What is alemtuzumab?

Alemtuzumab belongs to a group of targeted therapy drugs called monoclonal antibodies. It is best to read our information about alemtuzumab with our general information about targeted therapy drugs and the type of cancer you have. 

Your doctor will talk to you about this treatment and its possible side effects before you agree (consent) to have treatment.

More information about this treatment

This information is correct at time of publishing. But sometimes the types of cancer this treatment is used for, or treatment side effects, may change between revision dates.

You can talk to your cancer team if you want more detailed information about this treatment. Or visit the electronic Medicines Compendium (eMC) website, which has patient information leaflets (PIL) for individual drugs.

How alemtuzumab is given

If it is suitable for you, your doctor can apply for alemtuzumab through a patient access scheme. Or it may be available as part of a clinical trial. Your blood cancer doctor (haematologist) can tell you if it is appropriate for you. 

You will be given alemtuzumab at a day unit, during a stay in hospital or as an outpatient. Alemtuzumab can be given on its own or with other cancer drugs. 

During treatment, you usually see a:

  • haematologist
  • cancer nurse or specialist nurse
  • specialist pharmacist. 

This is who we mean when we mention doctor, nurse or pharmacist in this information.

Before or on the day of each treatment, a nurse or person trained to take blood (phlebotomist) will take a blood sample from you. This is to check that it is safe for you to have treatment. 

You will speak to a doctor, nurse or pharmacist before you have treatment. They will ask how you have been feeling. If your blood results are okay, the pharmacy team will prepare your targeted therapy.

The drug can be given as an injection under the skin (subcutaneous) or as a drip into a vein (intravenous infusion). 

If you are having treatment as an outpatient, you may need to stay in the unit for a few hours after the treatment. This is to make sure you do not have any signs of a reaction.

If you have subcutaneous injections and do not have problems with reactions, it may be possible to have your injections at home. A district or community nurse can give these injections. You will still come to the hospital regularly for check-ups and blood tests.

Your course of treatment

The first time you have alemtuzumab, you have a low dose. This reduces the risk of you having a reaction to the drug. The doctor increases the dose over the next few days until you are on the recommended dose. This usually takes from 3 to 7 days. After this, you have alemtuzumab 3 times a week, usually on a Monday, Wednesday and Friday.

Sometimes, alemtuzumab is given in combination with other drugs.

Your doctor or nurses will explain more about how alemtuzumab is given. They can also tell you how long your treatment will last.

About side effects

We explain the most common side effects of this treatment here. We also include some that are less common. 

You may get some of the side effects we mention, but you are unlikely to get all of them. And you may have some side effects, including rarer ones, that we have not listed here. 

Other cancer treatments may cause different side effects. If you are also having other cancer treatment, you may have other side effects.

Always tell your doctor, nurse or pharmacist about any side effects you have. They can give you: 

  • drugs to help control some side effects 
  • advice about managing side effects. 

It is important to take any drugs exactly as explained. This means they will be more likely to work for you.

Serious and life-threatening side effects

Some cancer treatments can cause serious side effects. Sometimes, these may be life-threatening. Your doctor, nurse or pharmacist can explain the risk of these side effects to you.

Your patient alert card

They will also give you a card with information about your treatment. It is important to keep the card with you during treatment and after treatment ends. You should show it to any doctor or healthcare professional caring for you.

Contact the hospital

Your doctor, nurse or pharmacist will give you 24-hour contact numbers for the hospital. If you feel unwell or need advice, you can call at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

Side effects while treatment is being given

Some people may have side effects while they are being given this treatment or shortly after they have it.

Allergic reaction

Some people have an allergic reaction while having this treatment. The first infusion is the most likely to cause a reaction, so it is usually given more slowly than later treatments. Before treatment, you will have medicines to help prevent or reduce any reaction.

