to treat schizophrenia when other medicines have not worked well.

Why clozapine works better to treat schizophrenia when other antipsychotic medicines haven’t worked so well is still not completely understood. Clozapine has also been shown to reduce cravings to smoke and use other drugs. There is also evidence to suggest it protects against suicide for people with schizophrenia or schizoaffective disorders.

Clozapine and everyday life

You may experience some benefits in the first few weeks, but it could take several weeks before you start to feel any improvement.

Research has shown that about a third of people who start clozapine show an improvement in the first six weeks and this increases to two-thirds after one year.

Treatment with clozapine needs to start with a low dose that is gradually increased to a dose that is right for you over several weeks. The level of clozapine in your blood can be checked to see what dose is best for you.

Weight gain is a very common side effect of clozapine. It is more likely to cause weight gain compared with other antipsychotic medication. Young people naturally gain a little weight each year as they grow, but anything more than this should be monitored.

Your doctor will monitor your weight regularly when you’re taking clozapine. Talk to your doctor or pharmacist if you are concerned about your weight, or changes to your weight, while taking clozapine. They can review your medicine with you and look at any changes that could be made to help.

It’s very difficult to know how much weight you might gain, if any, as each person is affected differently. Reported weight gain tends to be more in the first year of treatment, especially the first few months.
Making sure you do enough exercise and eat a healthy diet (with vegetables and fibre) can help you to avoid putting on too much weight. Talk to your doctor, pharmacist and specialist healthcare team for advice on diet and lifestyle to help reduce the risk of weight gain.
Mental health conditions like schizophrenia and bipolar disorder can make being active and eating healthily more of a challenge. Talk to your doctor, pharmacist and specialist healthcare team for lifestyle advice and where to get support.

Clozapine can also affect how your body processes sugar, leading to high blood sugar levels. While this is uncommon, it can contribute to the development or worsening of diabetes, particularly in young people, and may be associated with weight gain.

Be alert for symptoms that suggest your body is struggling to process sugar, like excessive thirst, frequent urination, or persistent fatigue. If you experience these symptoms or have other concerns, schedule an appointment with your doctor.

If you already have diabetes, clozapine may impact your blood sugar levels. Discuss this with your doctor, monitor your blood glucose regularly, and you may need to adjust your diabetes medication accordingly.

Many people can produce more saliva than usual when they start to take clozapine, which can lead to drooling or dribbling. This usually happens early on in treatment and often gets better after the first few months, but can continue. If you’re affected, you should talk to your doctor or pharmacist about ways to manage it.

You may want to let your family and friends know you are taking clozapine so they can support you and help you look out for side effects.

For guidance on this, check out our page on getting support with your medication.

Clozapine can make you feel very sleepy, especially when you first start taking it or when the dose is increased. This side effect can improve over time.

If it doesn’t, or if you are worried and it is causing you distress, speak to your doctor or pharmacist.

Depending on the dose you are prescribed, it may be possible to take your dose in the evening or at bedtime to help minimise the sedation you get.

If you need to take clozapine twice a day, taking a smaller dose in the morning may help.

If you have been taking clozapine for more than a month and you continue to feel very sleepy during the day, you should go back to your doctor and discuss what changes could be made to help.

Alcohol

It may be possible to drink some alcohol in moderation while taking clozapine. But the two together might make you feel very sleepy and unsteady on your feet, especially when you first start taking the medication.

It’s best to stop drinking alcohol completely during the first few weeks of treatment, until you see how the medication affects you.

Drinking alcohol every day, or in large amounts, can make your symptoms worse and may mean you won’t get the maximum benefit from your medication.

Street drugs

Clozapine does not mix well with street drugs as antipsychotics block the effect of dopamine, meaning that the ‘high’ you experience may not be as potent as before from any drug. You may be tempted to increase your dose of the drug to make up for this, which could be very dangerous.

Mixing clozapine and benzodiazepines (which may also be mixed in other street drugs) can be very dangerous. You may have difficulty breathing and your heart may stop working properly.
Smoking cannabis can make any drowsiness experienced when taking clozapine worse.

Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis.
Clozapine is also likely to reduce the level of euphoria (happiness) you might normally experience when taking cocaine.

Clozapine and stimulant drugs such as amfetamines can affect the heart when taken together.

There are many other street drugs, but we don’t know what effect taking them with clozapine will have, so it’s best to be cautious. There is no regulation of street drugs or ‘legal highs’, so even if there are no known issues with the medication you take, the supply you receive might be mixed with other substances that could be dangerous.

Smoking

It is very important to tell your doctor or care team if you stop or start smoking while taking clozapine.

Smoking can have a huge effect on the level of clozapine in your body, and if you smoke it is likely that you will need a bigger dose of this medication.

If you stop smoking, or switch to vaping or nicotine replacement products, this is likely to significantly increase your clozapine levels and lead to increased side effects which could be very serious. It is important that you tell your doctor if you change your smoking habits or plan to give up. Your treatment will need to be reviewed and your dose reduced and monitored carefully.

Get more advice on drugs and alcohol.

Clozapine does not mix well with some other medicines, including herbal remedies. Some medicines may increase or decrease the metabolism of clozapine which could cause the level of clozapine to increase or reduce.
Combined hormonal contraceptives can increase the concentration of clozapine. Your doctor may need to review your dose if you start or stop this medicine.

Any medicines that can cause constipation should be used with care. This includes medicines like codeine for pain relief. Constipation can be a very serious side effect of clozapine.

The action of any medicine that causes sedation may be increased if combined with clozapine making you feel very tired and affecting your ability to do activities like driving a car or riding a bike safely.

Tell your doctor or pharmacist before you take clozapine if you are prescribed any other medication, to check that the combination is safe. This includes medicines you have bought at your pharmacy or local supermarket and medications that you put on your skin.

Look at the leaflet inside your medicine box for more information about other medicines that can interact with clozapine. With some medicines your doctor may need to adjust the dose of clozapine if you take them together. Ask a doctor or pharmacist for more information if you have any questions.

Clozapine levels can be changed by high doses of caffeine.

If you drink a lot of coffee, cola drinks or other high-caffeine drinks, it may increase your level of clozapine and this might be dangerous.

If you suddenly stop drinking caffeine, it could make your clozapine level fall.

Talk to your doctor before making any major changes to your diet or what you drink regularly.

Always let your pharmacist know if you have any food allergies or intolerances.

The tablets contain lactose so they may not be suitable for you if you have problems eating some sugars or dairy products.

The orodispersible tablets contain aspartame, which can be a problem for people with a condition called phenylketonuria.

There are multiple companies that manufacture clozapine, but you will usually be prescribed the same brand. If this does change, always check with the pharmacist if you are concerned about any of the ingredients in your medicine.

If you need to avoid animal products, please note that non-active ingredients used in the production of medicines may sometimes be of animal origin. Ask your pharmacist if you have any questions about the ingredients.

Further information about practical considerations for medicines if you need to avoid animal products can be found on the Vegan Society website.

You might feel sleepy or dizzy in the first few days or weeks after you start taking clozapine, or after an increase in dose.

It is recommended that you stop driving or riding a bike for the first few days or weeks after you start taking clozapine, until you know how it affects you.

Most people drive as normal while taking clozapine. If you are worried about this or have any concerns you would like to discuss, speak to your doctor or pharmacist.

You must tell The DVLA (Driver and Vehicle Licensing Agency) if you have bipolar disorder, schizophrenia, schizoaffective disorder or other mental health conditions that could affect your driving. You can be fined if you do not tell The DVLA about a medical condition that affects your driving and may be prosecuted if you are involved in an accident as a result.

Pregnancy

If you become pregnant while you are on clozapine, you should carry on taking it and make an appointment to see your doctor as soon as possible They can discuss the benefits and risks of continuing clozapine and help you to make a decision that is best for you and your baby. They may refer you to a specialist perinatal mental health team to support you with this decision.

If you are planning to get pregnant, it is recommended that you take folic acid while you are trying for a baby and during pregnancy. It is safe to take this together with clozapine.

