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Key takeaways
Tamiflu is a prescription antiviral drug, available in capsule and liquid versions for use in treating and preventing influenza infection.
The drug is generally safe and well tolerated, with the most common side effects being nausea and vomiting, and the risks are heightened for those with kidney problems.
Reports have associated Tamiflu with dangerous skin rashes and psychiatric symptoms, so understanding these risks and what to watch out for is paramount.
Tamiflu is a brand-name prescription drug that treats influenza A and B infections in people two weeks of age or older. It is also used to help prevent flu infections in people 1 year and older during flu season. The active ingredient in Tamiflu, oseltamivir phosphate, prevents the flu virus from producing new influenza virus particles.
Tamiflu generally has more moderate side effects and fewer drug interactions than other antiviral medications, but some people may experience problems while taking it. Even though Tamiflu is often used in acute illnesses, it is helpful to be aware of these possible problems and tips to avoid them.
RELATED: What is Tamiflu?
Common side effects of Tamiflu
Most people taking Tamiflu will not experience side effects. For those who do, unwanted side effects will be moderate and temporary, predominantly gastrointestinal problems such as nausea and vomiting. The most common Tamiflu side effects are:
- Nausea
- Vomiting
- Headache
- Stomach pain
- Fatigue
- Diaper rash (in infants ranging in age from 2 weeks to less than 1 year)
If flu symptoms get worse while taking Tamiflu, contact a healthcare professional for medical advice.
Serious side effects of Tamiflu
Serious side effects were not reported during clinical trials referred to in Tamiflu’s label, but have been reported in later use of the drug. These include:
- Abnormal behavior
- Delirium
- Self-injury
- Exacerbation of irregular heartbeat (arrhythmia)
- Anaphylaxis (a severe allergic reaction that includes trouble breathing and a dangerous drop in blood pressure)
- Severe allergic skin reactions, including erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis
Tamiflu and neuropsychiatric disorders
Tamiflu treatment has been associated with neurological and psychiatric adverse events when used to treat or prevent flu infection, particularly in children. Statistically, children in some studies were 50% more likely to have these symptoms if taking Tamiflu. Keep in mind that the risk of these symptoms is low at baseline, so the absolute increase in risk may not be substantial. While associated with Tamiflu in these studies, the symptoms were not definitively proven to be caused by the drug. The reported psychiatric symptoms have included delusions (wrong beliefs about reality), hallucinations (hearing or seeing things that aren’t there), delirium, abnormal behaviors, and self-harm, which can sometimes be fatal. Neurological symptoms include headache, convulsions, and shakiness.
These reported psychotic and behavioral events usually appeared early and suddenly when taking Tamiflu and were typically short-lived, often going away rapidly. Caregivers should carefully watch anyone taking Tamiflu for any changes in mental status, such as confusion, hallucinations, delusions, or odd behaviors, and immediately contact a healthcare provider if they are present.
Tamiflu and vomiting
Although Tamiflu has few side effects, the most commonly experienced ones are nausea and vomiting. In clinical trials listed in the drug’s label, 10% of people taking Tamiflu experienced nausea compared to 6% in the placebo group, and 8% experienced vomiting compared to 3% in the placebo group. Among children, up to 16% reported vomiting as a side effect, while 8% of those takingthe placebo had vomiting.
In most people taking Tamiflu, nausea and vomiting are not severe and typically start in the first two days of treatment. Taking Tamiflu with food or milk may decrease the likelihood or severity of these side effects.
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How soon do Tamiflu side effects start?
The timeframe for developing side effects from Tamiflu varies depending on the adverse event. Gastrointestinal effects, like nausea and vomiting, are usually experienced within the first couple of days, if at all. Reported neuropsychiatric symptoms seem to occur early on, too. On the other hand, serious skin reactions may not show up until the end of the treatment course or afterward.
How long do Tamiflu side effects last?
Most people take Tamiflu for only a few days and will experience no or only modest side effects. Most temporary side effects, including headache, nausea, and vomiting, appear early and often improve a few days after starting treatment. Some side effects, such as diaper rash in infants, may be delayed and take a few days to get better.
