If you have moderate to severe plaque psoriasis or psoriatic arthritis, your doctor may recommend treatment with Tremfya (guselkumab). Knowing more about the possible side effects of Tremfya can help you decide if this drug may be right for you.

Tremfya is given as an injection under your skin. If it works for you without causing troublesome side effects, you’ll likely take it long term. Tremfya is a biologic medication, meaning it’s made from parts of living cells.

For more information about Tremfya, including details about its uses, see this in-depth article.

Like other drugs, Tremfya injections can cause mild or serious side effects. Your doctor will only recommend Tremfya for you if they feel its benefits are likely to outweigh its risks.

Keep reading to learn more about the drug’s possible side effects.

Some people may experience mild or serious side effects while using Tremfya. Examples of Tremfya’s most commonly reported side effects include:

Other side effects are also possible with Tremfya. Read on to learn more.

* For more information on this side effect, see the “Side effects explained” section below.

Most of the side effects reported with Tremfya are mild. Examples of these mild side effects include:

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

In most cases, these side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And don’t stop using Tremfya unless your doctor tells you to.

Tremfya may cause mild side effects other than the ones listed above. For more information, see the Tremfya medication guide.

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 Tremfya, visit MedWatch.

Serious side effects that have been reported with Tremfya include:

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

* An allergic reaction is possible after using Tremfya. However, it’s not clear whether this side effect occurred in studies

Here are the answers to some frequently asked questions about Tremfya’s side effects.

Does Tremfya cause depression?

No, it’s not known to. Some other psoriasis treatments have been associated with depression, but depression wasn’t reported in studies of Tremfya.

If you have a long-term condition such as plaque psoriasis, it’s common to have episodes of low mood or to experience depression. Your mood and outlook may get better if you use a treatment that improves the symptoms of your condition. However, it’s important to talk with your doctor if you’re feeling low, sad, or discouraged. There are many treatments available for depression.

Will I gain weight during my Tremfya treatment?

No, Tremfya doesn’t cause weight gain. This side effect wasn’t reported in studies of Tremfya.

If you experience unexplained weight gain, talk with your doctor. They can try to determine the reason you may be gaining weight.

Could I experience hair loss while using Tremfya?

No, it’s not likely. Hair loss wasn’t reported in studies of Tremfya.

If you have scalp psoriasis, this can sometimes lead to patchy hair loss, especially if your scalp gets irritated from scratching.

If you experience hair loss that bothers you, talk with your doctor to learn about possible causes and treatments.

Here’s some more detail about some of the side effects Tremfya may cause.

Injection site reactions

Some people may have an injection site reaction after their Tremfya treatment. This is usually a mild side effect. Injection site reactions were commonly reported in studies of Tremfya.

With an injection site reaction, you may have one or more of the following symptoms at the place where you had your injection:

  • redness or discoloration
  • swelling
  • bruising
  • pain
  • itching
  • hard lump under the skin

What might help

To help prevent injection site reactions:

  • Each time you give yourself an injection, change the injection site.
  • Avoid injecting the drug into spots that are red or discolored, tender, bruised, hard, or affected by psoriasis.

If you have an injection site reaction, avoid rubbing the area or applying creams or lotions. If needed, you can help ease discomfort by:

  • applying a cold pack to reduce swelling, itching, or pain
  • taking an over-the-counter pain reliever, such as Tylenol (acetaminophen) if needed

Injection site reactions usually get better on their own in a few days. But talk with your doctor if you have a reaction that doesn’t get better or that seems severe.

Upper respiratory infection

Tremfya may cause an upper respiratory infection such as the common cold. This is because Tremfya can weaken your immune system and make it less able to fight off germs that cause infection. Upper respiratory infections were the most commonly reported side effect in studies of Tremfya.

Upper respiratory infections affect the linings of your nose and throat. They’re usually mild and may cause symptoms such as:

  • runny nose
  • stuffy or blocked nose
  • sneezing
  • sinus pain
  • sore throat
  • tickly cough

What might help

You can help prevent upper respiratory infections by:

  • washing your hands or using hand sanitizer frequently, especially if you’ve been in a public place
  • avoiding crowds when possible
  • staying away from people who are sick
  • eating a balanced diet containing plenty of fruit and vegetables

If you do get a cold, be sure to drink plenty of fluids and get lots of rest. There are also many home remedies and over-the-counter medications you can use to ease your symptoms. For example:

  • for a stuffy nose:
    • lemon or ginger tea
    • decongestant tablets or nasal (nose) sprays, such as pseudoephedrine (Sudafed) or oxymetazoline (Afrin)
    • saline nasal sprays or drops
  • for a sore throat or tickly cough:
    • honey and lemon tea
    • sore throat lozenges
    • cough syrup
    • cough suppressants, such as dextromethorphan (Delsym, Robitussin)
  • for a runny nose or sneezing:

You could also try home remedies that may help stimulate your immune system, such as echinacea, vitamin C, zinc, and garlic.

Always talk with your doctor or pharmacist before using any new medications. They can help you find the right treatment, taking into account any other medications you take and other conditions you may have. Your pharmacist can also give you advice about home remedies.

Talk with your doctor if you have a respiratory infection that starts to get worse or that doesn’t get better after about a week. Also tell your doctor if you have a fever, sweats, chills, shortness of breath, or if you cough up blood. These could be signs of a more serious respiratory infection, which your doctor may need to prescribe medication to treat.

Stomach flu

Some people may get stomach flu while taking Tremfya. This is because the drug can weaken your immune system and make it less able to fight off germs that cause infection.

