Key takeaways

  • Tamiflu (oseltamivir) is an antiviral medication used to treat influenza in people ages 2 weeks and older and help prevent the flu in people ages 1 year and older.
  • Common side effects include headache, nausea, and vomiting. Taking Tamiflu with food may help reduce nausea and stomach upset.
  • Serious side effects can include mental health changes such as delirium, hallucinations, or confusion, especially in children.

Tamiflu comes as an oral capsule and an oral liquid suspension (a powder mixed with liquid by your pharmacist).

Keep reading to learn about common, mild, and serious side effects Tamiflu can cause.

More commonly reported side effects of Tamiflu include:

  • headache
  • nausea (see “Tips for managing side effects”)
  • vomiting

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Tamiflu unless your doctor recommends it.

Experiencing side effects? After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking this drug and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Other possible side effects of Tamiflu include:

  • general body pain
  • mental health changes (see “Tips for managing side effects”)

For some people, Tamiflu can cause an allergic reaction. This wasn’t a side effect seen in Tamiflu’s studies, but it has been reported since the drug came on the market.

If you develop serious side effects while taking Tamiflu, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

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Get answers to some frequently asked questions about Tamiflu’s side effects.

No, Tamiflu isn’t an antibiotic. Tamiflu is used to treat influenza, which is a virus, so it’s considered an antiviral medication.

Yes. The safety and effectiveness of Tamiflu were no different in adults ages 65 years and older than in younger people in the drug’s studies. Talk with your doctor if you have concerns about taking Tamiflu due to your age.

Side effects were similar in children and adults in Tamiflu studies.

In children ages 1 to 12 years, vomiting was the only side effect commonly reported. Tamiflu was taken for both influenza treatment and prevention in these children. Vomiting was also a common side effect reported by adults taking Tamiflu for the treatment and prevention of influenza.

In children ages 2 weeks to 1 year, vomiting, diarrhea, and diaper rash were commonly reported side effects. These children were taking Tamiflu for influenza treatment.

Tamiflu can sometimes cause harmful effects in people with certain conditions. Talk with your doctor about your health history before taking this drug. Be sure to tell them if any of the following factors apply to you:

Learn more about some of the side effects Tamiflu may cause.

Mental health changes

Mental health changes are serious side effects that can occur from taking Tamiflu. Mental health changes weren’t seen in the drug’s studies, but have been reported since Tamiflu was approved for use.

These changes—which often started suddenly and resolved quickly—were more commonly reported in children. It’s unclear how often this has happened or if Tamiflu was the cause, but such mental health changes can lead to injury and death.

Mental health changes may cause symptoms such as:

What might help

Talk with your doctor right away if you or your child develops any of the above symptoms while taking Tamiflu.

Nausea

Nausea was a common side effect reported in studies of Tamiflu. Nausea may cause symptoms such as stomach discomfort and a desire to vomit.

What might help

Taking Tamiflu with food may reduce your risk of nausea and upset stomach. If your symptoms are ongoing or bothersome, talk with your doctor. They can provide recommendations to help manage this side effect.

Reflection time: Have you noticed patterns in when side effects tend to feel more noticeable?

Like most drugs, Tamiflu can cause side effects that range from mild to serious.

Talk with your doctor if you have questions about what to expect when taking Tamiflu.

Disclaimer: While Healthline strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.