Key takeaways:
Common Xeljanz (tofacitinib) side effects include upper respiratory tract infections, diarrhea, and headaches. Raised cholesterol is also possible.
Xeljanz raises your risk for serious infections, such as pneumonia. Always tell your prescriber if you’re sick while taking this medication. Depending on your symptoms, they may ask you to temporarily stop taking Xeljanz.
Other rare but serious Xeljanz side effects include heart attack or stroke, blood clots, and a higher risk of cancer. Discuss your risk for these side effects with your prescriber.
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Xeljanz (tofacitinib) is a Janus kinase (JAK) inhibitor that’s prescribed to treat a variety of autoimmune disorders. These disorders include rheumatoid arthritis, ankylosing spondylitis, and ulcerative colitis, among others.
Xeljanz works to treat these conditions by suppressing (weakening) the immune system. But this can also cause side effects.
Xeljanz side effects at a glance
JAK inhibitors, such as Xeljanz, have many possible side effects. Some are mild and can be managed at home. Others are serious and may require medical treatment.
Common Xeljanz side effects include:
Upper respiratory tract infections (URTIs)
Cold-like symptoms, such as a sore throat and runny nose
Diarrhea
Headaches
Raised cholesterol
Raised blood pressure
Nausea
Rare but serious Xeljanz side effects and risks include:
Changes to red and white blood cell counts
Elevated liver enzymes (proteins)
Damage to the stomach or intestine
Severe allergic reactions
This medication also has a few boxed warnings. (A boxed warning is the FDA’s strictest warning for medications.) While rare, the side effects covered by these warnings can be life-threatening.
Xeljanz has boxed warnings because of its potential to increase the risk of:
Serious infections, such as pneumonia
Certain cancers
Death from any cause
Heart attack
Stroke
Blood clots
Below, we’ll discuss what you need to know about nine notable Xeljanz side effects.
1. Upper respiratory tract infections
URTIs, such as sinus infections and the common cold, are a common Xeljanz side effect. Xeljanz’s effects on your immune system make it more likely that you’ll get sick. URTIs may lead to symptoms like a sore throat, a stuffy or runny nose, or sneezing. Other symptoms, like fever and body aches, are also possible.
Many URTIs are caused by viruses, which means they should go away on their own. They don’t usually need to be treated with antibiotics. Though, if you have a URTI that’s caused by bacteria, your healthcare professional may prescribe you an antibiotic.
How to take Xeljanz: Pharmacists review the standard Xeljanz (tofacitinib) dosages for adults and children.
Medications to avoid: Read more about which medications interact with Xeljanz and how to manage these potential interactions.
Comparing options: Xeljanz is one of several Janus kinase (JAK) inhibitors available. Read about how these medications compare, plus ways you can save on them.
You can usually treat the symptoms of a URTI at home with some simple techniques. Staying hydrated and getting enough sleep can both be helpful. You can also take over-the-counter (OTC) cold medication if it’s OK with your prescriber or pharmacist. Reach out to your care team if your symptoms don’t go away after about 1 week or get worse after you’ve tried to treat them at home.
2. Diarrhea
Diarrhea is another common Xeljanz side effect. But keep in mind that diarrhea can have many causes and may be related to the condition you’re treating, such as ulcerative colitis. So it may not be caused by Xeljanz in all cases.
You should be able to manage mild diarrhea at home. But you may need medical attention if you have severe diarrhea.
At-home strategies for managing diarrhea can include:
Avoiding fatty or fried foods
Eating a bland diet for a short period of time
Staying well hydrated
Asking a healthcare professional if you can safely take an OTC antidiarrheal, such as loperamide (Imodium A-D)
If you have diarrhea that seems severe or persistent, tell your prescriber. This isn’t a typical Xeljanz side effect.
3. Headaches
While taking Xeljanz, you could experience headaches. Like other common Xeljanz side effects, mild headaches can be managed at home.
Some strategies to try to relieve or prevent headaches at home include:
Drinking plenty of water
Resting in a dark room
Applying an ice pack to painful areas
Regularly exercising or adding more movement to your routine
Getting enough sleep at night
Limiting caffeine and alcohol
Asking a healthcare professional if you can safely take an OTC pain reliever, such as acetaminophen (Tylenol)
If your headaches are severe or aren’t going away, let your prescriber know. They may suggest adjusting your medication regimen or taking a prescription-only medication to help treat or prevent headaches.
If you have a severe headache along with other symptoms, such as vision changes or weakness on one side of the body, call 911 or go to an ER. These are potential symptoms of a stroke (a rare but serious Xeljanz side effect).
4. Raised cholesterol
Cholesterol is a type of fat that your body needs. But too much cholesterol can increase your risk for blood vessel blockages, which can lead to serious heart-related problems. In clinical studies of Xeljanz, some people taking the medication developed higher cholesterol levels. But researchers aren’t sure if cholesterol changes related to Xeljanz significantly impact the risk of heart-related complications.
Your prescriber will likely check your cholesterol levels from time to time while you’re taking Xeljanz. If your cholesterol becomes too high, they may recommend that you switch to a different treatment or take medication to lower your cholesterol.
5. Serious infections
Xeljanz can raise the risk of serious infections because it lowers your immune response. All JAK inhibitors carry a boxed warning about serious infections. These infections can be caused by bacteria, viruses, or fungi. Infections that have been reported by people taking Xeljanz include pneumonia (a type of lung infection), shingles, and appendicitis.
You shouldn’t take Xeljanz if you have a serious, active infection. You also may need to avoid Xeljanz if you have a history of serious infections or a health condition that raises your risk for infections.
You should watch for symptoms of an infection while you’re taking Xeljanz. This includes fever, chills, and coughing. If you have any of these symptoms, let your prescriber know.
