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Your guide to medication Olanzapine

Olanzapine is an atypical antipsychotic used to treat bipolar disorder, schizophrenia and psychosis.

Medication name: Olanzapine ("oh-LAN-za-peen")
Brand name: Zyprexa¬ģ ("zi-PREX-a")
Medication type: Atypical antipsychotic (AKA second-generation antipsychotic)


Ways to take olanzapine
Tablets: 2.5mg, 5mg, 7.5mg, 10mg, 15mg, and 20mg strengths
Orodispersible (‚Äėmelt in your mouth‚Äô) tablets: 5mg, 10mg, 15mg and 20mg strengths (these may be called Zyprexa Velotabs¬ģ)
Injections: 210mg, 300mg or 405mg in one injection (this may be called Zypadhera¬ģ)

What can it be used for?
If you are 18 or over, the doctor can prescribe olanzapine for you as a licensed medicine for mania, schizophrenia and bipolar disorder.

There is less research about its use and effectiveness in people under 18. Even so, specialists might prescribe it ‚Äėoff-label‚Äô if they believe it is the best medicine for you.

Read our guide to psychosis

About olanzapine

How olanzapine works

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.

The main effect that olanzapine has is to block some dopamine receptors in the brain, correcting the overactivity of dopamine.

Olanzapine also has effects on other neurotransmitters in the brain such as serotonin (5-HT), which may also contribute to its beneficial effects.

Olanzapine and everyday life

Frequently asked questions

It can take four to six weeks for olanzapine to show its full effects, but some studies show a good effect for some people within the first week of taking it.

You should stay in touch with your doctor to see how it goes over the first few weeks. They might do some tests to check your symptoms.

If you have had no good effects after two to three weeks, your doctor may increase the dose or change the medicine

Your doctor might start you on a low dose and then increase it slowly over two to four weeks to your full dose.

If you are starting on the long-acting injection (Zypadhera¬ģ), it can take a few days for the first injection to start working.

If you switch from olanzapine tablets to the injection, you may need to continue taking your tablets for the first few weeks after your first injection, as the injection takes a few weeks to kick in.

A common side effect of olanzapine is weight gain. You need to have your weight checked regularly while you are taking it.

Talk to your doctor about this if it worries you.

It is thought that one of the reasons olanzapine causes weight gain is that it increases appetite.

Making sure to do enough exercise and eat a healthy diet (with vegetables and fibre) can help you to avoid putting on too much weight.

You may want to let your family and friends know you are taking olanzapine 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.

Alcohol

You can continue to drink some alcohol while taking olanzapine, but having the two together might make you very sleepy or make you fall over.

If you drink a lot of alcohol, these effects will be much more serious.

Alcohol can also make the symptoms of your condition worse.

During the first few days, it might be best to stop drinking alcohol until you see how the medicine affects you.

If you want to drink alcohol, remember that you might be sleepy and make sure you can get home safely.

Street drugs

Antipsychotics block the effect of dopamine, so the 'high' you get from drugs that work by increasing levels of dopamine may not be as 'high' as before. You may be tempted to increase your dose of the drug to make up for it, but this could be dangerous.

Cannabis can make drowsiness worse with olanzapine. It can also make your symptoms worse.

Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis. For more information, have a look at our drugs and alcohol page.

Methadone can make drowsiness worse with olanzapine and potentially cause dangerous problems with the rhythm of your heart.

All antipsychotics can reduce the stimulant effects of cocaine.

Smoking

If you start or stop smoking while you are taking olanzapine, you may have to change your dose.

Cigarette smoke affects the amount of olanzapine in your body.

If you smoke, you may need a higher dose of olanzapine than someone who does not smoke.

Tell your doctor if you smoke, so that you get the right dose for you.

If you stop smoking, the level of olanzapine in the body rises, and you might need to reduce your dose of olanzapine slowly over one week.

If you (re)start smoking, you may need to increase it again

Go to your doctor for advice if you stop or start smoking.

Olanzapine does not mix well with some other medicines and drugs. 

Tell your doctor before you take olanzapine if you are taking any other medicines.

Tell the pharmacist you are taking olanzapine if you buy medicines over the counter (including things you put on your skin) for common illnesses.