Signs of a reaction can include:

  • feeling hot or flushed
  • shivering
  • itching
  • a skin rash
  • feeling dizzy or sick
  • a headache
  • feeling breathless or wheezy
  • swelling of your face or mouth
  • pain in your back, tummy or chest.

Your nurse will check you for signs of a reaction during your infusion. If you feel unwell or have any of these signs, tell them straight away. If you do have a reaction, they can treat it quickly.

Sometimes a reaction happens a few hours after treatment. If you develop any of these signs or feel unwell after you get home, contact the hospital straight away on the 24-hour number.

Redness or swelling at injection site

If you have this treatment as an injection under the skin, the area where you have the injection can become red and swollen (inflamed). This is usually mild and gets better within a few days. Your nurse will put the injection into a different site each time to help with this.

Common side effects

Risk of infection

This treatment can reduce the number of white blood cells in your blood. These cells fight infection. If your white blood cell count is low, you may be more likely to get an infection. A low white blood cell count is called neutropenia.

An infection can be very serious when the number of white blood cells is low. Your doctor may give you antibiotics and other drugs to take during this treatment. These may help reduce your risk of getting an infection. 

But it is still important to get any infection treated as soon as possible. If you have any of the following symptoms, contact the hospital straight away on the 24-hour number:

  • a temperature above 37.5°C 
  • a temperature below 36°C
  • you feel unwell, even with a normal temperature
  • you have symptoms of an infection.

Symptoms of an infection include:

  • feeling shivery and shaking
  • a sore throat
  • a cough 
  • breathlessness
  • diarrhoea
  • needing to pass urine (pee) often, or discomfort when you pass urine.

It is important to follow any specific advice your cancer treatment team gives you.

Your white blood cell count will usually return to normal before your next treatment. You will have a blood test before having more treatment. If your white blood cell count is low, your doctor may delay your treatment for a short time, until your cell count increases.

You may be given a drug called G-CSF. This encourages the body to make more white blood cells. You have it as a small injection under the skin.

Cytomegalovirus (CMV)

CMV is a common virus that many people have been infected with at some point in their lives. Usually CMV infection causes no symptoms, so most people do not know they have had it. Once the virus is in your system, it stays in your body for life. But normally it is inactive (dormant) and does not cause any problems.

If you have this virus, it may become active again while you are having alemtuzumab. Your doctor will give you medicines to help prevent this.

If CMV does become active, it is very important that it is treated. It can often be treated with tablets. Some people may need to have treatment in hospital on a drip (intravenous infusion).

Treatment for CMV can take several weeks. You may need treatment on more than one occasion while you are having alemtuzumab.

Bruising and bleeding

This treatment can reduce the number of platelets in your blood. Platelets are cells that help the blood to clot.

If the number of platelets is low, you may bruise or bleed easily. You may have:

  • nosebleeds
  • bleeding gums
  • heavy periods
  • blood in your urine (pee) or stools (poo)
  • tiny red, brown or purple spots that may look like a rash – these spots can be harder to see if you have black or brown skin. 

If you have any unexplained bruising or bleeding, contact the hospital straight away on the 24-hour number. You may need a drip to give you extra platelets. This is called a platelet transfusion.

Anaemia (low number of red blood cells)

This treatment can reduce the number of red blood cells in your blood. Red blood cells carry oxygen around the body. If the number of red blood cells is low, this is called anaemia. You may feel:

  • very low in energy
  • breathless 
  • dizzy and light-headed. 

If you have these symptoms, contact the hospital straight away on the 24-hour number. You may need treatment for anaemia. If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Skin changes

This treatment can affect your skin. It may cause a rash, which may be itchy. Your doctor or nurse can tell you what to expect. If your skin feels dry, try using soap-free cleansers and unperfumed moisturising cream every day. 

Always tell your doctor or nurse about any skin changes. They can give you advice and may prescribe creams or medicines to help. Changes to your skin usually improve when treatment ends.