6. Damage to the stomach and intestines
While taking Xeljanz, it’s possible to develop damage or tears in the lining of your stomach or intestines. However, many people who experienced this side effect in clinical studies were also taking nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin), or corticosteroids (“steroids”), such as prednisone. And these medications can also cause damage to the stomach and intestines.
If you have new stomach pain or discomfort while taking Xeljanz, let your prescriber know. They may want to check for possible damage or tears in your stomach or intestines. Depending on your individual risk factors, they may also recommend taking medication to help protect your stomach and intestines.
7. Blood clots
Blood clots are another serious potential Xeljanz side effect. Blood clots in the brain (stroke) or lungs (pulmonary embolism) can be life-threatening. But serious clots can also happen in your legs or arms. Xeljanz has a boxed warning because of the risk of blood clots.
Redness, warmth, or pain in your leg or arm could indicate the presence of a blood clot. If you develop any of these symptoms, contact your prescriber right away.
Trouble breathing, chest pain, or weakness on one side of the body could mean you have a blood clot in the lungs or brain. If you experience any of these symptoms, get help right away by calling 911 or going to the nearest ER.
Let your prescriber know if you have a history of blood clots. They may avoid prescribing you Xeljanz if you have a higher risk of clots.
8. Heart attack or stroke
Very rarely, Xeljanz can cause heart attack and stroke. Because of this, Xeljanz has another boxed warning for these serious cardiovascular complications. In clinical studies, people taking Xeljanz had higher rates of heart attack and stroke compared to those taking biologic medications. However, the risk of these serious side effects is very small.
Your prescriber will carefully consider your risk for heart attacks and stroke before prescribing you Xeljanz.
9. Higher risk of cancer
Xeljanz also carries a boxed warning about the potential for a higher risk of cancer with the medication. In clinical studies, people taking Xeljanz had a higher rate of several types of cancer compared to people taking biologic medications such as Humira (adalimumab). But keep in mind that the risk of developing cancer related to Xeljanz is still very low.
Your prescriber can help you determine your risk for cancer and whether you should avoid taking Xeljanz. If you already have cancer or develop cancer while taking Xeljanz, your prescriber will help you weigh the risks and benefits of either continuing or stopping treatment with the medication.
Frequently asked questions
It’s unlikely that Xeljanz causes weight gain. This side effect wasn’t reported by people taking Xeljanz in clinical trials. But you may be taking other medications with Xeljanz that commonly cause weight gain, such as steroids like prednisone.
If you notice unexpected weight gain while taking Xeljanz, tell your prescriber. They can review your health history and medication list to determine the most likely cause.
It’s recommended to limit or avoid alcohol while taking Xeljanz. While alcohol doesn’t directly interfere with how Xeljanz works, it can worsen certain side effects, such as diarrhea. Drinking can also negatively affect the condition you’re taking Xeljanz to treat. Alcohol, especially regular or heavy use, can contribute to inflammation, potentially worsening your symptoms.
Macrolide antibiotics interact with Xeljanz. Examples of macrolide antibiotics include clarithromycin (Biaxin XL) and erythromycin (Ery-Tab). These medications slow the breakdown of Xeljanz in your body. This can cause Xeljanz to build up, which may lead to more side effects than usual. Your prescriber may temporarily lower your Xeljanz dosage, have you pause treatment, or prescribe a different antibiotic to manage this interaction. But don’t try to change your Xeljanz dosage on your own.
It’s unlikely that Xeljanz causes weight gain. This side effect wasn’t reported by people taking Xeljanz in clinical trials. But you may be taking other medications with Xeljanz that commonly cause weight gain, such as steroids like prednisone.
If you notice unexpected weight gain while taking Xeljanz, tell your prescriber. They can review your health history and medication list to determine the most likely cause.
It’s recommended to limit or avoid alcohol while taking Xeljanz. While alcohol doesn’t directly interfere with how Xeljanz works, it can worsen certain side effects, such as diarrhea. Drinking can also negatively affect the condition you’re taking Xeljanz to treat. Alcohol, especially regular or heavy use, can contribute to inflammation, potentially worsening your symptoms.
Macrolide antibiotics interact with Xeljanz. Examples of macrolide antibiotics include clarithromycin (Biaxin XL) and erythromycin (Ery-Tab). These medications slow the breakdown of Xeljanz in your body. This can cause Xeljanz to build up, which may lead to more side effects than usual. Your prescriber may temporarily lower your Xeljanz dosage, have you pause treatment, or prescribe a different antibiotic to manage this interaction. But don’t try to change your Xeljanz dosage on your own.
The bottom line
Common Xeljanz (tofacitinib) side effects include upper respiratory tract infections, headaches, and diarrhea. Mild side effects can usually be managed at home. But contact your prescriber if you’re having bothersome symptoms that don’t go away.
Rare but serious Xeljanz side effects include blood clots, heart attack, and stroke. Xeljanz may also raise your risk of developing serious infections or certain cancers. Discuss your personal risks for serious side effects with your prescriber before starting treatment with Xeljanz.
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References
Gladman, D. D., et al. (2019). Changes in lipid levels and incidence of cardiovascular events following tofacitinib treatment in patients with psoriatic arthritis: A pooled analysis across phase III and long-term extension studies. Arthritis Care & Research.
Pfizer. (2021). FDA issues update to Xeljanz prescribing information in the United States.
Pfizer Laboratories Div Pfizer. (2025). Xeljanz - tofacitinib tablet, film coated; Xeljanz XR - tofacitinib tablet, film coated, extended release; Xeljanz - tofacitinib solution [package insert].
U.S. Food and Drug Administration. (2022). FDA requires warnings about increased risk of serious heart-related events, cancer, blood clots, and death for JAK inhibitors that treat certain chronic inflammatory conditions.
