Key takeaways:
Tamiflu (oseltamivir) is an antiviral medication that’s a go-to choice for treating the flu. It’s generally well-tolerated with mild side effects for most people.
Common Tamiflu side effects include nausea, vomiting, and diarrhea. Nausea is more common in people ages 13 and older. Vomiting is more common for kids ages 1 to 12. And diarrhea is more common for infants under age 1.
There have been reports of children experiencing mental health issues, including hallucinations, after taking Tamiflu. But research suggests this complication may be due to the flu itself instead of the medication.
In rare cases, people have developed serious skin reactions after taking Tamiflu. These are a type of allergic reaction. If you develop a rash during or after treatment with Tamiflu, seek medical care.
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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.
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.
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.
Mild Tamiflu side effects include:
Nausea
Vomiting
Diarrhea
Stomach pain
Diaper rash in infants
Headache
Muscle pain
Rare but serious side effects and risks reported by people taking Tamiflu include:
Allergic reactions, including severe skin reactions
Confusion (delirium)
Mental health effects, such as hallucinations (seeing or hearing things that others don’t)
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, 1 out of every 10 people ages 13 and older taking Tamiflu reported this side effect.
Consider these tips to help manage nausea while taking Tamiflu:
Take your doses with food.
Stay hydrated.
Try eating several small meals a day instead of a few larger ones.
Avoid greasy, fried, and spicy foods.
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Nausea should go away after you finish taking Tamiflu. If it persists, contact your healthcare team. There may be another cause for this symptom.
2. Vomiting
For many people, Tamiflu can also cause vomiting. However, this side effect seems to be more common in children under age 13 than in adolescents or adults. Keep in mind that the flu can cause vomiting for some people (especially kids). So Tamiflu may not be the cause of this symptom.
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 with Tamiflu isn’t common for adults and most children. But it did happen frequently for infants under age 1 during Tamiflu’s clinical trials. Babies who took Tamiflu also commonly 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. It’s important to note that a similar number of people taking placebo (a pill with no medication in it) also experienced headaches during clinical trials. 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 side effects
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.
Scientists reviewed several studies to see if Tamiflu was linked to mental health side effects. Researchers found no evidence that the medication caused these symptoms. They noted that when people are very sick with the flu, it can damage cells throughout the body, including cells in the brain. So these mental health symptoms may actually be caused by the flu.
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
In rare cases, people taking Tamiflu have reported serious skin reactions. These reactions are a type of allergic reaction and 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 the weeks after taking it, seek medical care. These skin reactions are a medical 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.
Side effect | Adults and adolescents ages 13 and older | Children ages 1 to 12 years old | Infants under age 1 |
|---|---|---|---|
Nausea | More common | Not reported* | Not reported* |
Vomiting | Less common | More common | Less common |
Diarrhea | Not reported | Not reported | More common (can lead to diaper rash) |
Headache | More common | Not reported* | Not reported* |
*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.
Frequently asked questions
You’re most contagious with the flu for the first 3 days after you get sick, regardless of whether you take Tamiflu or not. Most people can still infect others for about 1 week after symptoms start. You’re likely not contagious with the flu once your symptoms have resolved and you feel back to normal. But keep in mind that some symptoms, such as coughing, can linger for a few weeks after you recover.
In most cases, you should start Tamiflu within 48 hours (2 days) of experiencing symptoms or are exposed to someone sick with the flu. But in some cases, healthcare professionals may recommend taking Tamiflu after this window passes. This is especially the case if you are very sick with the flu or are at a higher risk of flu complications, such as with older adults.
It’s unlikely that Tamiflu makes you less contagious. Studies suggest that Tamiflu doesn’t significantly lower the risk of passing the flu to others. However, the medication does help shorten the time that it takes to feel better.
To help prevent spreading the flu to others, stay home while you’re sick and try to distance yourself from those you live with as much as possible until you’re feeling better. Wearing a mask if you need to be around others is another way that can help prevent infecting others.
You’re most contagious with the flu for the first 3 days after you get sick, regardless of whether you take Tamiflu or not. Most people can still infect others for about 1 week after symptoms start. You’re likely not contagious with the flu once your symptoms have resolved and you feel back to normal. But keep in mind that some symptoms, such as coughing, can linger for a few weeks after you recover.
In most cases, you should start Tamiflu within 48 hours (2 days) of experiencing symptoms or are exposed to someone sick with the flu. But in some cases, healthcare professionals may recommend taking Tamiflu after this window passes. This is especially the case if you are very sick with the flu or are at a higher risk of flu complications, such as with older adults.
It’s unlikely that Tamiflu makes you less contagious. Studies suggest that Tamiflu doesn’t significantly lower the risk of passing the flu to others. However, the medication does help shorten the time that it takes to feel better.
To help prevent spreading the flu to others, stay home while you’re sick and try to distance yourself from those you live with as much as possible until you’re feeling better. Wearing a mask if you need to be around others is another way that can help prevent infecting others.
The bottom line
Tamiflu (oseltamivir) is a commonly prescribed flu medication. While well-tolerated, it can cause nausea, vomiting, and diarrhea for some people. Nausea is more common in people ages 13 and older. Vomiting is more common for children ages 1 to 12. And infants under age 1 are more likely to have diarrhea, which can lead to diaper rash.
Most Tamiflu side effects should go away after finishing the medication. But if you notice anything severe or out of the ordinary, contact your healthcare team. They can let you know if further care is needed.
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References
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Centers for Disease Control and Prevention. (2024). Flu & pregnancy.
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