Baloxavir (Xofluza): Fast facts and what you need to know

Got flu symptoms and want something that works fast? Baloxavir (sold as Xofluza) is a single-dose oral antiviral that can cut how long the flu lasts when taken early. It works differently from oseltamivir — one dose targets a viral enzyme to stop the virus from multiplying. That single-dose convenience is why people ask about it first.

How and when to use baloxavir

Timing matters. Baloxavir helps most when started within 48 hours of symptom onset. It’s meant for uncomplicated seasonal flu — not for people already hospitalized with serious flu complications. If you’re high risk (older age, chronic lung or heart disease, weakened immune system, or pregnant), call your doctor quickly. They may recommend treatment but will weigh benefits and risks for your situation.

Dosing is simple for adults: a single, weight-based dose (commonly 40 mg for people 40–79 kg and 80 mg if ≥80 kg). Children have specific weight-based doses, so follow the exact instructions from a pediatrician or the drug label. Don’t try to split or modify the pill on your own.

Side effects, safety and interactions

Most people tolerate baloxavir well. Common side effects include diarrhea, nausea, and headache. Rare but serious reactions—like allergic responses or severe skin problems—can happen. If you notice trouble breathing, swelling, or a rash that spreads quickly, get medical help right away.

Drug interactions matter. Certain products that contain divalent or polyvalent cations (like calcium, magnesium, iron, or some antacids and supplements) can reduce how much baloxavir your body absorbs. Ask your pharmacist whether you should separate these products by a few hours. If you’re pregnant, breastfeeding, or on other meds, check with your provider before taking baloxavir.

Resistance can appear after use, especially in younger children, so doctors consider that when deciding treatment. That’s another reason to rely on a clinician’s advice rather than self-treating without guidance.

If symptoms worsen despite treatment—shortness of breath, chest pain, dizziness, sudden confusion, or persistent high fever—seek care immediately. Antivirals help, but they don’t remove all risk of complications.

Finally, thinking of buying baloxavir online? Use caution. Only buy from licensed pharmacies that require a prescription, show clear contact info, and have good reviews. Avoid sites offering powerful prescription drugs without asking for a prescriber’s paperwork. When in doubt, ask your doctor to recommend a trusted pharmacy or help arrange a legitimate prescription.

Baloxavir can be a handy, single-dose option for uncomplicated flu if used correctly and quickly. Talk to your healthcare provider to see if it’s right for you.