ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.
Overview
One dose is the full treatment.
What it's used for
- Treating the flu in people 5 and older
- Preventing flu after exposure
How to take it
- Take one dose as soon as possible after symptoms start.
- Don't take it with dairy, calcium-fortified drinks, antacids, or supplements with iron, zinc, or magnesium.
Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.
Side effects
Common side effects
- Diarrhea
- Nausea
- Headache
Call 911Swelling of the face, lips, or throat, hives, or trouble breathing
Call 911Trouble breathing, chest pain, or confusion (flu getting worse)
Warnings
- Not for children under 5.
Other medicines, foods, and alcohol
- Dairy and minerals block absorption.
Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.
Pregnancy and breastfeeding
Oseltamivir is usually preferred in pregnancy.
Missed doses, overdose, and storage
If you miss a dose
Not applicable: it's a single dose.
If someone takes too much
Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.
Storing it
Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.
Conditions it's used for
Sources
- DailyMed: FDA drug label for Baloxavir (U.S. National Library of Medicine)
- MedlinePlus: Drugs, herbs, and supplements
- FDA: Drugs@FDA
Last updated 2026-11-13.