Xofluza side effects: what's common, how long they last, when to worry

Xofluza side effects at a glance

Most people who take Xofluza have no side effects. Those who do usually notice mild diarrhea, nausea, or headache. In the prescribing information's adult and adolescent trials, these were reported about as often with placebo (a pill with no medicine in it) as with Xofluza.

The flu itself can cause these symptoms, which may explain the similar rates. In a smaller trial of children 5 to under 12 years old, vomiting (5%) and diarrhea (5%) were the most frequent events. That trial compared Xofluza with oseltamivir and had no placebo group.

Xofluza, known generically as baloxavir marboxil, is taken as a single dose, while other antiviral medications often require multiple doses over several days. It works by inhibiting the cap-dependent endonuclease activity of the viral polymerase, which blocks the influenza virus from replicating in the body. This helps reduce the duration of the flu and minimizes symptom severity, so people can return to their daily activities more swiftly. Learn more about flu symptoms.

Many patients tolerate Xofluza well. Side effects can include nausea, diarrhea, and headache, which are generally mild and transient (short-lived). More serious side effects are rare and may include allergic reactions or severe skin reactions. Watch for unusual changes during treatment and seek timely medical advice if they occur. Always consult a healthcare professional before starting any new medication, especially if you have pre-existing health conditions or take other medications.

CDC does not recommend baloxavir (Xofluza) during pregnancy or breastfeeding, for hospitalized patients, or for people who are severely immunocompromised (have a very weakened immune system). Oseltamivir is the CDC option in those groups. If you are weighing your options, our guide to Xofluza vs Tamiflu explains how these two prescription flu medicines compare on dosing and side effects.

Diarrhea: the most common Xofluza side effect

Diarrhea is a possible side effect of Xofluza. It can cause loose or watery stools, though the flu itself can cause diarrhea too. This usually starts within a day or two of treatment and can last for several days.

Staying hydrated is key when experiencing diarrhea. Drink plenty of water or electrolyte drinks to replace lost fluids. If diarrhea is severe, causes dehydration, or lasts more than a few days, contact your doctor for advice.

Nausea and vomiting

Nausea is a possible side effect for people taking Xofluza. You might feel queasy or even vomit shortly after taking the pill. This side effect usually appears soon after the first dose and can last a few hours to a couple of days.

To reduce nausea, try taking Xofluza with a light snack or a full glass of water. Avoid greasy or heavy meals while your stomach feels sensitive. If nausea becomes severe or lasts longer than a few days, it’s a good idea to check in with a healthcare provider.

In addition to nausea, some individuals may also experience a general feeling of discomfort in their stomach, which can be accompanied by bloating or gas. This discomfort can be particularly distressing, especially if you are already feeling unwell due to the flu. Staying hydrated is crucial; sipping on clear fluids like ginger ale or herbal teas can help soothe your stomach. Ginger, in particular, is known for its anti-nausea properties and can be a gentle remedy to alleviate symptoms.

Another helpful tip is to engage in light, calming activities that can distract you from the discomfort. Gentle walks or practicing deep breathing exercises can help ease the queasiness. However, if you find that your symptoms are persistent or worsening, it’s essential to consult with a healthcare professional who can provide guidance tailored to your specific situation. They may recommend alternative treatments or medications that can help manage these side effects more effectively. Many people searching for Xofluza and nausea want to know whether the medicine or the flu is behind it, and the placebo comparison above suggests the flu itself may explain much of the queasiness.

Headache

Some people report headaches after taking Xofluza. This side effect can range from mild to moderate and may feel like a tension headache or pressure around the head. Headaches often start within the first day of treatment and usually go away on their own.

Over-the-counter pain relievers like acetaminophen or ibuprofen can help ease headaches. Make sure to follow the dosing instructions. If headaches are very painful, persistent, or accompanied by other symptoms such as vision changes, seek medical help promptly.

How long do Xofluza side effects last?

Most Xofluza side effects are mild and fade within a few days of your single dose. If you get diarrhea, nausea, or a headache, it usually shows up early and settles on its own as your flu improves. Symptoms that last longer than a few days, or get worse, are worth a call to your doctor.