Stomach flu is an infection that you’re more likely to get if your immune system is weaker than usual. But in studies of Tremfya, this side effect was reported less often than respiratory infections (see “Upper respiratory infection” section above).

Symptoms of stomach flu can include:

  • diarrhea
  • nausea and vomiting
  • abdominal (belly) pain
  • gas
  • loss of appetite
  • fever or chills
  • sweating
  • achiness

What might help

You can help prevent stomach flu by:

  • washing your hands frequently, especially after using the bathroom and before preparing or eating food
  • avoiding sharing cutlery, plates, or towels with anyone who has symptoms of stomach flu
  • washing fruits and vegetables thoroughly before eating
  • avoiding eating raw or undercooked foods

If you have symptoms of stomach flu, it’s important to get lots of rest and drink plenty of fluids to avoid dehydration. You can also try:

  • drinking sports drinks or rehydration solutions, such as Pedialyte, to replace lost fluids and electrolytes
  • eating bland foods such as rice, potatoes, toast, or bananas until you feel better
  • avoiding fruit juices, sugary or fatty foods, and dairy products until you feel better
  • taking over-the-counter medication for diarrhea, such as Imodium (loperamide), if recommended by your doctor

Stomach flu usually clears up on its own within 2 to 3 days. But talk with your doctor if you have symptoms that last longer than this or get worse.

Also tell your doctor if you have blood in your stool, can’t keep fluids down, or have symptoms of dehydration (water loss in the body). Dehydration symptoms may include excessive thirst, dry mouth or skin, headache, and urinating less than usual.

Herpes

Herpes, such as cold sores or genital herpes, has occurred in some people using Tremfya.

Herpes is caused by a virus. Symptoms can include:

  • flu-like symptoms, such as fever or sore throat
  • tingling, itching, or burning sensation around your mouth
  • small, painful, fluid-filled sores on your lips, cheeks, chin, or inside your nostrils
  • small, painful, fluid-filled sores on or around your genitals

Tell your doctor if you’ve had herpes in the past, because taking Tremfya could make it flare up again.

What might help

To help prevent herpes, you should:

  • avoid sharing facecloths, towels, lip balms, or lipsticks with others
  • avoid close contact, such as kissing or sexual contact, with someone who has an active herpes infection

If you develop herpes, it can be easily treated with antiviral drugs. For example, cold sores can be treated with over-the-counter (OTC) creams such as Abreva (docosanol). For genital herpes, you’ll need antiviral medication prescribed by a doctor, such as:

  • Zovirax (acyclovir)
  • Valtrex (valacyclovir)

Talk with your doctor or pharmacist if you think you have herpes while using Tremfya. They can recommend a suitable antiviral. They can also suggest other medications to help ease your pain or discomfort. Examples of these medications include local anesthetic gels such as Blistex and OTC pain relievers, such as Tylenol (acetaminophen).

Tell your doctor if your infection doesn’t clear up, gets worse, or spreads.

If you’ve had herpes in the past, talk with your doctor before using Tremfya. They may recommend taking an antiviral on a regular basis to help prevent flare-ups of the herpes infection during your Tremfya treatment.

Allergic reaction

Like most drugs, Tremfya can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in studies.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically 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, call your doctor right away. They may suggest an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, like hydrocortisone cream, to manage your symptoms.

If your doctor confirms you had a mild allergic reaction to Tremfya, they’ll decide if you should continue using it.

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 had a serious allergic reaction to Tremfya, they may have you switch to a different treatment.

Keeping track of side effects

During your Tremfya treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things like:

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

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

Tremfya may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Tremfya. Factors to consider include those in the list below.

Infections. Taking Tremfya can raise your risk for infection. If you currently have an infection, it will likely need to be treated before you can start Tremfya. Tell your doctor if you have an ongoing infection or a history of infections that keep coming back. Your doctor will determine if Tremfya is right for you.

Tuberculosis (TB). Your doctor will likely test you for TB before you start Tremfya. If you have an active TB infection, it will need to be treated before you start using Tremfya. If you’ve had TB in the past, taking Tremfya could make TB flare up in your body again. Your doctor will likely prescribe medication to help prevent this.

Allergic reaction. If you’ve had an allergic reaction to Tremfya or any of its ingredients, you shouldn’t take Tremfya. Ask your doctor what other medications are better options for you.

Alcohol use and Tremfya

Alcohol doesn’t interact with Tremfya specifically. But alcohol use may affect your plaque psoriasis or psoriatic arthritis. And like Tremfya, it might make it harder for your immune system to fight germs that can cause infections.

If you drink alcohol, talk with your doctor about how much is safe for you to drink with your condition.

Pregnancy and breastfeeding while taking Tremfya

It’s not known if Tremfya is safe to use while pregnant or breastfeeding. If you’re pregnant or breastfeeding, or planning to become pregnant or to breastfeed, talk with your doctor before using Tremfya.

Tremfya may be effective in treating your plaque psoriasis or psoriatic arthritis. But the drug may also cause side effects in some people. In most cases, side effects from Tremfya are mild.

If you have questions about Tremfya’s side effects, talk with your doctor or pharmacist. Examples of questions you might want to ask include:

  • Do I have a higher risk for infection with Tremfya than other people?
  • Are there any vaccinations I should receive before starting treatment? Are there vaccines I can’t get while using Tremfya?
  • Does using Tremfya raise my risk for getting COVID-19? Can I receive the COVID-19 vaccine during my treatment?

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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 other 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.