Severe allergic reactions, such as anaphylaxis, can have a very sudden onset, but severe skin reactions typically are delayed. Any severe allergic reaction could be life-threatening and may take days of emergency medical care to fully resolve.
Tamiflu interactions
Although Tamiflu generally has mild side effects and very few drug interactions, it still may not be right for everyone. Some people may not be able to take this medication at all, but others may need to take it cautiously and with extra monitoring. Drug interactions with Tamiflu include the following:
- Live nasal spray flu vaccines should not be given two weeks before or 48 hours after oseltamivir treatment. This could lessen the effectiveness of the vaccine.
- Clopidogrel, an antiplatelet drug that prevents blood clots, may reduce the effectiveness of Tamiflu therapy. For people taking clopidogrel, an alternative antiviral or blood thinner may be considered.
- The gout treatment drug probenecid blocks the body’s ability to break down oseltamivir, increasing the risk of side effects. A healthcare professional could advise an adjustment to the treatment plan.
Abuse and dependence
Tamiflu is not a drug that is used recreationally or that causes physical dependence. Typically, it is only prescribed for five to ten days, enough time for flu symptoms to get better. In some cases, however, it can be given for six to 12 weeks to prevent flu transmission in vulnerable populations during a community outbreak or flu pandemic. No matter how long Tamiflu is taken, discontinuing treatment does not cause withdrawal symptoms or other adverse events.
Overdose
According to the drug’s label, no side effects have been reported in the majority of people who have taken a Tamiflu overdose, but some people have experienced the drug’s common side effects when taking too high a dose. As with any prescription drug, get immediate medical help if there’s any suspicion of a Tamiflu overdose.
Contraindications
Tamiflu should never be used in patients with a known serious allergy to oseltamivir or any of the inactive ingredients in the drug.
Restrictions
Other medical conditions may require caution, extra care, or monitoring when Tamiflu is administered.
- Fructose intolerance: Because Tamiflu oral suspension contains sorbitol, people with a serious hereditary fructose intolerance should only be given Tamiflu capsules. A standard dose of Tamiflu oral suspension (75 mg) contains 2 grams of sorbitol, exceeding the daily limit for those with hereditary fructose intolerance. People with mild fructose intolerance may experience side effects such as nausea, vomiting, abdominal pain, and diarrhea.
- Kidney problems: People with moderate to severe renal impairment will be given lower doses of Tamiflu to lower the risk of side effects. Healthcare professionals are advised not to prescribe Tamiflu to anyone with end-stage renal disease unless they are undergoing dialysis.
Pregnancy and nursing
Although Tamiflu has not been shown to cause fetal problems in animals, and epidemiological data does not show an association with human birth defects, the drug has not been fully studied in pregnant women. It is not certain if it is safe to take while pregnant. It is known, however, that a flu infection can cause problems such as low birth weight, premature birth, birth defects, and even the death of the baby. Pregnant women should discuss the risks and benefits of taking Tamiflu with a healthcare provider.
The Centers for Disease Control and Prevention (CDC) strongly urges pregnant women or those planning to become pregnant to get a flu shot to prevent flu infections rather than rely on antiviral drugs such as oseltamivir.
Oseltamivir may be present in breast milk, but the amount is believed to be very low. The drug’s label states that there is no evidence of any harm to a breastfeeding baby. Both the mother and her healthcare provider will need to make a decision balancing the benefits of taking Tamiflu against any possible risks to the infant.
Children
The Food and Drug Administration (FDA) has approved oseltamivir to treat flu infections in children as young as 2 weeks old who are at a high risk for complications. It is also FDA-approved to prevent flu infections in high-risk children as young as 1 year old. Its pediatric use in children younger than these ages has not been established as safe or effective.
Seniors
Tamiflu has been shown to be as safe and effective in people older than 65 years as it is in younger adults.
Safety measures while using Tamiflu
Fortunately, Tamiflu does not have a litany of warnings associated with its use. Rarely is Tamiflu contraindicated or prohibited. However, there are instances when it may need to be avoided or adjusted.
Allergy history
Tamiflu has been associated with severe allergic skin reactions that can be life threatening. If one has a history of allergic reactions to Tamiflu, healthcare providers recommend that it not be used again.