There are many companies making olanzapine tablets and the orodispersible ones. The non-active ingredients are likely to vary so if you have intolerances to certain sugars (e.g. lactose) or certain sweeteners (such as aspartame) then ask your pharmacist to check for you.

If you need to avoid animal products such as gelatin, please note that this is often found in capsules but also in some tablet formulations. Ask your pharmacist if you have any questions about the ingredients.

Do not drive a car or ride a bike just after you start taking olanzapine.

Olanzapine may make you feel tired or dizzy when you start taking it.

This could affect you if you drive a car, ride a bike, or do anything else that needs a lot of focus. It might be best to stop doing these things for the first few days, until you know how it affects you.

Do not worry - most people drive as normal while taking olanzapine.

Pregnancy

Olanzapine is not seen as high-risk during pregnancy and, if regular medicine is keeping you well, then changing your medication may be the greater risk. A study of over 800 mums who took olanzapine during pregnancy suggested no increased risk of malformations, miscarriage or premature birth.

Olanzapine is an antipsychotic medicine. Taking antipsychotics can cause folate levels to become low, which is not good for a healthy pregnancy. Taking 5mg folic acid a day before and during pregnancy can reduce the risk of your baby having spine problems.

Olanzapine may slightly increase your chance of getting high blood pressure linked to pregnancy (pre-eclampsia), putting on extra weight and gestational (pregnancy-linked) diabetes.

Expect your blood sugar levels, weight and blood pressure to be more closely checked from month four onwards of your pregnancy if you are on olanzapine.

A blood-thinning agent may also be advised. This is because sometimes there can be a risk of getting a blood clot in the leg during pregnancy.

Post-natal

Taking olanzapine close to delivery may lead to some discontinuation (withdrawal) effects in your baby. These may include being irritable, crying or problems feeding and sleeping. These are usually mild and go away in a few days without treatment.

Make sure that your doctor, nurse, or health visitor checks your baby for any side effects. These can include:

  • being extra sleepy
  • having colic
  • feeding problems
  • being floppy
  • poor weight gain

Breastfeeding

Olanzapine gets into breast milk, but only in small amounts (around 1%).

Breastfeeding may help with any discontinuation (withdrawal) effects.

There is a risk of the baby becoming a little sleepier if breastfed when the mother is taking olanzapine.

You should talk to the doctor if you are taking olanzapine and thinking of breastfeeding after you give birth to your baby.

If your baby was premature or has health problems, then you will need to be extra careful about taking medicines while breastfeeding. Discuss this with your doctor.

Remember that it is important for you to stay well while you are bonding with and looking after your baby. This means that you may need to take olanzapine or another medicine for your mental health when breastfeeding.

Talk to your doctor or midwife about your feeding options.

Sex

Olanzapine can have side effects that might affect your sex life, but they should not last for long. These include:

  • drop in libido (how much you want to have sex)
  • difficulty getting an erection
  • (very occasionally) breast growth and, in very rare instances, some milk flow, regardless of gender

Some of these effects should pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what other medicines you could try.

The good effects of olanzapine may have a positive impact on your sex life as your symptoms settle, and you can concentrate on your relationships.

Fertility

Olanzapine may increase the level of a hormone called prolactin in the body for a short time when you start taking it, but not to a very high level. If prolactin levels do rise for a short time after starting olanzapine, this may affect fertility, regardless of gender. However, this is not a common problem for people who take olanzapine.

If you are trying for a baby, or become pregnant while taking olanzapine, you should speak to your doctor as soon as possible.

Olanzapine is not a banned substance in sport.

It can, however, make you feel tired or dizzy, so this might affect your performance in sports that need a lot of focus. You need to see how it affects you.

Do not worry - most people play sports as normal while taking olanzapine.

Try not to take olanzapine for the first time just before your exams.

Olanzapine can make you feel tired and dizzy, and can affect your memory.

You should talk to your doctor about any future exams if you are starting olanzapine.

You might decide together to delay starting it until you have done them.

You might find that it is better, however, to start olanzapine to improve your symptoms and your ability to study and do the exams.