Hormonal contraceptives may increase clozapine levels, so always discuss stopping these with your doctor so they can review your clozapine and adjust the dose if needed.

You can find out more information about taking clozapine during pregnancy at Bumps (Best Use of Medicines in Pregnancy).

Clozapine may slightly increase your chance of putting on extra weight and gestational (pregnancy-linked) diabetes during your pregnancy. Make sure your midwife is aware you are taking clozapine so they can advise on extra monitoring when appropriate.

During pregnancy it is standard practice for your midwife to assess your risk of blood clots. There are lots of things that can increase risk, and blood clots are also reported as a rare side effect of clozapine. If you have a higher risk of a blood clot, your doctor or midwife may advise the use of medicine to reduce this.

Remaining well is particularly important during pregnancy and while caring for a baby. If you have responded well to clozapine, continuing with this medicine in pregnancy may be the best option for you and your baby.

Post-natal

There are some symptoms that can occur in new born babies if clozapine is taken in the last three months of pregnancy. Look out for these and get help if they happen:

jerking or twitching of the muscles or a tremor
being jittery, irritable or constant crying
being too hot or cold
suckling/feeding difficulties
having stiff or floppy muscles, or overactive reflexes
being very sleepy or finding it difficult to sleep
breathing problems

These are usually mild and go away in a few days without treatment.

Breastfeeding

Clozapine is passed to the baby through breast milk in small amounts and there is a risk that this might cause side effects in your baby. Your doctor or pharmacist can discuss the risks and benefits with you and consider other feeding options if appropriate.

If your baby was premature or has health problems, then you will need to be extra careful about taking medicines while breastfeeding. It may not always be best to breastfeed if this is the case, but you should discuss this with your doctor or midwife.

If your medication makes you sleepy, do not to sleep with your baby in the same bed, and be cautious when handling your baby (especially if waking during the night for feeds).

Talk to your doctor or midwife about your feeding options. Make sure that your doctor, nurse, or health visitor checks your baby for any side effects.

While other medicines might be preferred during breastfeeding, if you are taking clozapine this is probably because other medicines have not worked well for you, so switching to an alternative might not be right for you. It is important for you to remain well while you are bonding with and looking after your baby, so it may be best to take clozapine for your mental health when breastfeeding.

Sex

Clozapine is unlikely to cause side effects that affect your sex life and is also less likely to do so than other antipsychotic medications.

There have been incidents of retrograde ejaculation reported as a side effect in men taking clozapine. This means that no semen, or only a small amount, is produced when you ejaculate, and your urine may also be cloudy when you next go to the toilet. You should still experience the feeling of orgasm, but it could be a problem if you are planning a family.

Clozapine can, in rare cases, cause a long-lasting painful erection (priapism). If it lasts longer than three hours, go to A&E.
Clozapine might cause other side effects which might affect your sex life indirectly if you experience them, including:

bedwetting
producing more saliva and dribbling/drooling

If you do experience these side effects, and this is a problem for you, make an appointment to discuss this with your doctor.

Untreated illness can have a negative effect on your sex life, so if clozapine helps you to recover, positive effects can include improving your desire, experience and enjoyment of intimate relationships again.

Fertility

From limited studies available, there is currently no evidence to suggest that clozapine has any direct effect on fertility.

Other antipsychotics are more likely to cause an increase in prolactin (a natural hormone in the body). If this is raised it may cause problems with your menstrual cycle and you could miss periods (or they could become irregular or stop altogether). This means it may be more difficult to get pregnant.

If this has been a problem for you when taking other antipsychotic medicines, you should find that your periods will return to a regular pattern when you switch to clozapine, as this medicine does not cause an increase in prolactin levels.

There have been incidents of retrograde ejaculation reported as a side effect in men taking clozapine. This means that semen travels backwards into the bladder instead of out through the urethra (the tube that urine passes through). This means that no semen, or only a small amount is produced when you ejaculate. Your urine may also be cloudy when you next go to the toilet. You should still experience the feeling of orgasm, but it could be a problem if you are planning a family.