Xofluza stays in your body longer than many flu antivirals, which is why one dose covers the whole treatment. That does not mean side effects last that long. Stomach upset typically eases within days. The flu itself can cause nausea, diarrhea, and headache, so it can be hard to tell which one is behind your symptoms.

What to expect:

• Nausea, vomiting, or diarrhea: These tend to start soon after the dose and ease within a few days. Keep sipping fluids while they last.
• Headache: This is usually mild and goes away without treatment.
• Allergic or skin reactions: Rash, swelling of the face or throat, or trouble breathing can happen at any point after the dose. Do not wait these out. Get emergency care right away.

If you are unsure whether what you feel is the flu or the medicine, note when your symptoms began and how they change each day. That timeline helps your doctor decide whether anything needs to change. Knowing how long Xofluza stays in your system explains why one dose covers the whole treatment, but side effects usually fade within a few days either way.

Does Xofluza make you tired or drowsy?

No, Xofluza is not known to cause drowsiness as a common side effect, so tiredness while you take it is most likely the flu itself. Fatigue (deep, whole-body exhaustion) is a hallmark flu symptom and can linger for days after the fever breaks. Your body is working hard to fight the virus, and that may leave you wiped out whether or not you take the pill.

The prescribing information lists the side effects reported in at least 1% of adults and adolescents: diarrhea (3%), bronchitis (3%), nausea (2%), sinusitis (2%), and headache (1%). Sleepiness is not on that list. Each of those events showed up at similar or lower rates than with placebo (a pill with no medicine in it).

Tiredness can still have other causes while you recover:

• Dehydration: Vomiting or diarrhea can drain your energy. Keep sipping fluids.
• Poor sleep: Fever, coughing, and aches can disrupt rest.
• Not eating much: A small snack may help you feel steadier.

Call your doctor if the tiredness gets worse after the first few days instead of better, or if you develop shortness of breath, chest pain, or confusion. These may signal a flu complication. Tiredness together with rash, swelling of the face or throat, or trouble breathing could be an allergic reaction. Get emergency care right away.

Xofluza side effects in kids

Xofluza is approved for children 5 and older, and vomiting and diarrhea are the side effects parents see most. Most kids handle the single dose well, and stomach symptoms usually pass within a few days. Rare allergic reactions need emergency care, so know the warning signs.

In the prescribing information's trial of 79 children ages 5 to under 12, vomiting (5%) and diarrhea (5%) were the most frequent side effects. That trial compared Xofluza with oseltamivir, not placebo (a pill with no medicine in it). The flu itself can cause the same symptoms, so the numbers do not show how much of it the medicine caused. Before giving your child a dose, review Xofluza interactions with dairy products, calcium-fortified drinks, antacids, and mineral supplements.

Xofluza is approved for people 5 and older for uncomplicated flu treatment (started within 48 hours of the first symptoms) and for post-exposure prophylaxis (preventing flu after contact with someone who has it). Watch for:

• Dehydration: Little urine, a dry mouth, no tears, or unusual sleepiness after repeated vomiting or diarrhea. Offer small, frequent sips of fluid.
• Allergic reaction: Rash, itching, swelling of the face or throat, or trouble breathing. Get emergency care right away.
• Symptoms that last or worsen: Call your child's doctor if stomach upset continues beyond a few days.
• Dairy and supplements: The label says to avoid taking Xofluza with dairy products, calcium-fortified drinks, antacids, or calcium, iron, magnesium, selenium, or zinc supplements.

Serious side effects: allergic and skin reactions

Though uncommon, Xofluza may cause serious allergic (hypersensitivity) reactions, including anaphylaxis (a severe, whole-body allergic reaction) and serious skin reactions. Symptoms to watch for include rash, itching, swelling of the face or throat, or trouble breathing.

If you experience any of these symptoms, get emergency care right away. Early detection and treatment can prevent more serious complications.

How to ease Xofluza side effects

• Take medicine with food: Taking Xofluza with a small meal or snack can help reduce nausea and stomach upset. The label says the dose may be taken with or without food, so a snack is optional.
• Stay hydrated: Drinking plenty of fluids helps manage diarrhea and prevent dehydration (when your body loses too much water). Water, herbal teas, and electrolyte drinks are good choices. Keep sipping throughout the day while symptoms last.
• Rest and monitor symptoms: Resting while your body fights the flu and the medication works is important. Keep track of any side effects and how long they last. If symptoms worsen or new ones appear, seek medical advice.