You could take your olanzapine at night (if you do not do that already) to see if that is better for you.

Do not worry - most people take exams as normal while taking olanzapine.

Uses, warnings, safety and side effects

Taking olanzapine

How long will I need to take olanzapine for?

Many people take olanzapine for a few years.

How long you need to take it will depend on what condition you are taking it for.

You and your doctor should talk about how long you need to take olanzapine before you start your treatment.

If you stop the olanzapine, you will go back for checks to see that your old symptoms do not come back.

For psychosis or schizophrenia, if you have had one episode of illness, then it is best for you to keep taking olanzapine 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.

If you are taking olanzapine to treat bipolar mania or bipolar depression, then you will need to discuss long-term medicines for your bipolar disorder with your doctor. This is to help stop the illness coming back.

For bipolar disorder, it is important to remain on medicines in the long term because every time you become ill, there is more chance of you becoming ill again. Olanzapine can be used as a long-term medicine, but there are other choices and lithium is still thought to be the best long-term medicine for bipolar disorder. You should discuss your options with your doctor.

For schizoaffective disorder, it is probably best to keep taking the olanzapine for several years to reduce the chances of the illness coming back. We know less about schizoaffective disorder, but it has some similarities to bipolar disorder and some similarities to schizophrenia.

Depression is usually treated with an antidepressant medicine, and olanzapine is sometimes added to an antidepressant for more severe depression. For people with severe depression, it is best to continue the antidepressant medicine for at least two years to stop the illness from coming back. The doctor is likely to recommend continuing olanzapine for the same length of time.

You should only take olanzapine as agreed with your doctor

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

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

You may start with a low dose that increases slowly to your regular dose over the next few days.

You will usually take your dose once a day.

It is usually recommended to take olanzapine at bedtime because it can cause sleepiness as a side effect.

However, it is important to choose a time of day to take it that you can easily remember, which could be bedtime, a mealtime, or when you brush your teeth.

You can take it before or after food.

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

Put orodispersible tablets (melts) on your tongue and let them dissolve there. You can also dissolve these in a glass of water, orange juice, apple juice or milk and then drink it all down.

A doctor or nurse can give you an injection in your bottom that provides a long-lasting dose of olanzapine, lasting for two or four weeks. You may need to take tablets alongside the injection, especially while the dose builds up. Every time you have the injection, you will be asked to wait at the centre for at least three hours so that they can check that the injection is not giving you too much olanzapine in one go. The good thing about a long-acting injection is that you don’t have to remember to take so many tablets every day. It is slowly working in your body all the time between injections.

What if I miss a dose?

If you remember later during the day, take it as soon as possible.

If you forget to take it by bedtime, just start again on the next day. Do not take a double dose.

If it is less than 12 hours before your next dose of olanzapine, then do not take the missed dose because taking the doses too close together could cause more side effects.

If you miss your appointment for your injection, contact your doctor or nurse straight away to make another appointment.

It is very important to have the injection every two or four weeks.

What will happen if I forget to take my olanzapine?

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

Stopping the use of olanzapine

Once you start taking an antipsychotic, the brain adjusts to having a new level of dopamine around. If you stop taking the antipsychotic all at once, the balance starts to change again. You could get your old symptoms back.

Stopping this medicine quickly, or reducing the dose too much at once, may cause your old symptoms to come back, or cause you some withdrawal effects.

You can stop taking it safely with your doctor’s help.

People usually take olanzapine for a long time, to keep their symptoms away.

You may get your old symptoms back if you stop olanzapine for a while. You can also get withdrawal effects, including:

  • difficulty sleeping
  • feeling or being sick

It is better to agree stopping with a doctor who will reduce your dose gradually. This is likely to take a few weeks.

You will probably go for checks with your doctor after you stop olanzapine to check that you still feel better. 

Warnings and safety

Safety headlines

If you have taken more olanzapine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different.

Olanzapine can sometimes cause serious side effects. Tell your doctor immediately if you experience unusual movements (mainly of the face or tongue).

Go to hospital immediately if you think you may have developed a blood clot (symptoms are usually swelling, pain and redness in the leg) - a clot may travel through blood vessels to the lungs causing chest pain and difficulty breathing.

