Monjuvi (tafasitamab-cxix) is a prescription drug used to treat diffuse large B cell lymphoma. Monjuvi can cause side effects that range from mild to serious. Examples include diarrhea, cough, and fever.

Specifically, Monjuvi is an immunotherapy that helps treat a type of blood cancer called diffuse large B-cell lymphoma (DLBCL).

Monjuvi is prescribed together with another medication called lenalidomide. This drug combination is used in adults with DLBCL that’s returned or hasn’t responded to other treatments and who can’t have a stem cell transplant.

You’ll likely take this combination for up to 12 treatment cycles. Then your doctor will likely have you continue with Monjuvi alone.

The active ingredient in Monjuvi is tafasitamab-cxix*. (An active ingredient is what makes a drug work.) The drug comes as a powder that’s mixed with a liquid to make a solution. A healthcare professional will administer it as an intravenous (IV) infusion (an injection into a vein given over time).

Keep reading to learn about the common, mild, and serious side effects Monjuvi can cause. For a general overview of the drug, including details about its uses, see this article.

* The reason “-cxix” appears at the end of the drug’s name is to show that the drug is distinct from similar medications that may be created in the future.

Some people may experience mild to serious side effects during Monjuvi treatment. But not everyone will have them. A few of the more common side effects reported in Monjuvi studies include:

  • cough
  • fever
  • fatigue (low energy)
  • diarrhea

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

In most cases, these side effects may go away between Monjuvi treatments. And some may be easily managed with a slower infusion or an adjusted dosage. But if you have ongoing or bothersome symptoms, talk with your doctor or pharmacist. And do not stop Monjuvi treatment unless your doctor recommends it.

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

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible with Monjuvi, but this side effect wasn’t reported in studies.

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

A severe allergic reaction* is unlikely but possible with Monjuvi. This side effect wasn’t reported in studies.

If you develop serious side effects from Monjuvi, 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.

* To learn more about this side effect, see the “Side effects explained” section below.

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 Monjuvi, visit MedWatch.

Get answers to some frequently asked questions about Monjuvi’s side effects.

Are side effects of Monjuvi similar to those seen with Mounjaro, Ozempic, or Wegovy?

Monjuvi and Mounjaro have similar-sounding names, but they treat different conditions.

All of these drugs have a few side effects in common, such as diarrhea and decreased appetite. But this is where the similarity ends. Be aware that look-alike and sound-alike drug names can result in treatment errors.

When you’re prescribed a medication, ask for a written or printed note with the drug’s full brand name and generic name, as well as the condition you’re using it to treat. Speak with your pharmacist to ensure your medication matches what your doctor discussed with you.

* The reason “-cxix” appears at the end of the drug’s name is to show that the drug is distinct from similar medications that may be created in the future.
† An active ingredient is what makes a drug work.

Does Monjuvi cause long-term side effects?

It’s not known whether Monjuvi can cause long-term side effects. None were reported in the drug’s studies. If you’re concerned about possible long-term side effects from Monjuvi, talk with your doctor or pharmacist.

Can Monjuvi cause swelling of arms and legs?

Yes. In studies, Monjuvi caused edema (fluid buildup) in the arms, hands, legs, and feet. Effective ways to reduce swelling include:

  • walking
  • stretching the affected areas often
  • propping up your legs or arms while sitting or lying down

Your doctor may also order compression stockings or sleeves for you to help manage swelling.

If you develop tight, weeping, red or discolored areas of swelling, call your doctor right away. These symptoms could indicate a blood clot or infection.

Will weakness and low energy go away after completing Monjuvi treatment?

Yes. Each person will recover from Monjuvi treatments at their own pace. However, low energy can take 90–120 days after completion of treatment to resolve. This is because your bone marrow needs time to replenish your red and white blood cells to usual levels.

Getting enough rest, eating nutritiously, and drinking plenty of fluids will help your body recover from Monjuvi treatment.

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

Life threatening infections

Life threatening infections happened occasionally in studies of Monjuvi. Infection may cause symptoms such as:

Factors that can increase the risk of infection with Monjuvi include:

What might help

If you have symptoms of infection during Monjuvi treatment, talk with your doctor right away. They’ll likely recommend an urgent evaluation to determine whether you need antibiotics or another treatment to boost your white blood cell count.

Infusion reactions

Infusion reactions were an occasional side effect reported in studies of Monjuvi. Infusion reactions may cause symptoms such as:

You may be more likely to have infusion reactions during your first or second infusions of Monjuvi.

What might help

If you have an infusion reaction during Monjuvi treatment, the healthcare professional can stop the infusion and restart it after your symptoms pass. Your doctor may also give you medications before you start a Monjuvi infusion to help prevent a reaction.

Allergic reaction

Like most drugs, Monjuvi can cause an allergic reaction in some people. However, this side effect wasn’t reported in studies. Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, your doctor may suggest a treatment to manage your symptoms. Examples include:

  • an oral antihistamine, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Monjuvi, they’ll decide whether you should continue treatment.

Monjuvi is given at a special infusion clinic or your doctor’s office. So if you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, the healthcare staff will have equipment and medication available to treat you quickly.

If an allergic reaction to Monjuvi develops after you leave the healthcare facility, call your doctor right away. If you experience symptoms that feel like a medical emergency, call 911 or your local emergency number.

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

Keeping track of side effects

During your Monjuvi treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Monjuvi affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before taking Monjuvi.


Monjuvi can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Monjuvi is a good treatment option for you.

Talk with your doctor about your health history before starting Monjuvi. Be sure to tell them if any of the following factors apply to you:

Alcohol and Monjuvi

There are no known interactions between alcohol and Monjuvi. If you drink alcohol and have questions about consuming it during Monjuvi treatment, talk with your doctor or pharmacist.

Pregnancy and breastfeeding with Monjuvi

Before starting Monjuvi treatment, it’s important to talk with your doctor if you’re pregnant, breastfeeding, or planning to be either.


Monjuvi itself is not recommended for use during pregnancy, as it may reduce B cells in a fetus. And you should not use Monjuvi with lenalidomide while pregnant. Lenalidomide may cause problems with fetal development (commonly known as birth defects) or the death of an unborn baby.

If you’re able to become pregnant, your doctor may recommend frequent pregnancy tests and using a reliable form of birth control. They’ll likely recommend that you use birth control for 28 days before starting Monjuvi combined with lenalidomide and throughout your treatment. You may also need to continue taking birth control for at least 3 months after your Monjuvi treatment ends.

If you’re pregnant or planning to become pregnant, talk with your doctor about your treatment options.


Breastfeeding is not safe during and up to 3 months after finishing Monjuvi treatment. If you’re breastfeeding or planning to do so, talk with your doctor about your options.

Like most drugs, Monjuvi can cause side effects that range from mild to serious. However, most are manageable and will go away after you complete Monjuvi treatment. If you have questions about side effects Monjuvi can cause, talk with your doctor.

Examples of questions to help get you started include:

  • What are the most common side effects of Monjuvi?
  • Is my risk of side effects higher when I first begin treatment?
  • What can I do to decrease my risk of side effects?
  • What over-the-counter medications do I need to have on hand to treat Monjuvi side effects?

To learn more about Monjuvi, see these articles:

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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.