Kidney disease
Significant reduction in kidney function can affect oseltamivir levels and consequently the risk of adverse events. Asking the Tamiflu prescriber about renal function and the appropriate drug dose is a prudent move.
Fructose intolerance
The liquid suspension of Tamiflu contains a significant amount of fructose, which could cause gastrointestinal side effects for those who are intolerant. Reminding the healthcare team about this issue can help steer them toward prescribing capsules.
How to avoid Tamiflu side effects
Most people taking Tamiflu will experience no or moderate side effects. Even so, side effects and drug interactions are possible, so a few helpful tips can help prevent or minimize problems.
1. Tell the healthcare provider about all medical conditions and medications
The first place to start in avoiding side effects is to tell the healthcare provider prescribing Tamiflu about all past and present medical conditions, especially:
- Kidney problems
- Heart problems
- Breathing problems or chronic lung disease
- Fructose intolerance
- Any condition that causes swelling or disorder of the brain
- Weakened immune system
- Pregnancy or plans to become pregnant
- Breastfeeding or plans to breastfeed
Accidental drug interactions may cause some side effects, but these are very rare. Still, healthcare professionals should be given a patient’s complete list of all prescriptions, over-the-counter medications, and dietary supplements taken before any prescription is written. In particular, a healthcare provider should be made aware of any live attenuated influenza vaccine given in the last two weeks.
2. Ask for a flu test
Tamiflu will not benefit any infection or problem other than influenza. Make sure the healthcare provider prescribing Tamiflu has clinically diagnosed influenza, has administered a flu test to verify the infection, or is prescribing a prophylactic regimen.
3. Take Tamiflu as directed
Take Tamiflu as prescribed. Read the medication guide carefully and follow the instructions on how to take a dose. The usual adult dose is 75 mg taken twice a day for five to seven days. Don’t skip a dose or take extra medicine.
4. Take Tamiflu with food
Tamiflu can be taken with a meal or on an empty stomach. To avoid nausea, vomiting, and other gastrointestinal side effects, take Tamiflu with food or milk.
5. Watch for behavior changes
Though rare, Tamiflu can be associated with changes in mental status or behavior, particularly in children. In some cases, these neurologic or psychiatric changes can be fatal. Watch closely for changes such as:
- Confusion
- Hallucinations (hearing voices or seeing things that aren’t there)
- Strange beliefs
- Unusual behaviors
- Shakiness
- Convulsions
Most of these instances have been described in the first couple of days after the initiation of Tamiflu treatment. Contact a healthcare provider immediately if they occur.
6. Watch for signs of an allergic reaction
Tamiflu can cause allergic reactions. Most, including both mild and severe allergic reactions, will affect the skin, but an anaphylactic reaction is possible, too. Watch for signs of an allergic reaction such as:
- Skin rash
- Itching
- Hives
- Blisters
- Peeling
- Swelling of the face, mouth, lips, or throat
- Trouble breathing
- Chest pain
If you notice any signs of an allergic reaction, get immediate emergency medical help. Tamiflu must be discontinued.
How to treat side effects of Tamiflu
The appropriate response to an adverse effect from Tamiflu is dependent on its nature. Mild nausea or headache may resolve without any intervention. Repeated vomiting, on the other hand, is worth talking to a healthcare professional about to see if a change or additional prescription is worthwhile. Skin rashes or psychiatric problems are reasons to get medical advice and care immediately.
Bottom line: Is Tamiflu safe?
Tamiflu is a safe drug for the vast majority of people, and that’s good news in flu season. Reducing the severity of influenza can mean less risk of hospitalization, complications, and death from this virus. While contraindications, side effects, and drug interactions can occur, they are not frequent and often can be avoided with proper planning involving healthcare providers and pharmacists.
- Oseltamivir capsules, Cleveland Clinic (2025)
- Tamiflu drug label, NIH DailyMed (2024)
- Neuraminidase inhibitors for preventing and treating influenza in adults and children, Cochrane Database of Systematic Reviews (2018)
- Tamiflu: Consumer questions and answers, FDA (2017)
- Tamiflu drug summary, Prescriber’s Digital Reference
- Treating flu with antiviral drugs, CDC (2024)