Baloxavir marboxil dosage by weight (kg): adults, children and kidney function

Baloxavir marboxil weight-based dosing table (kg)

Baloxavir marboxil dosage by condition

Treatment dose for uncomplicated influenza

The primary use of Baloxavir Marboxil is for treating uncomplicated influenza in people 5 and older. The dosage is weight-based:

• People weighing 20 kg to under 80 kg: 40 mg orally once.
• People weighing 80 kg or more: 80 mg orally once.

For children 5 and older who weigh 20 kg or more, the same weight-based dosing applies. Children 5 and older under 20 kg take 2 mg/kg as an oral suspension (liquid).

Why timing matters: take it within 48 hours

Timing is critical. Baloxavir should be taken as soon as possible after flu symptoms start, ideally within 48 hours. This early administration helps reduce the duration and severity of symptoms. Since it is a single-dose treatment, adherence is straightforward, but delaying beyond 48 hours may reduce effectiveness.

What is the typical baloxavir marboxil dose for adults?

Adults receive a single oral dose based on their body weight:

• 40 mg for those weighing 20 kg to under 80 kg.
• 80 mg for those weighing 80 kg or more.

For adults, the typical baloxavir marboxil dose is a single dose, taken once. Because it is a one-time treatment, take it only after a healthcare provider confirms the diagnosis and recommends it.

What to do if you miss a dose of baloxavir marboxil?

Contact a healthcare provider promptly for advice if you miss your baloxavir marboxil dose, since baloxavir is given as a single dose and missing it may mean the treatment opportunity is lost. This applies if you forget to take it within the recommended 48-hour window after symptom onset.

Do not take a double dose to make up for a missed one. Instead, seek guidance from a medical professional or use telehealth services like Doctronic for quick consultation. A missed or late baloxavir dose is covered in more detail in our missed-dose guide.

Pediatric dosing: ages 5 to 11 and under 20 kg

Baloxavir is approved for people 5 and older for uncomplicated flu and for post-exposure prophylaxis. For children who weigh 20 kg or more, the dosing mirrors that of adults:

• 40 mg for children weighing 20 kg to under 80 kg.
• 80 mg for children weighing 80 kg or more.

Children 5 and older who weigh under 20 kg take 2 mg/kg as an oral suspension (liquid). For children younger than 5, a prescriber can advise on other treatment options.

Post-exposure prophylaxis dose

The post-exposure prophylaxis (preventing flu after contact with someone who has it) dose of baloxavir (Xofluza) is the same single, weight-based dose used for treatment. It is for people 5 and older and is taken as soon as possible, within 48 hours of contact. It requires a prescription, and one dose is the whole course.

• 20 kg to under 80 kg: one 40 mg tablet.
• 80 kg or more: one 80 mg tablet.
• Under 20 kg (ages 5 and older): 2 mg/kg as an oral suspension (liquid).

Taking the dose later than 48 hours after contact falls outside the labeled use, so a prescriber can advise on other options.

Preventing spread is not an approved use

Giving baloxavir to a person who already has flu, to protect the people around them, is not an approved use. In the CENTERSTONE trial, one dose given to a person with flu cut the odds of passing the virus to household members by 32%. The manufacturer, Roche, has submitted these data to the FDA, but the label does not currently include this use. Household contacts who want protection can ask a prescriber about post-exposure prophylaxis for themselves. Get Xofluza prescribed online if you have had contact with someone who has flu, since the dose needs to be taken within 48 hours of that contact.

What the FDA label covers

The FDA label covers two uses in people 5 and older: treating acute uncomplicated flu, and post-exposure prophylaxis (preventing flu after contact with someone who has it) when prescribed. The safety data come from 2,079 people 5 and older across 5 controlled trials. This guide covers kilogram-based dosing, kidney and liver data, and what the trials showed.

Understanding baloxavir marboxil uses and dosages

Baloxavir Marboxil is a prescription antiviral medication designed to combat influenza by targeting the virus's replication process. It stands out because it requires only a single dose, making it convenient for patients. However, the correct dosage depends on factors such as body weight and age. Taking the right amount at the right time is crucial to maximizing effectiveness and reducing flu symptoms quickly. This guide breaks down how much Baloxavir Marboxil to take, when to take it, and what to consider for different patient groups. For crushing, food and timing questions, see our Xofluza dosing chart (patient guide). Check the name and strength on your package with a pharmacist before you take it.