Talk to your doctor about your clozapine if you are trying to get pregnant or planning a family.

Clozapine is not a banned substance in sport.

Most people play sports as normal while taking clozapine. However, taking clozapine may make you feel tired and dizzy and affect your eyesight. This could be dangerous in some sports so it might be best not to take part in them for the first few days or weeks until you know how it affects you.

If you are worried that taking clozapine might make doing the sports you enjoy more difficult, discuss this with your doctor.

Ideally it is best not to take clozapine for the first time just before your exams. Clozapine could make you feel very tired and dizzy, make you feel restless and affect your eyesight.

You should talk to your doctor about any future exams if you are starting clozapine. You might decide together to delay starting it until you have completed them.

If they are more than a week away, however, you might find that it is better to start clozapine to improve your motivation and ability to study.
Most people take exams as normal while taking clozapine. If you are worried that taking clozapine might make studying for or taking your exams harder, discuss this with your doctor.

Information and safety considerations

Your doctor will consider any other medical conditions or symptoms you have before recommending a medicine for you.

Your medicine will come with a ‘patient information leaflet’. It’s important that you read this information. Speak to your pharmacist if:

you’re not given a leaflet
you don’t understand the information
you need it in a different format or language
you’re concerned about something you’ve read

The information leaflet also includes a list of warnings and precautions to consider before you take the medicine. If you think that any of these apply to you and are concerned that your doctor is not already aware of them, check with your doctor or pharmacist before you start to take your medication (or as soon as possible if you are already taking it).

Uses, warnings, safety and side effects

Taking clozapine

If clozapine works for you, you may want to keep taking it for a long time.

For psychosis or schizophrenia, if you have had one episode of illness, then it’s best for you to keep taking clozapine for at least two years to reduce the chances of becoming ill again. If you have had more than one episode of illness, then a period of at least five years is recommended. However, if clozapine is helping to keep you well, you may want to continue for longer.

Your doctor should review your progress on this medication at least once a year. This will include a review of your dose and whether you’re experiencing any side effects.

You will get the best effect from clozapine if you take it regularly every day at the dose prescribed by your doctor.

You can take the tablets or liquid before or after food.

For the normal coated tablets, swallow them whole with a drink of water – if you chew them, they taste bitter.

To take an orodispersible tablet, put one on your tongue and let it dissolve there. You can also dissolve it in some water if you prefer.

If you take the oral liquid, make sure you shake the bottle well before each dose. If not, the medicine may not be mixed up properly and you may get the wrong dose which could be dangerous.
It is important that you attend your appointments for regular blood tests. If the blood test result is not available, the pharmacy cannot dispense your medicine.

If you are planning a holiday, talk to your doctor and care team as soon as possible. They can support you to make special arrangements for blood tests and to make sure you will have enough medication for your trip.

If you forget to take a dose, you should take it as soon as possible, unless it is less than four hours until your next dose.
If you forget by the time your next dose is due, just take your next dose. Do not try and catch up by taking a double dose.

If you miss more than two days of clozapine (48 hours), you need to start again at a low dose. If this happens, speak to your doctor or care team. If you start again at your old dose, you may get some serious side effects which could be dangerous, such as a drop in blood pressure leading to dizziness, unpleasant heart sensations and feeling very tired. Your doctor will advise you to restart your clozapine with a lower dose and gradually increase the dose back to the treatment dose you were prescribed.

If you forget to take your tablets for a while, you may start getting your old symptoms back or get withdrawal symptoms. You should talk to your doctor if this happens.

Regularly forgetting to take your medication can increase the risk of you becoming ill again and may mean that your symptoms could be worse if you become unwell again.

If you are struggling to remember to take your medication regularly as prescribed by your doctor, speak to your pharmacist and doctor for advice to help you.

Make sure you take enough medication with you if you are going away.

Ideally clozapine should be stopped gradually over a month or more, although this is not always possible. In some situations, it may be necessary to stop clozapine suddenly. If you get a ‘red’ blood result after your routine blood test, it means you need to stop clozapine urgently. Your specialist doctor will give you advice and support with this, including any withdrawal symptoms you might experience.

