Of all Tamiflu side effects in kids, vomiting is the one the drug clearly adds: 16% on Tamiflu versus 8% on placebo in FDA label trials of children 1 to 12. Strange behavior, seizures and leg pain can be linked to the flu itself. Call the pediatrician right away about behavior changes. For rash or hives, stop Tamiflu and get medical help right away. A seizure needs emergency care.
The same label says flu itself can be linked to "hallucinations, delirium, and abnormal behavior". And in a 2025 study of about 692,000 children ages 5 to 17, the rate of serious brain and behavior events was about half as high when flu was treated with Tamiflu (oseltamivir) as when it was not.
This article is for general information only and does not replace medical advice. Consult your doctor or pharmacist for advice specific to your medications.
Get care right away for trouble breathing, bluish lips or face, a seizure, severe muscle pain (refuses to walk), no urine for 8 hours, or a child who is not alert when awake. These are CDC flu emergency warning signs in children. In an emergency, call 911.
Is It the Tamiflu or the Flu?
Tamiflu starts within 48 hours of the first flu symptoms, per the label, so the 5-day course overlaps the flu, and flu symptoms can look like side effects.
| Symptom | Drug or flu? | What to do |
|---|---|---|
| Vomiting, upset stomach | Both. More common on Tamiflu (16% vs 8%), but flu causes it too | Give doses with food or milk. Ask the pharmacist before re-dosing |
| Confusion, hallucinations, strange behavior | Reported mostly in kids on Tamiflu, but also linked to flu | Call the pediatrician right away. Watch closely |
| Seizure | The most common serious event during flu in the 2025 study | Get emergency care |
| Leg pain, won't walk | Often flu-related muscle inflammation (myositis) | Get care right away for refusing to walk or dark urine |
| Rash, hives, swelling, trouble breathing | Can be an allergic reaction to Tamiflu | Stop Tamiflu and get medical help right away |
Is Tamiflu Making Your Child Throw Up? What to Do About the Dose
In label trials of children 1 to 12, vomiting was the only side effect reported in more than 1% of kids on Tamiflu compared with placebo: 16% versus 8%. So 8 in 100 kids on a dummy medicine also threw up. The CDC notes flu can cause vomiting and diarrhea too, "more common in children than adults."
Food helps. The label says there is "less chance of stomach upset if you take TAMIFLU with food," and MedlinePlus says food or milk.
Dose came right back up? The Tamiflu label does not say whether to give another dose if a dose comes back up. So don't guess. Call your pharmacist and say how many minutes passed. Our guide for when a child throws up medicine covers what they'll ask.
Can Tamiflu Cause Hallucinations or Behavior Changes in Kids?
The FDA label on DailyMed describes reports of delirium and abnormal behavior "leading to injury, and in some cases resulting in fatal outcomes" in people with flu who were taking Tamiflu. These reports came "primarily among pediatric patients" and "often had an abrupt onset and rapid resolution."
The next line matters as much: "The contribution of TAMIFLU to these events has not been established." The label adds that flu itself can be linked to the same symptoms.
The label says to tell the doctor right away about "confusion, speech problems, shaky movements, seizures," or hearing voices or seeing things that are not really there. The label also lists nightmares, agitation and anxiety among the behavior reports.
Does Tamiflu Cause Seizures in Kids?
Seizures are on the label's list of reports after approval. But for those reports, the label says it is "not possible to reliably estimate their frequency or establish a causal relationship to TAMIFLU exposure."
A 2025 study in JAMA Neurology from Vanderbilt followed about 692,000 children ages 5 to 17 on Tennessee Medicaid through four flu seasons (2016 to 2020). It counted serious brain and behavior events that needed a hospital stay.
- The risk was lowest when children did not have the flu at all.
- Among kids with flu, treatment with Tamiflu was linked to about half the rate of serious events seen with untreated flu, after adjusting for other factors.
- The drop was mainly in neurologic events. Seizures were the most common serious event during flu.
- Among kids with flu, most events (76.7%) happened within 5 days of the flu diagnosis.
The authors concluded that treatment "was associated with a reduced risk of serious neuropsychiatric events." The flu, not the medicine, looks like the bigger risk.
Limits: it shows a link, not proof. It left out children under 5, and it missed milder events without a hospital stay.
Does Tamiflu Cause Leg Pain in Kids?
Leg pain during the flu is often the flu itself. The Tamiflu label does not list myositis or rhabdomyolysis among its side effects. The CDC lists both (muscle inflammation and muscle breakdown) as flu complications.
In kids it is called benign acute childhood myositis. A 2024 review of 22 studies found:
- Pain in both legs in 92% of affected children, often the calves.
- Fever in 80%, and 56% could not walk.