Also go to hospital and tell the doctor you are taking olanzapine if you develop a combination of fever, faster breathing, sweating, muscle stiffness or drowsiness.

Stopping olanzapine suddenly can cause withdrawal effects and stopping it too early could cause your illness to come back. See your doctor if you want to stop taking olanzapine because it is better to come off it gradually.

You might feel sleepy or dizzy in the first few days after taking olanzapine. Do not drive a car, ride a bike or operate machines until you see how this affects you.

If you are pregnant, or thinking of becoming pregnant, please read the pregnancy section (under the 'Side Effects' tab) because olanzapine may affect the developing baby.

When to go to the hospital

If you have taken more olanzapine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different. Go to A&E. Take your medicine with you to show to the doctors. Tell them how much you have taken. Get a friend to go with you, if you can, just in case you feel ill on the way.

You might get any of the following signs:

  • rapid beating of the heart
  • agitation/aggressiveness
  • problems with speech
  • unusual movements (especially of the face or tongue)
  • reduced level of consciousness or coma
  • confusion
  • seizures (fits)
  • a combination of fever, faster breathing, sweating, muscle stiffness and drowsiness or sleepiness, slower breathing, aspiration (breathing in vomit, mucus, or blood), high blood pressure or low blood pressure, and unusual rhythms of the heart

Go to a doctor or hospital straight away if you get any of the following symptoms while taking olanzapine:

  • allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps)
  • glaucoma (increased pressure inside your eyes, which can damage your vision) ‚Äď symptoms include eye pain, red eyes, headache, tenderness around the eyes, blurred vision, and seeing¬†rings around lights
  • swelling, pain, and redness in the leg, which may be from a blood clot. Such a clot could travel through blood vessels to the lungs causing chest pain and breathing difficulties
  • any combination of fever, faster breathing, sweating, muscle stiffness and drowsiness or sleepiness
  • repetitive, regular movements of the tongue, mouth and face that you‚Äôre not able to control. This condition is called ‚Äėtardive dyskinesia‚Äô and is extremely rare but can be very serious. It may not stop even when you stop taking the medication. If you notice it early and act with your doctor, the problem should not get worse

When to see your doctor

You need to talk to your doctor or pharmacist before starting treatment with olanzapine if any of the following apply to you:

  • stroke or ‚Äúmini‚ÄĚ stroke (temporary symptoms of stroke)
  • Parkinson‚Äôs disease
  • prostate problems
  • a blocked intestine (paralytic ileus)
  • liver or kidney disease
  • any blood disorders
  • heart disease
  • diabetes
  • seizures (fits)
  • glaucoma
  • respiratory (lung) diseases

Monitoring

You should have your weight, blood sugar, blood fats, blood pressure and pulse measured regularly during early treatment, then at least every six months to a year after that, depending on your age.

You should also have your blood sugar tested when you start, after one month, and then every four to six months after that.

The doctor might also check your heart with an electrocardiogram (ECG) and check your blood pressure.

They might also check your height and development. If you have periods, they may also check whether they are regular.

It is very important to go for these checks when you are asked to do so.

Side effects

Side effects

Please do not be worried by the side effects listed on this page. Some people take olanzapine without any side effects or with only a few mild side effects. Some side effects wear off after a few days or weeks.

If you think you might be getting a side effect from olanzapine, then you should discuss this with your doctor, nurse, or pharmacist.

Do not stop taking the tablets until you talk to your doctor, or you may get withdrawal symptoms as well.

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

  • weight gain
  • increases in the levels of prolactin in the blood (seen only in blood tests)
  • feeling dizzy or faint with a slow heart rate, 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 (speak to your doctor if it doesn't)

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

  • changes in the level of some blood cells, chemicals, circulating fats and, in early treatment, temporary increases in liver enzymes (seen only in blood tests)
  • increased appetite
  • tremor, muscle stiffness or unusual muscle movements
  • dry mouth
  • loss of strength or extreme tiredness
  • water retention leading to swelling of the hands, ankles or feet
  • joint pain
  • sexual problems such as feeling less like having sex less and problems getting an erection

Olanzapine 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
  • raised blood sugar levels

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

Taking olanzapine

How long will I need to take olanzapine for?