Where stopping clozapine can be planned, discuss this with your doctor. If you have important events coming up or going through a period of life which is very demanding, it might not be the best time to stop your medication. Planning and support are important to stopping your medication successfully.

Clozapine is not addictive, but if stopped suddenly it can cause discontinuation or withdrawal symptoms and increase the risk of becoming unwell again.

Once you start taking an antipsychotic medicine, the brain adjusts to having a new level of dopamine and other neurotransmitters around. If you stop taking it suddenly, the balance starts to change. It takes time for your body to readjust, and you may be more sensitive to the levels of dopamine that are in your body.

Some of the withdrawal symptoms may be like symptoms you had when you were unwell, so understandably, you might feel anxious or upset that your illness could be returning.

Withdrawal symptoms usually start within a few days of stopping (or sometimes reducing) your medication. A wide range of symptoms have been reported and are listed below. You may experience a few or a range of these:

difficulty getting to sleep or disturbed sleep
low mood, feeling anxious or agitated or restless
dizziness or light-headedness
headaches
reduced concentration or feeling confused
feeling sick or being sick
diarrhoea
flu-like symptoms
tense or jerky muscles and slow movements
uncontrollable movement of face or body
hallucinations or intrusive thoughts

You can stop taking clozapine safely with your doctor’s help. They will work with you to reduce your dose gradually rather than stopping suddenly. The speed at which you reduce depends on how unwell you were and how long you have been on clozapine.

Warnings and safety

If you have taken more than the dose prescribed by your doctor, contact NHS 111 immediately to ask for advice, or ask a family member or friend to do this for you. This is important even if you don’t feel any different.

NHS 111 can give you advice and direct you to the best place to get more help if you need it.

If you have taken too much medication on purpose, or if after taking this you quickly feel unwell, call 999 or get someone to take you to A&E straight away. This includes any of the following signs:

drowsiness and lack of energy
reduced levels of consciousness
agitation and confusion
hallucinations
unclear speech
unusual movements, stiff limbs, trembling hands
seizures or fits
fast or irregular heartbeat and difficulty breathing

If you need to go to A&E, do not travel alone or drive yourself there. Get your parent, family member or friend to go with you to support you and keep you safe on the way. If someone is not able to drive you there, call for an ambulance. Take your medication with you and tell doctors how much you have taken.

Serious side effects

Clozapine can cause serious side effects including allergic reactions.

Stop taking clozapine and go to a hospital straight away if you get any of the following symptoms:

difficulty breathing
an allergic reaction or allergy (including symptoms such as swelling of your face, eyelids, lips, tongue or throat so that you cannot swallow or breathe, or really bad itching of the skin with raised lumps)
sudden high fever, muscle stiffness, sweating or drowsiness or sleepiness (these symptoms could be caused by neuroleptic malignant syndrome)
stomach pain, cramping, swollen abdomen, being sick, constipation (finding it difficult to poo) and not able to pass wind (these may mean that your bowel is blocked)
swelling, pain and redness in the leg, arm or tummy (this could be a blood clot)
crushing chest pain, chest tightness, pressure or squeezing (Chest pain may move from your chest to the left arm, jaw, neck and stomach. You may also get shortness of breath, sweating, weakness, light-headedness, feeling or being sick and palpitations. These might be symptoms of a heart attack.)
seizures or fits
a painful erection (priapism) that lasts more than three hours

Get your parent, family member or friend to take you or go with you to support you and keep you safe on the way. If someone is not able to drive you there, call for an ambulance. Take your medication with you.