Sore mouth and throat

This treatment may cause a sore mouth and throat. You may also get mouth ulcers. This can make you more likely to get a mouth or throat infection. Use a soft toothbrush to clean your teeth or dentures in the morning, at night and after meals.

Contact the hospital straight away on the 24-hour number, if:

  • your mouth or throat is sore, or affecting how much fluid you can drink or food you can eat 
  • your mouth, tongue, throat or lips have any blisters, ulcers or white patches. 

They can give you advice, and mouthwash or medicines to help with the pain or to treat any infection. Follow their advice and make sure you:

  • drink plenty of fluids
  • avoid alcohol and tobacco
  • avoid food or drinks that irritate your mouth and throat.

Diarrhoea

This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is normal for you, or having watery or loose stools. You may also have stomach cramps. If you have a stoma, it may be more active than usual. 

If you are passing loose stools 3 or more times a day and this is not normal for you, contact the hospital as soon as possible on the 24-hour number. Follow the advice they give you about:

  • taking anti-diarrhoea medicines 
  • drinking enough fluids to keep you hydrated and to replace lost salts and minerals
  • any changes to your diet that might help. 

They might also ask you for a specimen of your stool to check for infection.

Tummy pain

You may get pain in your tummy (abdomen), or have indigestion. Your doctor, nurse or pharmacist can give you advice or treatment to help. Contact the hospital straight away on the 24-hour number if your symptoms do not go away, or get worse.

Feeling tired

Feeling tired is a common side effect of this treatment. It is often worse towards the end of treatment and for some weeks after it ends. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can help you feel less tired. 

If you feel sleepy, do not drive or use machinery.

Mood changes

You may have some mood changes during this treatment. You may feel anxious, low or depressed. Tell your doctor or nurse if you notice any changes.

Muscle or joint pain

You may get pain in your muscles or joints for a few days after treatment. If this happens, tell your doctor, nurse or pharmacist. They can give you painkillers and advice. They can also tell you if any of the painkillers you usually take are suitable. 

Tell them if the pain does not get better. Having warm baths and resting regularly may help. 

Effects on the heart

This treatment can affect how the heart works. You may have tests to check how well your heart is working. These may be done before, during and after treatment.

If the treatment is causing heart problems, your doctor may change the type of treatment you are having.

Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

  • breathlessness
  • dizziness
  • changes to your heartbeat
  • swollen feet and ankles.

Other conditions can cause these symptoms, but it is important to get them checked by a doctor. 

Always call 999 if you have:

  • chest pain, pressure, heaviness, tightness or squeezing across the chest
  • difficulty breathing.

Effects on the thyroid

This treatment can sometimes affect the thyroid gland. Your doctor will check how your thyroid is working with regular blood tests. If this happens, it can usually be treated with medication and goes back to normal after the treatment is finished.

Less common side effects

Tumour lysis syndrome (TLS)

Some people are at risk of developing a condition called tumour lysis syndrome (TLS) during this treatment. When treatment makes large numbers of cancer cells die and break down quickly, they release lots of waste products into the blood. This can affect how well the kidneys work. It may also cause problems with the heart rhythm.

TLS can be prevented. You will have regular blood tests to check for TLS. If you are at risk of TLS, you may have:

  • extra fluids through a drip
  • medicines such as rasburicase through a drip, or allopurinol as tablets.

Drinking at least 2 litres (3½ pints) of fluid a day will also help.

Effects on the lungs

This treatment can cause changes to the lungs. Tell your doctor, nurse or pharmacist if you develop: 

  • a cough that does not go away
  • wheezing
  • breathlessness.

You should also tell them if any existing breathing problems get worse. You may have tests to check your lungs.

Effects on the kidneys

This treatment can affect how the kidneys work. This is usually mild and goes back to normal after treatment ends. You will have blood tests to check how well your kidneys are working. Contact the hospital on the 24-hour number if you:

  • have blood in your urine (pee) 
  • are passing less urine or peeing less often than usual.