Many people take olanzapine for a few years.

How long you need to take it will depend on what condition you are taking it for.

You and your doctor should talk about how long you need to take olanzapine before you start your treatment.

If you stop the olanzapine, you will go back for checks to see that your old symptoms do not come back.

For psychosis or schizophrenia, if you have had one episode of illness, then it is best for you to keep taking olanzapine 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.

If you are taking olanzapine to treat bipolar mania or bipolar depression, then you will need to discuss long-term medicines for your bipolar disorder with your doctor. This is to help stop the illness coming back.

For bipolar disorder, it is important to remain on medicines in the long term because every time you become ill, there is more chance of you becoming ill again. Olanzapine can be used as a long-term medicine, but there are other choices and lithium is still thought to be the best long-term medicine for bipolar disorder. You should discuss your options with your doctor.

For schizoaffective disorder, it is probably best to keep taking the olanzapine for several years to reduce the chances of the illness coming back. We know less about schizoaffective disorder, but it has some similarities to bipolar disorder and some similarities to schizophrenia.

Depression is usually treated with an antidepressant medicine, and olanzapine is sometimes added to an antidepressant for more severe depression. For people with severe depression, it is best to continue the antidepressant medicine for at least two years to stop the illness from coming back. The doctor is likely to recommend continuing olanzapine for the same length of time.

You should only take olanzapine as agreed with your doctor

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

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

You may start with a low dose that increases slowly to your regular dose over the next few days.

You will usually take your dose once a day.

It is usually recommended to take olanzapine at bedtime because it can cause sleepiness as a side effect.

However, it is important to choose a time of day to take it that you can easily remember, which could be bedtime, a mealtime, or when you brush your teeth.

You can take it before or after food.

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

Put orodispersible tablets (melts) on your tongue and let them dissolve there. You can also dissolve these in a glass of water, orange juice, apple juice or milk and then drink it all down.

A doctor or nurse can give you an injection in your bottom that provides a long-lasting dose of olanzapine, lasting for two or four weeks. You may need to take tablets alongside the injection, especially while the dose builds up. Every time you have the injection, you will be asked to wait at the centre for at least three hours so that they can check that the injection is not giving you too much olanzapine in one go. The good thing about a long-acting injection is that you don’t have to remember to take so many tablets every day. It is slowly working in your body all the time between injections.

What if I miss a dose?

If you remember later during the day, take it as soon as possible.

If you forget to take it by bedtime, just start again on the next day. Do not take a double dose.

If it is less than 12 hours before your next dose of olanzapine, then do not take the missed dose because taking the doses too close together could cause more side effects.

If you miss your appointment for your injection, contact your doctor or nurse straight away to make another appointment.

It is very important to have the injection every two or four weeks.

What will happen if I forget to take my olanzapine?

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

Stopping the use of olanzapine

Once you start taking an antipsychotic, the brain adjusts to having a new level of dopamine around. If you stop taking the antipsychotic all at once, the balance starts to change again. You could get your old symptoms back.

Stopping this medicine quickly, or reducing the dose too much at once, may cause your old symptoms to come back, or cause you some withdrawal effects.

You can stop taking it safely with your doctor’s help.

People usually take olanzapine for a long time, to keep their symptoms away.

You may get your old symptoms back if you stop olanzapine for a while. You can also get withdrawal effects, including:

  • difficulty sleeping
  • feeling or being sick

It is better to agree stopping with a doctor who will reduce your dose gradually. This is likely to take a few weeks.

You will probably go for checks with your doctor after you stop olanzapine to check that you still feel better. 

Warnings and safety

Safety headlines

If you have taken more olanzapine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different.

Olanzapine can sometimes cause serious side effects. Tell your doctor immediately if you experience unusual movements (mainly of the face or tongue).

Go to hospital immediately if you think you may have developed a blood clot (symptoms are usually swelling, pain and redness in the leg) - a clot may travel through blood vessels to the lungs causing chest pain and difficulty breathing.

Also go to hospital and tell the doctor you are taking olanzapine if you develop a combination of fever, faster breathing, sweating, muscle stiffness or drowsiness.

