7 Kesimpta Side Effects and How to Manage Them

Kesimpta (ofatumumab) is a biologic medication that’s used to treat relapsing forms of multiple sclerosis (MS). MS is a chronic health condition that affects the brain and spinal cord, causing symptoms such as vision changes, weakness, and numbness.

For those who live with MS, medications such as Kesimpta offer a way to manage the condition. But unlike other injectables for MS, which warrant a visit to a medical office or clinic, Kesimpta can be self-administered in the comfort of your own home.

Kesimpta is one of several disease-modifying therapies used to treat MS. It has many potential benefits, but it also has a number of side effects to keep in mind.

Kesimpta side effects at a glance

Kesimpta is a generally well-tolerated medication. But it may take some getting used to. Most Kesimpta side effects get better as you continue taking it and your body adjusts to how it works.

Common Kesimpta side effects include:

• Upper respiratory tract infections

• Headache

• Injection reactions

• Back pain

• Urinary tract infections (UTIs)

While less common, Kesimpta can also raise the risk of serious infections.

Let’s explore seven notable Kesimpta side effects and what you can do to manage them.

1. Respiratory infections

Upper respiratory tract infections — such as the common cold — are the most frequently reported Kesimpta side effects. These respiratory infections may cause symptoms such as a sore throat, runny nose, or headache. They’re typically mild, viral in nature, and should resolve on their own.

If you experience symptoms of a respiratory infection, you may be able to get relief from an over-the-counter (OTC) cold medication. Other remedies and supplements, such as zinc or vitamin C, may also help you kick cold symptoms.

Contact your neurologist if you have cold symptoms that persist or don’t get better. If they think a bacteria is at fault — and not a virus or fungus — they may prescribe you an antibiotic, such as amoxicillin (Amoxil).

2. Injection reactions

Injection reactions are another common side effect of Kesimpta. In clinical studies, both injection site reactions (local) and injection-related reactions (systemic) were reported.

Local reactions

Local injection site reactions are generally more common than systemic ones. Possible signs and symptoms of a local reaction include irritation, pain, and swelling at the site where Kesimpta was injected.

While these reactions usually go away on their own, they can be uncomfortable to experience. But a few simple measures can help relieve symptoms of a reaction:

• Apply a warm compress to soothe irritated areas of skin.

• Wrap an ice pack in a towel and apply it to your injection site to calm symptoms of irritation, warmth and swelling.

• Try an OTC pain reliever, such as Advil (ibuprofen), to help with pain and swelling.

After you inject your first few doses of Kesimpta, you’re less likely to experience these local reactions. Rotating your injection site with each dose can also help prevent more severe reactions.

Systemic reactions

Unlike local reactions, which happen near the injection site, systemic injection reactions can affect other parts of your body. In initial studies, these body-wide reactions were most commonly seen within 24 hours of the first injection. Possible symptoms of a systemic injection reaction include:

• Fever

• Headache

• Muscle pain or weakness

• Chills

• Fatigue

Good to know: The majority of these symptoms tend to be mild to moderate in severity. They also happen less often after the first dose. But reach out to your neurologist without delay if you’re experiencing an injection reaction that’s bothering you or won’t go away.

3. Headache

Headaches are another common side effect of Kesimpta. In initial studies, more than 1 in 10 people treated with Kesimpta were affected by headaches at some point. But headaches can also be related to other triggers, such as dehydration and overexertion, so be sure to stay hydrated and get enough rest.

If you’re looking for a short-term fix for your symptoms, an OTC pain reliever, such as Tylenol (acetaminophen), can help. But managing MS-related pain can be tricky, so contact your neurologist for pain relief recommendations that are best for you.

4. Back pain

Some people experience back pain during treatment with Kesimpta. Experts aren’t sure exactly why this happens. But, if you do develop back pain, there are a few back pain management tips you can try:

• Perform stretches that strengthen your lower back muscles.

• Use heat or ice packs.

• Exercise regularly — and safely.

• Adjust your sleeping position.

• Practice yoga.

• Take an OTC pain reliever, if appropriate.

If you have back pain that becomes problematic, let your neurologist know. There are several ways to treat chronic back pain. But it’s also important to know when to go to the ER for back pain. Seek immediate medical attention if your back pain becomes severe or you notice sudden weakness or numbness in one or both of your legs.

5. Laboratory changes

Kesimpta works by intentionally suppressing parts of your immune system. This helps reduce MS flares. But because your immune system is less active than normal, it's common to see changes in your lab work. Specifically, you may see a change in your immunoglobulin (antibody) levels.

Your neurologist will likely order blood tests to check your immunoglobulin levels before you start Kesimpta and routinely during treatment. If your levels get too low, your healthcare team might consider giving you immunoglobulin infusions for extra support against infection.

6. Urinary tract infections

Kesimpta increases the risk of UTIs. Although UTIs don’t always cause noticeable symptoms, it’s possible to experience:

• Pain or burning while urinating

• Pain in your pelvic area

• Blood in your urine

• Urgent and frequent urination

If you develop symptoms of a UTI, it’s a good idea to seek treatment as soon as possible. If left untreated, the infection could travel up to the bladder or kidneys and cause a more serious problem. Symptoms of an infection in the bladder or kidneys can include nausea or vomiting, back or side pain, and fevers and chills.

If you have any of these symptoms, contact your neurologist as soon as possible. Antibiotics are the only medications that can cure a UTI.

7. Serious infections

Kesimpta lowers your body’s ability to fight infections. In some cases, serious infections, such as pneumonia or progressive multifocal leukoencephalopathy (PML), can develop during treatment with Kesimpta.

PML is a viral brain infection that is serious and potentially life-threatening. Your risk of PML increases when your immune system is less active than normal, which may be due to Kesimpta. 

Contact your neurologist right away if you feel especially under the weather or notice any of the following PML symptoms:

• Weakness that spreads or gets worse over days to weeks

• Vision changes

• Increased clumsiness

• Changes in thinking or memory

• Personality changes

Kesimpta can also reactivate the hepatitis B virus if it’s lingering in your body. Your healthcare team will likely screen you for hepatitis B before you start receiving Kesimpta and on a recurring basis during treatment.

When to contact a healthcare professional about Kesimpta side effects

Most Kesimpta side effects, such as common cold symptoms, headaches, and injection reactions, can be managed at home. But you have any symptoms that are bothersome or concerning, contact your neurologist. Some side effects can get worse if they go untreated, so it’s important to get them addressed, if needed.

Serious Kesimpta side effects, such as serious infections, aren’t common. But they’re still a real and possible risk. Bring up any concerns or noticeable changes to your neurologist right away. They can help figure out the cause of your symptoms and recommend treatment options to get you feeling better.

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Written by:

Taylor K. Clarke, PharmD

Taylor K. Clarke, PharmD, has 8 years of pharmacy experience working in community practice, hospital pharmacy, and ambulatory care pharmacy. Taylor's commitment to patient education motivated her to pursue health communications as a pharmacist.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

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