Key takeaways:
Xofluza (baloxavir marboxil) works by stopping the flu virus from replicating in the body. You only need one dose of Xofluza, but you need to take it within 48 hours (2 days) of feeling flu symptoms.
Xofluza starts working in about 4 hours, but it may take up to 2 days before your flu symptoms go away. In the meantime, it’s fine to take most over-the-counter flu medications with Xofluza if you need them.
There are ways to save on Xofluza. If you’re eligible, a manufacturer savings card can help you get Xofluza for as little as $30 per dose.
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Xofluza (baloxavir marboxil) is a one-dose prescription medication that can help you feel better faster when you have the flu (influenza virus). It can also help you avoid getting the flu if you’ve recently been exposed to it.
Xofluza is safe for adults and children ages 5 and older. But how does Xofluza work? And how long does it take before you’ll start feeling better? Let’s review these and more commonly asked questions about Xofluza.
1. How does Xofluza work?
Xofluza is an endonuclease inhibitor. Endonuclease is an enzyme (protein) that helps the flu virus make copies of itself. These copies spread the flu infection in your body. Xofluza blocks this enzyme, preventing the flu virus from replicating and stopping the infection process.
Xofluza is most effective if you take it within 48 hours (2 days) of the start of your flu symptoms, before the virus is widespread in your body. So it’s best to contact a healthcare professional for a prescription and take your dose as soon as possible after flu symptoms appear.
2. How long does it take Xofluza to work?
Xofluza can start taking action against the flu virus within 4 hours of your dose. But it will likely take longer than that for you to start feeling better.
In most cases, your symptoms will gradually improve after you take Xofluza. In clinical studies, people reported mild or no flu symptoms about 2 days after their dose.
If it’s been 2 days or more and your symptoms aren’t improving or are getting worse, contact your healthcare team. Sometimes, the flu can lead to the development of other issues, including bacterial infections, that may need additional treatment with other medications.
3. How long does Xofluza stay in your system?
It takes a little over 2 weeks for your body to process and clear Xofluza. During this time, the medication will continue fighting your flu infection.
Xofluza’s long-lasting activity is the main reason you only need to take one dose of the medication. This makes it a more convenient option than other flu treatment options for a lot of people.
4. How often can you take Xofluza?
You should only take Xofluza once for each case of the flu you have or are exposed to.
For instance, if you take Xofluza the day your flu symptoms start but you still don’t feel well a week later, you shouldn’t take another dose. But if you had the flu and used Xofluza to clear it up, and you get the flu again weeks or months later, you may be able to take another dose of Xofluza.
Your prescriber can help decide if and when Xofluza is right for you.
Xofluza side effects: Learn what side effects are possible while taking Xofluza (baloxavir marboxil) and how to manage them if they occur.
Medication alternatives: Discover simple home remedies that can help ease your flu symptoms naturally.
Tips for taking Xofluza: Read these pharmacist-backed tips for taking Xofluza to help you get the most from your medication.
5. Can you take Xofluza with OTC flu medications?
Yes, it’s fine to take Xofluza with over-the-counter (OTC) medications for your flu symptoms. This includes pain and fever relievers, such as Tylenol (acetaminophen) or Advil (ibuprofen). Medications for a stuffy nose or cough, such as Sudafed (pseudoephedrine) or Delsym (dextromethorphan), are also fine to take with Xofluza.
But you should avoid antacids, laxatives, or supplements that contain any of the following ingredients:
These ingredients can bind to Xofluza and make it less effective. So you should avoid them the day you take Xofluza. If you’ve already consumed one of these ingredients, or any foods that are high in calcium, wait 4 to 5 hours before taking your Xofluza dose.
Good to know: Zinc is a common ingredient in OTC products marketed to help prevent and relieve cold and flu symptoms. So be sure to check the label of any OTC products you’re taking and avoid them within 4 to 5 hours of your Xofluza dose if they contain zinc.
6. Is Xofluza safe to take if you’re pregnant?
Xofluza is not recommended if you’re pregnant or breastfeeding. There isn’t enough data to know if it’s safe. But that doesn’t mean you can’t get treatment.
Tamiflu (oseltamivir) is the first-choice medication to treat the flu if you’re pregnant. It’s also considered safe to prevent the flu if you’re exposed to it while pregnant.
How to save on Xofluza
Xofluza is only available as a brand-name medication. GoodRx can help you navigate between copay savings cards and other discounts to save money on your prescription.
If you have commercial insurance, you may be eligible to pay as little as $30 for Xofluza using a savings card from the manufacturer. If you’re uninsured or underinsured, the same savings card can take up to $60 off the cost of your Xofluza prescription.
Frequently asked questions
Studies show that Xofluza may help you start feeling better about 8 hours faster than Tamiflu. But researchers don’t consider this difference to be statistically significant. Therefore, both medications are considered similarly effective and will help you feel better about 1 to 2 days faster than you would without taking an antiviral flu medication.
Xofluza is generally well tolerated by most people. Side effects typically happen to 3% or fewer people who take it. The most common Xofluza side effects include diarrhea and nausea. People also reported inflamed airways (bronchitis) and sinuses (sinusitis), but these are also common flu symptoms. So the medication may not be to blame for these side effects.
You should only take Xofluza if you have flu symptoms or are exposed to someone with the flu. It’s unlikely to cause harm if you take it outside of these circumstances, but it won’t offer you any benefit. And it’s unlikely a healthcare professional will prescribe it to you unless you meet one of these requirements. That’s because Xofluza doesn’t treat or prevent any illnesses other than the flu.
Studies show that Xofluza may help you start feeling better about 8 hours faster than Tamiflu. But researchers don’t consider this difference to be statistically significant. Therefore, both medications are considered similarly effective and will help you feel better about 1 to 2 days faster than you would without taking an antiviral flu medication.
Xofluza is generally well tolerated by most people. Side effects typically happen to 3% or fewer people who take it. The most common Xofluza side effects include diarrhea and nausea. People also reported inflamed airways (bronchitis) and sinuses (sinusitis), but these are also common flu symptoms. So the medication may not be to blame for these side effects.
You should only take Xofluza if you have flu symptoms or are exposed to someone with the flu. It’s unlikely to cause harm if you take it outside of these circumstances, but it won’t offer you any benefit. And it’s unlikely a healthcare professional will prescribe it to you unless you meet one of these requirements. That’s because Xofluza doesn’t treat or prevent any illnesses other than the flu.
The bottom line
Xofluza (baloxavir marboxil) treats and prevents the flu (influenza virus) in adults and children ages 5 and older. It works by blocking the flu virus from making copies of itself. This helps stop the flu infection in your body. You only need one dose of Xofluza, but you should take it within 48 hours (2 days) after your symptoms start or you’re exposed to the flu.
Xofluza starts working in about 4 hours, but it may take up to 2 days before your flu symptoms resolve. In the meantime, it’s fine to take most over-the-counter medications for flu symptoms with Xofluza if you need them.
You shouldn’t take Xofluza if you’re pregnant or breastfeeding. And you shouldn’t take more than one dose of Xofluza each time you’re exposed to or have the flu.
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References
Centers for Disease Control and Prevention. (2022). Influenza antiviral drug baloxavir marboxil.
Ren, Y., et al. (2022). Targeted inhibition of the endonuclease activity of influenza polymerase acidic proteins. Future Medicinal Chemistry.
Sportpharm doing business as Sportpharm. (2025). Xofluza- baloxavir marboxil tablet, film coated [package insert].