Stopping olanzapine suddenly can cause withdrawal effects and stopping it too early could cause your illness to come back. See your doctor if you want to stop taking olanzapine because it is better to come off it gradually.

You might feel sleepy or dizzy in the first few days after taking olanzapine. Do not drive a car, ride a bike or operate machines until you see how this affects you.

If you are pregnant, or thinking of becoming pregnant, please read the pregnancy section (under the 'Side Effects' tab) because olanzapine may affect the developing baby.

When to go to the hospital

If you have taken more olanzapine than the dosage recommended by the doctor who prescribed it to you, you must get medical help immediately ‚Ästeven if you do not feel any different. Go to A&E. Take your medicine with you to show to the doctors. Tell them how much you have taken. Get a friend to go with you, if you can, just in case you feel ill on the way.

You might get any of the following signs:

  • rapid beating of the heart
  • agitation/aggressiveness
  • problems with speech
  • unusual movements (especially of the face or tongue)
  • reduced level of consciousness or coma
  • confusion
  • seizures (fits)
  • a combination of fever, faster breathing, sweating, muscle stiffness and drowsiness or sleepiness, slower breathing, aspiration (breathing in vomit, mucus, or blood), high blood pressure or low blood pressure, and unusual rhythms of the heart

Go to a doctor or hospital straight away if you get any of the following symptoms while taking olanzapine:

  • allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps)
  • glaucoma (increased pressure inside your eyes, which can damage your vision) ‚Äď symptoms include eye pain, red eyes, headache, tenderness around the eyes, blurred vision, and seeing¬†rings around lights
  • swelling, pain, and redness in the leg, which may be from a blood clot. Such a clot could travel through blood vessels to the lungs causing chest pain and breathing difficulties
  • any combination of fever, faster breathing, sweating, muscle stiffness and drowsiness or sleepiness
  • repetitive, regular movements of the tongue, mouth and face that you‚Äôre not able to control. This condition is called ‚Äėtardive dyskinesia‚Äô and is extremely rare but can be very serious. It may not stop even when you stop taking the medication. If you notice it early and act with your doctor, the problem should not get worse

When to see your doctor

You need to talk to your doctor or pharmacist before starting treatment with olanzapine if any of the following apply to you:

  • stroke or ‚Äúmini‚ÄĚ stroke (temporary symptoms of stroke)
  • Parkinson‚Äôs disease
  • prostate problems
  • a blocked intestine (paralytic ileus)
  • liver or kidney disease
  • any blood disorders
  • heart disease
  • diabetes
  • seizures (fits)
  • glaucoma
  • respiratory (lung) diseases

Monitoring

You should have your weight, blood sugar, blood fats, blood pressure and pulse measured regularly during early treatment, then at least every six months to a year after that, depending on your age.

You should also have your blood sugar tested when you start, after one month, and then every four to six months after that.

The doctor might also check your heart with an electrocardiogram (ECG) and check your blood pressure.

They might also check your height and development. If you have periods, they may also check whether they are regular.

It is very important to go for these checks when you are asked to do so.

Side effects

Side effects

Please do not be worried by the side effects listed on this page. Some people take olanzapine without any side effects or with only a few mild side effects. Some side effects wear off after a few days or weeks.

If you think you might be getting a side effect from olanzapine, then you should discuss this with your doctor, nurse, or pharmacist.

Do not stop taking the tablets until you talk to your doctor, or you may get withdrawal symptoms as well.

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

  • weight gain
  • increases in the levels of prolactin in the blood (seen only in blood tests)
  • feeling dizzy or faint with a slow heart rate, 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 (speak to your doctor if it doesn't)

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

  • changes in the level of some blood cells, chemicals, circulating fats and, in early treatment, temporary increases in liver enzymes (seen only in blood tests)
  • increased appetite
  • tremor, muscle stiffness or unusual muscle movements
  • dry mouth
  • loss of strength or extreme tiredness
  • water retention leading to swelling of the hands, ankles or feet
  • joint pain
  • sexual problems such as feeling less like having sex less and problems getting an erection

Olanzapine 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
  • raised blood sugar levels

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

About this information

The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.

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