Drinking fluids helps protect your kidneys. The advice is usually to try to drink at least 2 litres (3½ pints) of fluid each day. But follow any advice from your doctor, nurse or pharmacist about how much is right for you.

Effects on the liver

This treatment can cause liver inflammation and may affect how your liver works. This is called hepatitis. You will have regular blood tests to check this. If the blood tests show liver changes, you may have steroids.

Sometimes liver changes can be serious. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during treatment or after it finishes:

  • yellow skin or eyes
  • feeling very sleepy
  • dark urine (pee)
  • unexplained bleeding or bruising
  • pain in the right side of your tummy (abdomen)
  • loss of appetite.

Eyesight changes

This treatment can affect your eyes and eyesight. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during treatment or after it ends:

  • sore, painful, or swollen eyes
  • eyes that are sensitive to light
  • changes to your eyesight.

You may need steroids or other treatments. A specialist eye doctor (ophthalmologist) may also need to check your eyes.

Effects on the brain

Rarely, this treatment can affect the brain. This can cause symptoms including:

  • drowsiness or confusion
  • memory problems
  • trouble speaking
  • problems with balance, moving or walking
  • changes in eyesight.

Contact the hospital straight away if you have any of these symptoms. If someone with you notices you have any of these symptoms, they should contact the hospital straight away.

It is important not to drive or operate machinery if you have any of these symptoms.

Other information

Blood irradiation

During and after treatment with alemtuzumab, any blood and platelets you are given should first be treated with radiation. This lowers the risk of the donated blood cells reacting against your own. It will not damage the blood or make you radioactive.

Your doctor will record in your medical notes that you should only be given irradiated blood products. They will also give you a card to carry in case you have treatment at another hospital. Always keep this card with you and remind your hospital team that you need irradiated blood or platelets.

Blood clot risk

Cancer and some cancer treatments can increase the risk of a blood clot. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

  • throbbing pain or swelling in a leg or arm
  • reddening of the skin in the area – if you have black or brown skin, this can be harder to notice, but the skin might become darker
  • suddenly feeling breathless or coughing.

Always call 999 if you have:

  • chest pain
  • difficulty breathing.

A blood clot is serious, but it can be treated with drugs called anticoagulants. These thin the blood. Your doctor, nurse or pharmacist can give you more information about preventing and treating blood clots.

Other medicines

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 

Vaccinations

Doctors usually recommend that people with cancer have vaccinations for flu and for coronavirus (covid). These help reduce your risk of serious illness from these infections. Most people can have these vaccines, including people with weak immune systems. 

If your immune system is weak, you should not have live vaccinations. This is because they can make you unwell. Live vaccines, such as the yellow fever vaccine, contain a very weak version of the illness they will protect you against. It is important to ask your doctor, nurse or pharmacist for advice about having vaccinations. They can explain what vaccines are right for you and when it is best to have them.

Contraception

Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment. The drugs may harm a developing baby. It is important to use contraception during your treatment and for 4 months after treatment finishes. Your doctor, nurse or pharmacist can tell you more about this.

Breastfeeding

You are advised not to breastfeed while having this treatment, or for 4 months after treatment finishes. This is because the drugs could be passed to the baby through breast milk.

Your doctor or nurse can give you more information.

Fertility

Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the healthcare professional that you are having cancer treatment. Give them the contact details for your cancer doctor or cancer team so they can ask for advice.

If you have appointments with a dentist, always tell them you are having cancer treatment. Talk to your cancer team before you have any dental treatment.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert health professionals and people living with cancer.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

The language we use

We want everyone affected by cancer to feel our information is written for them.

We want our information to be as clear as possible. To do this, we try to:

  • use plain English
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  • use illustrations to explain text
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We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.

You can read more about how we produce our information here.

Date reviewed

Reviewed: 01 August 2023
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Next review: 01 August 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.