6 Tamiflu (Oseltamivir) Side Effects and How to Manage Them

If you’ve recently come down with the flu, there’s a chance a healthcare professional may have prescribed you medication to treat it. One common flu medication is Tamiflu (oseltamivir).

But what is Tamiflu, and is it safe? This antiviral medication is often the first choice when the flu strikes, since it’s considered safe for many people. Even infants and pregnant women can take Tamiflu if needed.

But as with all medications, Tamiflu can cause side effects. Most people tolerate the medication well. Still, it’s important to know what to expect should you need to take it.

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Tamiflu (oseltamivir) side effects at a glance

Most Tamiflu side effects are mild and resolve on their own after you finish taking it. In fact, many people experience no side effects from it at all.

Common Tamiflu side effects (those happening to at least 1% of people taking it) include:

• Nausea

• Vomiting

• Diarrhea

• Diaper rash in infants

• Headache

• Muscle pain

Rare but serious Tamiflu side effects include:

• Mental health changes in children

• Severe skin reactions

Below, we’ll review six of these Tamiflu side effects in more detail, plus a few other common Tamiflu questions.

1. Nausea

Nausea can happen with a lot of medications. In clinical trials, up to 10% of people ages 13 and older taking Tamiflu reported this side effect. Taking your doses with food can help lessen this feeling. Staying well hydrated, eating smaller meals, and avoiding greasy or spicy foods are also good tips for nausea relief.

2. Vomiting

For many people, Tamiflu can also cause vomiting. However, this side effect seems to be more common in children than in adolescents or adults. In studies, about 8% of people ages 13 and older taking Tamiflu reported throwing up. But this rate doubled in children between 1 year and 12 years of age. As many as 16% of them experienced vomiting.

Taking Tamiflu with food — as well as following the above tips for managing nausea — can also help prevent vomiting. But if you throw up shortly after taking it, contact your healthcare team. Depending on how long it’s been since your dose, you may need to take it again.

3. Diarrhea

Diarrhea is defined as three or more watery stools per day. And many medications list it as a side effect. Diarrhea with Tamiflu isn’t common for adults and most children. But it did happen in 7% of infants under a year old during Tamiflu’s clinical trials. About the same percentage of babies also experienced diaper rash.

Typically, loose stools caused by Tamiflu should stop after finishing the medication. But diarrhea in infants can lead to dehydration more easily than in adults. If you notice any unusual changes in your infant’s stool consistency after they start Tamiflu, contact their pediatrician.

4. Headache

Headache is another possible Tamiflu side effect. Between 2% and 17% of clinical trial participants ages 13 and older reported this side effect. It’s important to note that a similar number of people taking placebo (a pill with no medication in it) also experienced headaches during these studies. This is likely because headaches are a common symptom of the flu.

If needed, you can take over-the-counter (OTC) pain relievers to help with headaches while taking Tamiflu. Popular options include acetaminophen (Tylenol) and ibuprofen (Advil, Motrin). Neither interact with Tamiflu.

Just be careful if you’re taking them with any OTC flu medications. Many of these products already include a pain reliever in them. You may also want to ask a healthcare professional if it's safe for you to take OTC pain relievers. These medications aren’t right for everyone and come with their own unique risks and side effects.

5. Mental health changes in children

In the early 2000s, Japanese health officials reported that some children taking Tamiflu experienced mental health side effects. These included hallucinations, confusion, and behavior changes. There were also rare reports of deaths linked to these side effects.

Experts aren’t sure why this trend was seen almost exclusively in Japan. Out of caution, it’s recommended to monitor your child while they’re taking Tamiflu. If you notice any sudden changes in their mood or behavior, contact their pediatrician right away.

6. Serious skin reactions

Rarely, people taking Tamiflu have reported serious skin reactions. These reactions can be life-threatening, especially if left untreated. Examples include Stevens-Johnson syndrome and toxic epidermal necrolysis.

If you experience a rash, blisters, or skin peeling while taking Tamiflu or within 3 weeks after taking it, seek medical care. These skin reactions are considered an emergency and need immediate treatment.

Tamiflu side effects in adults vs. children

As mentioned above, some Tamiflu adverse effects are more common for certain age groups. The reason why isn’t fully understood. But it’s helpful to know which ones you or your child may be more likely to experience.

Below is a table that reviews which Tamiflu side effects are more common for adults, children, and infants.

*Young children may not be able to accurately describe this feeling. This doesn’t mean they won’t experience it.

Can you take Tamiflu while pregnant?

Yes, you can take Tamiflu during pregnancy. In fact, it’s recommended as the first-choice flu medication to take while you’re expecting. Tamiflu has the most safety data to support its use compared to other flu antivirals.

Leaving the flu untreated during pregnancy can be harmful to both you and your fetus. The risk of severe illness from the flu is higher during pregnancy. So is the risk of preterm birth (giving birth earlier than expected).

Taking Tamiflu can help lower the likelihood of these complications. But everyone’s risks during pregnancy are unique. So you should speak to your prenatal care team about the best course of action for you should you get sick with or become exposed to the flu while pregnant.

Does Tamiflu make you sleepy?

No, Tamiflu isn’t known to make you sleepy. But severe fatigue and drowsiness are common symptoms of the flu. So this feeling is more likely related to the infection. Drowsiness is also a common side effect of many OTC flu medications, such as NyQuil (acetaminophen / dextromethorphan / doxylamine).

The good news is that most people recover from the flu within 3 to 7 days. And Tamiflu can get you back on your feet about 1 to 3 days sooner than if you didn’t take any flu antivirals. So any drowsiness you feel should let up within a few days.

When should you contact your healthcare team about Tamiflu side effects?

Most Tamiflu side effects are mild. They usually subside once you’ve finished the medication. But common side effects, like headaches, are also common symptoms of the flu. So they could continue until you recover from the illness.

If any side effects become severe or too bothersome, let your healthcare team know. If you had trouble tolerating Tamiflu in the past, discuss other flu antiviral options with your prescriber.

If you experience symptoms of serious Tamiflu side effects, like severe skin reactions, seek medical help. While these side effects are rare, it’s important to treat them quickly if they happen.

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Written by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

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