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Oseltamivir

Brand names: Tamiflu

Oseltamivir (Tamiflu) treats and prevents the flu. It works best when started within 2 days of symptoms.

Brand namesTamiflu
Type of medicineAntiviral (flu medicine)
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It shortens the flu by about a day and lowers complications in high-risk people. It's not a substitute for the flu shot.

What it's used for

  • Treating the flu
  • Preventing the flu after close contact

How to take it

  • Take it with food to lower nausea.
  • Finish the full course.
  • Shake the liquid well and use the measuring device.

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

  • Nausea
  • Vomiting
  • Headache
Call 911Trouble breathing, chest pain, or confusion (flu complications)
Call your provider todaySudden confusion, unusual behavior, or seeing things, especially in children
Call 911A blistering, peeling, or widespread red rash, especially with fever

Warnings

  • Watch children closely for unusual behavior while sick with flu.
  • Doses are lower with kidney disease.

Other medicines, foods, and alcohol

  • Wait 2 weeks after the nasal spray flu vaccine before taking it, or the vaccine may not work.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Recommended for pregnant people with flu because they're at high risk for complications.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember. If it's almost time for the next dose, skip the missed one. Don't double up, and still finish the full course.

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 capsules at room temperature. Keep the liquid in the refrigerator or as the label says, and throw away leftover liquid after the time on the label.

Conditions it's used for

Sources

Last updated 2026-11-13.