Can you take Xofluza on an empty stomach?

Yes, you can take Xofluza on an empty stomach. The label says the single dose may be taken with or without food, so a snack is optional. What matters more is what you take it with, because some foods and products can keep the medicine from working as well.

Avoid these at the time of your dose:

• Dairy products: Milk, yogurt, and cheese.
• Calcium-fortified drinks: Some juices and plant milks.
• Laxatives and antacids: Products that contain calcium, aluminum, or magnesium.
• Mineral supplements: Calcium, iron, magnesium, selenium, or zinc.

These products contain minerals that may bind to baloxavir (the active drug in Xofluza) in your gut, which may lower how much your body absorbs. Water is a safe choice for swallowing the tablet. If you feel queasy, a light snack without dairy may help settle your stomach.

Xofluza is approved for people 5 and older for uncomplicated flu and for post-exposure prophylaxis (preventing flu after contact with someone who has it). Take it as soon as possible and within 48 hours of your first flu symptoms. If you are unsure whether your usual supplements or antacids are a problem, ask your pharmacist or doctor before you take the dose.

Who should not take Xofluza

Xofluza (baloxavir) is not recommended if you are pregnant or breastfeeding, hospitalized with flu, or severely immunocompromised (have a very weakened immune system). The CDC cites limited information on how the drug works in these groups. Oseltamivir is the CDC option for them, so ask your doctor about it instead.

Other people who should not take it:

• Anyone allergic to Xofluza: The label lists a known allergy as a contraindication (a reason not to use it). Anaphylaxis (a severe, whole-body allergic reaction), hives, swelling, and a serious skin rash have been reported.
• Children under 5: The label says Xofluza is not indicated at this age because the flu virus became resistant to it more often (it stopped responding to the drug).
• Outpatients with complicated or worsening flu: The CDC does not recommend it for this group either.

Xofluza is approved for people 5 and older for uncomplicated flu and for post-exposure prophylaxis (preventing flu after contact with someone who has it). If you fall into one of the groups above and have flu symptoms, call your doctor promptly. Antivirals work best when started early, and the label sets a window of within 48 hours of your first symptoms.

When to contact your doctor about Xofluza side effects

Most side effects of Xofluza are mild and go away on their own. Contact your doctor if you experience:

• Severe or persistent nausea, vomiting, or diarrhea
• Signs of an allergic reaction, such as rash, swelling, or difficulty breathing (get emergency care right away)
• Severe headaches or dizziness

For quick answers about side effects, Doctronic's AI doctor can help you decide whether you need a visit with a licensed clinician. If you have not started treatment yet and need a prescription, you can get Xofluza prescribed online without waiting for an in-person appointment.

Frequently Asked Questions

Can I take Xofluza if I have a history of allergies?

Tell your doctor about any allergies before starting Xofluza. If you have had allergic reactions to similar antiviral drugs, your doctor may recommend a different treatment.

How long do Xofluza side effects usually last?

Most side effects, such as nausea, headache, and diarrhea, last a few days after starting treatment. If they persist longer, contact your healthcare provider.

Is it safe to take other medications with Xofluza?

Always check with your doctor or pharmacist before combining medications. Xofluza may interact with certain drugs, so professional advice is important.

What should I do if I miss a dose of Xofluza?

Xofluza is taken as a single dose, so there is no next dose to schedule. If you have not taken it yet, it works best when taken as soon as possible and within 48 hours of when flu symptoms began. If you are unsure whether you took it, or more than 48 hours have passed, ask your doctor or pharmacist what to do.

Can children take Xofluza?

Xofluza is approved for people 5 and older for uncomplicated flu and for post-exposure prophylaxis (preventing flu after contact with someone who has it). For younger children, other flu treatments may be recommended.

The Bottom Line

Most people tolerate this single-dose flu treatment well, with manageable digestive side effects that resolve quickly, but serious allergic or skin reactions demand immediate medical attention. Xofluza may be taken with or without food, and avoiding dairy, calcium, and mineral supplements at dose time helps the medicine work as intended.