Ruxolitinib (Jakavi)

Ruxolitinib is a type of targeted cancer drug. It is also known as Jakavi.

You have it as a treatment for some myeloproliferative neoplasms such as:

  • myelofibrosis
  • polycythaemia vera

You might also have ruxolitinib as part of a clinical trial Open a glossary item for another type of myeloproliferative neoplasm.

How does ruxolitinib work?

Ruxolitinib is a type of targeted cancer drug called a cancer growth blocker.  A cancer growth blocker blocks the growth factors Open a glossary item that trigger the cancer cells to divide and grow. Ruxolitinib works by blocking a gene Open a glossary item that is important in the making of blood cells Open a glossary item. This gene is called Janus Associated Kinases 1 or 2 (JAK 1 or JAK2).

You have a blood test to check for the JAK gene change before you start treatment.

How do you take ruxolitinib?

You take ruxolitinib as tablets, usually twice a day. The amount (dose) might change depending on the results of your blood tests. Your doctor will tell you if you need to change the dose.

You can take them with or without food, at the same time each day.

You must take tablets according to the instructions your doctor or pharmacist gives you.

You should take the right dose, not more or less.

Talk to your healthcare team if you miss a dose or you want to stop taking a cancer drug. You may feel unwell if you stop taking ruxolitinib suddenly.

How often do you take ruxolitinib?

You continue taking ruxolitinib for as long as the treatment is working, and you are not experiencing too many side effects.


You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

What are the side effects of ruxolitinib?

Side effects can vary from person to person. They also depend on what other treatments you're having. 

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better. 

Contact your advice line immediately if you have signs of infection, including a temperature above 37.5C or below 36C.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects. But you might have some of them at the same time.

The side effects are different for people having ruxolitinib for myelofibrosis and people having ruxolitinib for polycythaemia vera.

Common side effects

These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:

Urinary tract infections (UTIs)

Symptoms of a UTI might include difficulty to passing urine, wanting to go with some urgency or are going more often. There may be pain or burning when you go. You may see blood in your urine, or your urine might smell bad or look cloudy. Tell your doctor or nurse if you think you might have a urinary tract infection.

Low levels of red blood cells (anaemia)

You might be breathless and look pale due to a drop in red blood cells. This is called anaemia.

Bruising, bleeding gums or nose bleeds

This is due to a drop in the number of platelets in your blood. These blood cells help the blood to clot when we cut ourselves. You may have nosebleeds or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechiae).

Ruxolitinib can also cause bleeding from anywhere in your body. Signs of bleeding from other parts of the body include blood in your urine or poo (stool), black stool, vomiting or coughing up blood, headaches, dizziness or feeling weak.

Contact your doctor or nurse straight away if you have any signs of bleeding.

Weight gain

You may gain weight while having this treatment. You may be able to control it with diet and exercise. Tell your healthcare team if you are finding it difficult to control your weight. 

High cholesterol and other fats in your blood

Cholesterol is a fatty substance which helps cells in the body to work normally. When the cholesterol level is too high it could have an effect on your heart. You usually have blood tests to check your cholesterol levels and other fats in your blood. You may also start medicine to manage this.


Let your doctor or nurse know if you have headaches. They can give you painkillers such as paracetamol to help.


This drug might make you feel dizzy. Don’t drive or operate machinery if you have this.

Liver changes

You might have liver changes while taking this drug. You have regular blood tests to check for any changes in the way your liver is working.

High levels of pancreatic enzymes in your blood

You might have high levels of substances (enzymes) called lipase in your blood. This doesn't usually cause symptoms. Changes in the enzyme levels usually return to normal when you stop the drug.


Constipation Open a glossary item is easier to sort out if you treat it early. Drink plenty of fluids and eat as much fresh fruit and vegetables as you can. Try to take gentle exercise, such as walking. Tell your healthcare team if you think you are constipated. They can prescribe a laxative.

High blood pressure

Tell your doctor or nurse if you have headaches, nosebleeds, blurred or double vision or shortness of breath. Your nurse checks your blood pressure regularly. 

It’s common for people taking ruxolitinib for myelofibrosis to be at an increased risk of getting an infection. This is less common if you take ruxolitinib for polycythaemia vera.

Increased risk of getting an infection is due to a drop in white blood cells. Symptoms include a change in temperature, aching muscles, headaches, feeling cold and shivery and generally unwell.

You might have other symptoms depending on where the infection is, such as inflammation of the lungs (pneumonia). Symptoms might also include a cough, shortness of breath, you may wheeze when you breathe, chest pain and feeling very tired. 

Infections can sometimes be life threatening. You should contact your advice line urgently if you think you have an infection.

Occasional side effects

You might get wind (flatulence). This happens in between 1 and 10 out of every 100 people (between 1 and 10%).

For people taking ruxolitinib for myelofibrosis occasionally it can cause a serious reaction to an infection also known as sepsis. This is rare if you take ruxolitinib for polycythaemia vera.

Signs can include feeling very unwell, not passing urine, being sick, a very high or very low temperature or shivering - contact your advice line straight away if you have any of these symptoms.

Other side effects

There is a risk with ruxolitinib that you might develop a non melanoma skin cancer particularly if you have had previous treatment with hydroxycarbamide.

It isn’t known if ruxolitinib is the cause so your healthcare team will advise you to protect your skin in the sunlight and regularly check for any skin changes.

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do you need to know?

Other medicines, food and drink

Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.

Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.

Loss of fertility

It is not known whether this treatment affects fertility. Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Pregnancy and contraception

It is unknown whether treatment may or may not harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment.

Talk to your doctor or nurse about effective contraception you can use during treatment. Ask how long you should use it before starting treatment and after treatment has finished.


It is not known whether this drug comes through into the breast milk. Doctors usually advise that you don’t breastfeed during this treatment.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment if you need treatment for anything else, including teeth problems.


Don’t have immunisations with live vaccines while you’re having treatment and for up to 12 months afterwards. The length of time depends on the treatment you are having. Ask your doctor or pharmacist how long you should avoid live vaccinations.

In the UK, live vaccines include rubella, mumps, measles, BCG, yellow fever and one of the shingles vaccines called Zostavax.

You can have:

  • other vaccines, but they might not give you as much protection as usual
  • the flu vaccine (as an injection)
  • the coronavirus (COVID-19) vaccine - talk to your doctor or pharmacist about the best time to have it in relation to your cancer treatment

Members of your household who are aged 5 years or over are also able to have the COVID-19 vaccine. This is to help lower your risk of getting COVID-19 while having cancer treatment and until your immune system Open a glossary item recovers from treatment.

Contact with others who have had immunisations - You can be in contact with other people who have had live vaccines as injections. Avoid close contact with people who have recently had live vaccines taken by mouth (oral vaccines) such as the oral typhoid vaccine. Sometimes people who have had the live shingles vaccine can get a shingles type rash. If this happens they should keep the area covered.

If your immune system is severely weakened, you should avoid contact with children who have had the flu vaccine as a nasal spray as this is a live vaccine. This is for 2 weeks following their vaccination.

Babies have the live rotavirus vaccine. The virus is in the baby’s poo for about 2 weeks and could make you ill if your immunity is low. Get someone else to change their nappies during this time if you can. If this isn't possible, wash your hands well after changing their nappy.

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

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