Contact your doctor immediately (before taking the next dose of clozapine) but don't stop taking clozapine, if you get any of the following symptoms:

have signs of a cold, fever, flu-like symptoms, sore throat or any other infection (you will have to have an urgent blood test to check if your symptoms are related to your medicine)
have a fast and uneven heartbeat, even when you are resting, palpitations, breathing problems, chest pain or unexplained tiredness
find it difficult to poo for more than a few days (you are very constipated)
develop new symptoms which include needing to drink a lot, needing to pee a lot, feeling weak or feeling hungry despite having an increased appetite (these might indicate your body is not processing sugar very well)
swelling, pain, and redness in the leg, which may be from a blood clot (if you have symptoms of breathlessness or chest pain too go straight to A&E)

It is very important to tell your doctor if your bowel habits change (the number of times you do a poo). If there is any reduction in the number of times you usually go to the loo to poo each week, or if you poo less than three times a week, you must let your doctor know immediately. Constipation is a common side effect of clozapine (higher than other antipsychotic medicines) and if not treated it can be very serious. Checking that your bowels are working normally is just as important as having your blood test taken regularly.

If you are unable to contact your doctor, call NHS 111 for urgent advice.

Side effects and your health

Side effects are more common when you first start taking clozapine. Many go away as you continue your medicine. If they don’t get better, or if you are worried by them and they are causing you distress, speak to your doctor, specialist team or pharmacist about them.

Very common side effects of clozapine (affecting more than one in ten people) include:

feeling sleepy, tired, weak or exhausted
feeling dizzy or faint, especially when getting up from a lying or sitting position (this usually happens at the start of your treatment and will normally pass on its own)
weight gain
constipation (this can be a very serious side effect and must be treated quickly)
increased saliva

It is very important to tell your doctor if your bowel habits change (the number of times you do a poo). If there is any reduction in the number of times you usually do a poo each week or you do a poo less than three times a week, you must let your doctor know immediately.

Common side effects of clozapine (affecting up to one in ten people) include:

blurred vision
headache
abnormal movements, muscle stiffness, trembling and restlessness
dry mouth
feeling or being sick
urinary incontinence (weeing when you don’t want to) – this may be overnight

Up to one in ten people start to wet the bed when they begin taking clozapine. If this happens to you, restrict the amount that you drink before bedtime and speak to your doctor about other possible solutions, including medications that can stop bedwetting.

There are other side effects that you can get when taking this medicine. We have only included the most common ones here.

This list of side effects can look scary. You may not experience any of them, but it’s important to be aware of them so you know what to do if they do happen.

Unless your side effects are very severe or distressing, try to continue taking your medication until you can talk to your doctor. Your doctor can make changes to your medication to help if needed.

Clozapine use has been linked to an increased risk of developing diabetes among some young people. Symptoms include:

putting on weight
needing to wee a lot
needing to drink a lot
feeling weak
always feeling hungry

Speak to your doctor if you develop these symptoms.

If you already have diabetes, you may need to increase the amount of medication you take for this alongside taking clozapine.

Clozapine can cause a drop in your white blood cells (which fight infection). This might not cause any symptoms until you get an infection. This is why it is important to have regular blood tests while you are taking clozapine.

You should have your weight, blood sugar, blood fats, prolactin level, blood pressure and pulse measured before you start clozapine and regularly during early treatment, then at least every six months (if you are under 18) or once a year (if you are over 18) after that.
A blood test will be required to check your blood sugar, blood fats and prolactin level.

Your doctor might also check your heart with an electrocardiogram (ECG) and your liver function. A blood test is required for this.
They might also check your height and development.

It is very important to go for these checks when you are asked to do so. If you are worried or anxious about the monitoring, talk to your doctor, care team or practice nurse about this for advice and support.
You could take some of these measurements at home (e.g. weight ) and keep a record of the results to share with your doctor when they review your treatment.

When you first start clozapine your pulse, blood pressure and temperature will be monitored more closely to check for possible side effects from the clozapine and make sure these are managed quickly if they do occur.

You will also need regular blood tests all the time you are on clozapine. These are every week when you first start clozapine, every fortnight after 18 weeks of treatment and reduce to once every four weeks after a year.

These blood tests check on the health of your blood cells, especially your white blood cells, which are important for fighting off infections.

An additional blood test is available to measure the level of clozapine in your body. This helps your doctor to check that the dose of medicine prescribed is right for you. This doesn’t need to be monitored regularly, but will help your doctor to review your treatment and is important if there are any changes in your condition or life style (for example if you start getting more side effects or if you stop smoking).