Dosage forms

Baloxavir marboxil (Xofluza) comes as tablets and as granules for oral suspension (a powder mixed with water to make a liquid). Each form is a single dose, and the strength depends on your weight.

• Tablets: 40 mg and 80 mg. Each blister card holds one tablet.
• Oral suspension packets: 30 mg and 40 mg. You mix the packet in drinking water and take the whole mixture right away.
• Oral suspension bottles: 2 mg/mL. A pharmacist or healthcare provider adds 20 mL of water before dispensing, which gives 40 mg per 20 mL. Doses are measured with an oral syringe.

The suspension is meant for people who cannot swallow tablets or who need the medicine through a feeding tube. The bottle is the recommended form for anyone under 15 kg.

Dairy products, calcium-fortified drinks, antacids, laxatives containing minerals such as magnesium, and supplements with calcium, iron, magnesium, selenium, or zinc should be avoided around the time of the dose. They may keep the medicine from working as well. Strengths and packaging can change, so confirm what your pharmacy dispenses.

Renal and hepatic impairment

• Renal impairment: People with mild to moderate kidney impairment (reduced kidney function) do not need a dose adjustment. Data in severe kidney impairment are limited, so caution is advised. Anyone with severe kidney problems should check with a prescriber first, since less is known about use in that group.
• Hepatic impairment: Mild to moderate liver impairment (reduced liver function) generally does not call for a dose change. Severe liver impairment has not been extensively studied, so medical supervision is recommended. A prescriber can guide use in that group, where less is known.

Baloxavir marboxil overdose and warnings

There is limited information on overdose with Baloxavir Marboxil, but taking more than the recommended single dose is not advised. Overdose symptoms could include nausea, vomiting, or other side effects. If an overdose is suspected, seek emergency medical attention immediately. For a full picture of baloxavir marboxil side effects, see that guide.

Warnings include:

• Not a substitute for the flu vaccine.
• Post-exposure use: approved for preventing flu after contact with someone who has it (post-exposure prophylaxis) in people 5 and older, when prescribed.
• Symptoms that worsen or do not improve: consult a healthcare provider after treatment.
• Reducing spread is not an approved use.

Populations where CDC does not recommend baloxavir

CDC does not recommend baloxavir (Xofluza) during pregnancy, while breastfeeding, for hospitalized patients, or for people who are severely immunocompromised (those with a very weak immune system). CDC cites a lack of information on use in these groups so far.

• Pregnancy: The FDA label notes there are no adequate and well-controlled studies in pregnant women.
• Breastfeeding: There are no data on whether the medicine passes into human milk or how it affects a breastfed infant.
• Hospitalized patients: Hospital-level flu illness has not been well studied with this drug.
• Severely immunocompromised people: Use in this group has also not been well studied.
• Complicated or progressive illness: CDC also does not recommend it for outpatients whose flu is complicated or getting worse.

Oseltamivir is the CDC option for these groups. Flu itself raises the risk of serious complications in pregnancy, so the answer is a different antiviral, not no treatment. If you fall into one of these groups and have flu symptoms or a recent exposure, contact a prescriber promptly to discuss treatment options.

Frequently Asked Questions

Can I take Baloxavir Marboxil after 48 hours of flu symptoms?

Baloxavir is most effective when taken within 48 hours of symptom onset. Taking it later may reduce its benefits. Consult a healthcare provider for advice if you are beyond this window.

Is Baloxavir Marboxil safe for children under 12?

Baloxavir is approved for people 5 and older for uncomplicated flu and for post-exposure prophylaxis. Children younger than 5 are not covered by the label, so a prescriber can advise on other options.

Can I take Baloxavir Marboxil with other flu medications?

Always inform your healthcare provider about other medications you are taking. Some antiviral drugs may interact, so professional guidance is important.

What if I experience side effects after taking Baloxavir?

Most side effects are mild, such as diarrhea or bronchitis. If you experience severe reactions or worsening symptoms, seek medical attention promptly.

Where can I get a prescription for Baloxavir Marboxil quickly?

Telehealth services like Doctronic provide fast access to doctors who can evaluate your symptoms and prescribe Baloxavir if appropriate.

The Bottom Line

Baloxavir marboxil (Xofluza) is a single dose for uncomplicated flu in people 5 and older, and for post-exposure prophylaxis. Dosing depends on weight: 40 mg for those weighing 20 kg to under 80 kg, and 80 mg for 80 kg or more. It is most helpful when started within 48 hours of symptoms. Confirm the dose with a clinician first.