How Does Tamiflu Work?

Tamiflu is an antiviral prescription medication used to treat influenza type A and type B found in the human body. The generic drug is known as oseltamivir phosphate. The U.S. Food and Drug Administration says Tamiflu isn't a substitute for the flu vaccine.

A doctor is talking to a patient. (Image: Catherine Yeulet/iStock/Getty Images)

According to the FDA, side effects of Tamiflu include nausea, vomiting, headache, fatigue, insomnia, nosebleeds, confusion and allergic reactions.

Tamiflu needs to be taken as directed by your physician as there are different instructions depending on whether you already have the flu or trying to prevent it. All medication should be taken until it is gone even if symptoms dissipate.


Tamiflu works by reducing flu symptoms and by keeping the virus from replicating, according to the FDA. Symptoms of influenza include body aches, chills, fever and sore throat. It can lead to a respiratory illness such as pneumonia, which can be life threatening.

You should take Tamiflu within two days of being exposed to the virus or at the onset of flu symptoms for it to work the best. It has been approved for use by those older than 1 year of age. The FDA has also authorized use of Tamiflu for treating the H1N1 "swine flu" virus.


The FDA also says Tamiflu is used as a preventive measure against the flu. It's given to people who have been exposed to the flu or show flu-like symptoms.

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