Key takeaways:
Xofluza (baloxavir marboxil) is a one-dose antiviral medication that treats and prevents the flu (influenza). You should take Xofluza within 48 hours (2 days) of coming down with flu symptoms or being exposed to the flu.
Xofluza is available as a tablet or an oral suspension (liquid). It’s usually well tolerated, but most side effects can be managed at home if they happen.
You can take Xofluza with or without food, but you should avoid foods or drinks that are high in calcium. You also shouldn’t take medications or supplements that contain calcium or metals, such as iron, zinc, or magnesium, with Xofluza.
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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If you develop flu symptoms, or you’ve been exposed to someone who has the flu (influenza), your prescriber may recommend Xofluza (baloxavir marboxil). It’s an antiviral medication that helps treat and prevent the flu in children and adults ages 5 and older.
Taking Xofluza the right way is key in order for it to work properly. Here are five pharmacist-backed tips, including when to take Xofluza, to help you get the most from your medication.
1. When to take Xofluza
You should take Xofluza within 48 hours (2 days) of the start of your flu symptoms or being exposed to someone with the flu. This means you should reach out to a healthcare professional as soon as possible for a prescription.
In some cases, your prescriber may still recommend taking Xofluza if it’s been more than 48 hours. But the medication works better the sooner you take it.
There’s no specific time of day that’s best to take Xofluza. Since it only requires one dose, most people take it as soon as they get it from their pharmacy in order to get it into their system right away. But it’s best to wait 4 to 5 hours before you take Xofluza if you’ve recently had certain foods or drinks or taken certain medications — more on that next.
2. You can take Xofluza with or without food, but avoid products high in calcium
You can take Xofluza with or without food. But taking it with food may help reduce nausea, a common Xofluza side effect.
However, it’s best to avoid foods or drinks that are high in calcium. Calcium can bind to Xofluza and keep your body from absorbing it. Examples of things to avoid include:
Dairy products (milk, yogurt, cheese)
Plant-based milks
Collard greens
Cereal fortified with calcium
Orange juice fortified with calcium
If you’ve already consumed high-calcium food products, wait 4 to 5 hours before taking Xofluza. Otherwise, avoid them until the day after you take it.
3. There are ways to manage Xofluza side effects
Xofluza is generally well tolerated. Side effects aren’t common, but may include nausea, diarrhea, and headache. Sinus pain and bronchitis are also possible, but these are also symptoms of the flu itself.
Over-the-counter (OTC) pain medications, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin), can help with headache and sinus pain if needed. Following a gentle BRAT diet (bananas, rice, applesauce, and toast) can help with diarrhea and nausea. And don’t forget to stay hydrated.
It’s also fine to take OTC cold and flu medications along with Xofluza for your symptoms, if needed. Just check the ingredients to avoid any interactions, which we’ll detail below.
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.
How does Xofluza work? Read answers to this and more common questions about Xofluza.
Most Xofluza side effects should go away on their own. But if they worsen or don’t go away, let your healthcare professional know.
4. Xofluza comes as an oral solution if you can’t swallow tablets
Xofluza comes in 40 mg and 80 mg tablets. But if swallowing a tablet is difficult for you or your child, it also comes in two different liquid forms:
An oral suspension (liquid) that contains 40 mg in each 20 mL bottle (2 mg/mL). Your pharmacy will mix this for you before dispensing it.
Packets that contain 30 mg or 40 mg of Xofluza, which are mixed with 15 mL to 20 mL of water to form a suspension. You’ll typically mix this at home on your own.
Your prescriber can specify the liquid form on your prescription if needed.
Your Xofluza dosage is based on your body weight. Follow your prescriber’s instructions carefully to make sure you take the right amount of the oral suspension for your dose. And use a measuring spoon or syringe from the pharmacy to measure it — a household spoon isn’t an accurate measuring device.
Xofluza oral suspension doesn’t require refrigeration. But you should take it within 10 hours of mixing it. If you have any medication remaining after your dose, safely discard it.
5. You shouldn’t take Xofluza with certain medications
As mentioned, calcium and certain metals can bind to Xofluza and prevent your body from absorbing it. So it’s best to avoid medications and supplements that contain any of the following ingredients:
Calcium
Zinc
Magnesium
Iron
Selenium
Aluminum
This can include certain laxatives and antacids as well as multivitamins. Supplements that help relieve cold and flu symptoms also often contain these ingredients.
If you’ve already taken one of these products, wait 4 to 5 hours before taking your Xofluza dose. Otherwise, avoid them until the day after you take it.
There are ways to save on your Xofluza prescription
Xofluza is available as a brand-name medication. If you have commercial insurance, you may be eligible to pay as little as $30 for Xofluza using a savings card from the manufacturer.
Frequently asked questions
Xofluza is unlikely to cause harm if you take it without having or being exposed to the flu. But it won’t offer you any benefit, either. 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.
Both Xofluza and Tamiflu (oseltamivir) will help you feel better about 1 to 2 days faster than you would without taking an antiviral flu medication. Studies show that Xofluza may help you start feeling better about 8 hours faster than Tamiflu. But the difference wasn’t considered clinically significant — meaning it’s likely due to chance. So both treatments are considered a similarly effective option.
Xofluza is unlikely to cause harm if you take it without having or being exposed to the flu. But it won’t offer you any benefit, either. 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.
Both Xofluza and Tamiflu (oseltamivir) will help you feel better about 1 to 2 days faster than you would without taking an antiviral flu medication. Studies show that Xofluza may help you start feeling better about 8 hours faster than Tamiflu. But the difference wasn’t considered clinically significant — meaning it’s likely due to chance. So both treatments are considered a similarly effective option.
The bottom line
Xofluza (baloxavir marboxil) is a single-dose antiviral medication that helps treat and prevent the flu (influenza). You should take Xofluza within 48 hours (2 days) of when your flu symptoms start or you’re exposed to it in order for it to work best. It comes as an oral suspension if you have trouble swallowing tablets.
You can take Xofluza with or without food, but avoid dairy products or other high-calcium food items the day you take it. It’s also best to avoid any vitamins, supplements, or medications that contain calcium or metals such as zinc, magnesium, and iron. They can make Xofluza less effective.
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References
Centers for Disease Control and Prevention. (2023). Influenza antiviral medications: Summary for clinicians.
Genentech. (2025). Xofluza- baloxavir marboxil tablet, film coated; xofluza- baloxavir marboxil granule, for solution; xofluza- baloxavir marboxil granule, for suspension [package insert].