- An average age of 6.8 years.
- Influenza B was the most common virus found, then influenza A.
The review notes calf pain begins about 3 days after the fever starts. A study from the 2024 to 2025 flu season says it usually shows up as the child is recovering from the fever. That can fall in the middle of a 5-day Tamiflu course.
Recovery is fast, "around 4 days" per the review, and most kids were fully better within a week. Kidney failure was very rare in the studies it covered.
Still, the CDC lists "severe muscle pain (child refuses to walk)" as an emergency warning sign. A blood test for creatine kinase (CK), a muscle enzyme, helps confirm myositis. Go in right away for dark, red or cola-colored urine, much less urine, or weakness, which MedlinePlus lists as signs of rhabdomyolysis.
Tamiflu Side Effects in Babies and Toddlers
The label includes studies of 135 babies from 2 weeks to under 1 year old. The most reported side effects were vomiting (9%), diarrhea (7%) and diaper rash (7%). The label calls the safety profile "generally comparable" to older children and adults. For any skin rash or hives, the label's patient instructions say to stop Tamiflu and get medical help right away.
For babies under 1, MedlinePlus says to use the pharmacist's measuring device, not the manufacturer's, and never a kitchen spoon.
The CDC counts children younger than 5, "especially those younger than 2 years old," as higher risk, and recommends antivirals for higher-risk patients. For the fever, see toddler fever of 103, Tylenol or Motrin for infant fever and alternating Tylenol and Motrin.
Should You Stop Tamiflu If Your Child Has Side Effects?
Not on your own. The label says to "Take TAMIFLU exactly as your healthcare provider tells you to." The one exception is a skin or allergic reaction (rash, hives, itching, blistering, mouth sores, face or throat swelling, trouble breathing, chest pain or tightness): "Stop taking TAMIFLU and get medical help right away."
For behavior changes, call the pediatrician right away. The label tells doctors to "evaluate the risks and benefits of continuing TAMIFLU for each patient," so you decide together. For vomiting, call instead of quietly skipping doses.
Feeling better on day 3? Flu treatment is usually "two times a day (morning and evening) for 5 days," per MedlinePlus. Ask before you stop, and see stopping medication when you feel better.
If you miss a dose, the label says to give it as soon as you remember, unless it is 2 hours or less before the next dose. Never give 2 doses at the same time.
When to Call the Pediatrician About Tamiflu Side Effects in Kids
Call right away for confusion, odd behavior, speech problems, shaky movements, hallucinations, vomiting that keeps doses from staying down, or limping.
Get emergency care for the warning signs at the top of this page, or for swelling of the face or throat. The CDC adds a fever or cough that improves, then returns or worsens, a fever above 104°F that fever medicine does not bring down, and any fever in a baby younger than 12 weeks.
How Pillo Helps You Get Through a Tamiflu Course
Twice a day for 5 days is 10 doses, easy to lose track of at 2 a.m. Pillo's persistent alarm keeps ringing until you mark the dose. Spacing tips: twice-a-day medication timing.
Pillo is free for unlimited medications, with ads. Dose Notes let you jot down what happened ("threw up 10 minutes after, called pharmacist"), and the health tracker logs body temperature for the call. Dependents Management, part of Pillo's paid plan, lets you add your child as a dependent with their own schedule while the alarm rings on your phone. A log also settles whether you already gave the dose.
Frequently Asked Questions
How long do Tamiflu side effects last in kids?
For adults and teens 13 and older, the label says most reports of the common side effects in its trial table started on day 1 or 2 and cleared on their own within 1 to 2 days. Behavior reports in children "often had an abrupt onset and rapid resolution." If a side effect bothers your child or does not go away, call the pediatrician.
Should kids take Tamiflu with food?
It helps. The FDA label says Tamiflu can be taken with or without food, but there is "less chance of stomach upset" with food. MedlinePlus says food or milk.
Is Tamiflu safe for kids?
Tamiflu (oseltamivir) is recommended for flu treatment at any age by the CDC, which lists nausea, vomiting and headache as its main side effects. In a 2025 study of children 5 to 17, treated flu had about half the rate of serious brain and behavior events seen with untreated flu. The label still warns about behavior changes (call right away) and allergic reactions (stop Tamiflu and get medical help right away).
Why do pediatricians prescribe Tamiflu if it has side effects?
Early treatment can shorten fever and illness and may lower the risk of some complications, like ear infections in young children, according to the CDC. It recommends treatment for higher-risk patients, a group its flu symptoms page says includes children under 5 and people with asthma. Benefit is greatest within 48 hours.
This article is general information, not medical advice for your child. Your pediatrician and pharmacist can answer questions about every medicine your child takes.
