Jakafi (ruxolitinib) can cause side effects that range from mild to serious. More common side effects include dizziness, headache, and anemia. If side effects from Jakafi become difficult to tolerate, talk with your doctor about coping tips or other treatment options.

Jakafi is used to treat:

Jakafi comes as a tablet you take by mouth. It contains the active ingredient ruxolitinib. (An active ingredient is what makes a medication work.) 

Keep reading to learn about the common, mild, and serious side effects that Jakafi can cause. To learn more about Jakafi, including its uses, dosage, and cost, read this Jakafi overview.

More common side effects of Jakafi

The following lists contain some of the more common side effects reported by people who took Jakafi in studies. These side effects can vary depending on the condition being treated.

More common side effects in people taking Jakafi for graft-versus-host disease (GVHD) include:

More common side effects in people taking Jakafi for myelofibrosis and polycythemia vera include:

  • headache
  • dizziness
  • thrombocytopenia
  • anemia
  • diarrhea

For more information about some of these side effects, see the “Side effect specifics” section.

Mild side effects of Jakafi

Mild side effects have been reported with Jakafi. These include:

In most cases, these side effects should be temporary. Some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Jakafi unless your doctor recommends it. 

Jakafi may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

For more information about some of these mild Jakafi side effects, see the “Side effect specifics” section.

Serious side effects of Jakafi

Serious side effects have been reported with Jakafi. These include:

If you develop serious side effects while taking Jakafi, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

For more information about some of these serious Jakafi side effects, see the “Side effect specifics” section.

* Jakafi belongs to a group of drugs called kinase inhibitors. While these side effects weren’t reported in Jakafi studies, they did occur with another kinase inhibitor. Talk with your doctor about your risk of these side effects with Jakafi.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Jakafi, visit MedWatch.

Side effect specifics

Learn more about some of the side effects Jakafi may cause.

Headache

Jakafi may cause headache in some people. This was a common but mild side effect of the drug reported in studies. Headache may have other causes. For example, it may be caused by another side effect of Jakafi, such as anemia (a low level of red blood cells).

What might help

Headache is usually a mild but temporary side effect of Jakafi. But if you have headaches that are bothersome or ongoing, call your doctor. They can determine the cause and discuss ways to manage it. 

Do not take any over-the-counter (OTC) medications without talking with your doctor or pharmacist first. They can tell you what’s safe to take for your headache.

Muscle spasms

Jakafi can cause muscle spasms. This was a mild side effect reported by people taking the drug in studies. In most cases, this should go away as you continue taking Jakafi. Keep in mind, there may be other causes for muscle spasms, such as an injury, or it may be a side effect of other drugs you take.

What might help

If you’re having bothersome muscle spasms during your Jakafi treatment, call your doctor. They can discuss your symptoms with you and suggest ways to manage the spasms. Do not take OTC medication to treat muscle spasms without checking with your doctor or pharmacist first. 

Anemia

In studies of Jakafi, anemia was a common but serious side effect of the drug. With anemia, you have a lower number of red blood cells circulating in your bloodstream. Symptoms of anemia include:

What might help

Before you start taking Jakafi, your doctor will order a complete blood count (CBC). Then they’ll order blood tests every 2 to 4 weeks until your dosage of Jakafi is consistent. They’ll continue to monitor your blood cell counts periodically for as long as you’re taking this medication. 

If you experience symptoms of anemia, call your doctor. They’ll likely order tests to confirm whether your blood cell counts are low. If so, they may lower your dose or temporarily have you stop Jakafi until your blood cell counts recover. For serious anemia, they’ll recommend treatment options such as blood transfusions, if necessary. 

Talk with your doctor if you have questions about this side effect.

Thrombocytopenia

Jakafi can cause low blood cell counts, including thrombocytopenia. This is a serious but common side effect reported in the drug’s studies. With this condition, you have a low level of platelets in your bloodstream. Platelets help with blood clotting to slow or stop bleeding.

Symptoms of thrombocytopenia can include:

What might help

Your doctor will check your blood cell counts before you start and throughout your treatment with Jakafi. If you have symptoms of thrombocytopenia, call your doctor right away. They’ll diagnose your condition and treat your low blood cell counts if needed. In some cases, they may lower your dose of Jakafi or stop it temporarily. This can help improve your blood cell counts.

If you have questions about this side effect of Jakafi, talk with your doctor.

Allergic reaction

For some people, Jakafi can cause an allergic reaction.

But it’s not clear whether this side effect occurred in the drug’s studies.

In general, symptoms of an allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Jakafi. 

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Jakafi, they may have you switch to a different treatment.

Frequently asked questions about Jakafi side effects

Here are answers to some commonly asked questions about Jakafi’s side effects.

Does Jakafi cause long-term side effects?

Yes, in rare cases, Jakafi may cause long-term side effects. Long-term side effects refer to those that happen during treatment and continue, or they may start after you’ve stopped taking the drug. Examples of possible long-term side effects include:

Ask your doctor about your risk for these long-term side effects of Jakafi. They can also tell you how long these side effects may last and ways to lower your risk.

* Jakafi belongs to a group of drugs called kinase inhibitors. While these side effects weren’t reported in Jakafi studies, they did occur with another kinase inhibitor. Talk with your doctor about your risk of these side effects with Jakafi.

Are there any side effects of stopping Jakafi?

It’s possible in certain rare cases. In studies of Jakafi, stopping or lowering the dose of the drug led to worsening of blood cancer symptoms in some people. Symptoms may include:

Your doctor will monitor you carefully for side effects while you’re taking Jakafi. If they need to lower your dose or have you stop the medication, they’ll do it slowly and watch you for serious side effects. 

Do not stop taking Jakafi without talking with your doctor first. They can provide more information about the risks of stopping this medication.

Precautions for Jakafi

Before taking Jakafi, discuss your health history with your doctor. Jakafi may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

Alcohol

Jakafi can increase liver enzyme levels. And drinking too much alcohol could worsen liver-related problems.

If you plan to drink alcohol while taking Jakafi, ask your doctor how much, if any, is safe.

Pregnancy and breastfeeding

It’s not known whether Jakafi is safe to take during pregnancy. If you’re pregnant or planning to become pregnant, ask your doctor if the drug is safe.

It’s not known if Jakafi passes into breast milk. However, there’s a risk of serious blood-related side effects from Jakafi, including thrombocytopenia and anemia. Because of this risk, your doctor will likely suggest not breastfeeding your child during your Jakafi treatment and for 2 weeks after your last dose.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.