Tamiflu side effects: diarrhea, nausea, rash and when to worry

What are the side effects of Tamiflu?

Tamiflu most often causes nausea, vomiting, and diarrhea, especially during your first few doses while your body adjusts. These symptoms are usually mild and temporary. In rare cases, more serious side effects may occur.

Tamiflu, also known as oseltamivir, is a widely prescribed antiviral medication used to treat and prevent influenza. It is ideally started within 48 hours of when flu symptoms begin. People at higher risk for flu complications should still contact a doctor about treatment if more than 48 hours have passed, and treatment started later may also help people with severe, worsening, or hospitalized illness.

Some people, particularly children, may have unusual behavior, confusion, or hallucinations. These neuropsychiatric events (changes in mood, behavior, or thinking) are uncommon, but caregivers and patients should watch for concerning changes and contact the prescriber if they arise.

Contact your doctor if you experience:

• Severe or persistent nausea, vomiting, or diarrhea
• Confusion, hallucinations, or sudden mood changes
• Severe headaches
• Any new rash (get help right away if it blisters or swells)
• Any side effect that worsens or doesn’t improve with time

For signs of an allergic reaction, such as swelling of the face or throat or trouble breathing, call emergency services right away.

If you are weighing your options, our guide to Xofluza vs Tamiflu compares these two prescription flu medications side by side.

Does Tamiflu cause diarrhea?

Yes, Tamiflu can cause diarrhea, though it is less common than nausea or vomiting. The flu itself can also cause diarrhea, so the illness may be part of the cause. This side effect is usually mild and goes away after you finish the medication.

Staying hydrated is important when you have diarrhea. Drink plenty of fluids such as water or electrolyte drinks. If diarrhea is severe or lasts longer than a few days, seek medical advice.

Tamiflu nausea and vomiting (and how long it lasts)

Nausea is the most common side effect of Tamiflu. Vomiting is common too, and in treatment trials many of these symptoms also came from the flu itself. These symptoms usually start soon after taking the medicine and can last a few days.

To reduce nausea, try taking Tamiflu with food or a full glass of water. If vomiting is severe or lasts more than a day, contact your prescriber. Sometimes, they may adjust your dose or suggest other ways to ease these symptoms.

Headache

Some people report headaches after taking Tamiflu. This side effect is generally mild and temporary. Headaches may result from your body fighting the flu or from the medication itself.

Over-the-counter pain relievers like acetaminophen can help ease headaches. If headaches become very painful or persistent, check with your doctor.

Can Tamiflu make you dizzy or tired?

Yes, Tamiflu can make some people feel dizzy or tired, though these effects were uncommon in treatment trials. Feeling tired or dizzy can also happen while your body recovers from the flu itself. These symptoms are usually not dangerous, but they can still affect your daily activities.

Rest is the best remedy. Avoid driving or operating heavy machinery if you feel dizzy. If these symptoms worsen or don’t improve, contact your doctor.

Tamiflu rash and allergic reactions

Skin rash or itching can occur with Tamiflu use. These reactions are usually mild but can sometimes signal a more serious allergic response, so check any new rash for redness, swelling, or blistering. If you notice any of these, stop the medication and get medical help immediately. Tell your prescriber about even a mild rash.

Allergic reactions to Tamiflu are rare but can be life-threatening. Signs include swelling of the face, lips, tongue, or throat, difficulty breathing, and severe rash. If you experience any of these symptoms, call emergency services right away.

People with allergies to Tamiflu or its ingredients should avoid this medication. Always tell your doctor about any known allergies before starting treatment. Also share your other medicines so they can check for Tamiflu interactions.

Behavior changes in kids and teens

Children and teens with the flu may become confused or act out of character, whether or not they take Tamiflu. The drug label says kids with influenza are at higher risk of this early in the illness. Reports of these events in people taking Tamiflu appear uncommon, and the label states that Tamiflu's role has not been established.

Watch for these changes during treatment:

• Confusion or delirium (sudden confusion and trouble knowing where they are)
• Hallucinations (seeing or hearing things that aren't there)
• Agitation, anxiety, or nightmares that are new or intense
• Unusual behavior, such as unsafe actions or sudden mood shifts

If you see any of these, call the prescriber right away. They can weigh the risks and benefits of continuing the medicine. Call emergency services if your child seems at risk of getting hurt. Stay with your child until they are evaluated.

Most children take Tamiflu without any behavior changes, and the flu itself can be dangerous. Our article on Tamiflu for kids covers dosing and safety in more detail.

Is it Tamiflu or the flu?

Often it is both, because diarrhea, nausea, headache, and fatigue are all common flu symptoms on their own. In treatment trials, nausea affected about 10% of adults and teens taking Tamiflu versus 6% on placebo, and vomiting 8% versus 3%. Placebo groups had the flu too, so much of the stomach upset comes from the illness.

A few clues can help you sort out the cause:

• Timing: Nausea that starts within hours of a dose and eases when you take it with food may point to the medicine. Stomach symptoms that began before your first dose point to the flu.
• Trend: Fever, aches, and cough improving while nausea lingers may suggest a drug effect. Everything getting worse together may suggest the flu itself.
• Headache and fatigue: Headache was reported by 2% on Tamiflu versus 1% on placebo. Both are more likely from the flu.

Flu can also cause diarrhea, especially in children.

How to ease Tamiflu side effects at home

• Take with food: Eating a small snack or a full meal before your dose can help reduce stomach upset, nausea, and vomiting. Build your dose schedule around mealtimes.
• Stay hydrated: Drink plenty of fluids to help with diarrhea and dizziness. Water, herbal teas, and electrolyte drinks all count.
• Rest and monitor symptoms: Fatigue and dizziness improve with rest, so give your body time to recover. Pay attention to how you feel and avoid strenuous activities until you are feeling better.
• Seek medical advice when needed: Call emergency services for signs of an allergic reaction. Call the prescriber right away for confusion, hallucinations, or unusual behavior. For milder symptoms that persist, your prescriber can offer guidance or discuss alternative treatments.

Frequently Asked Questions

Can Tamiflu cause side effects in children?

Yes, children can experience side effects such as nausea, vomiting, and in rare cases, neuropsychiatric symptoms. Always monitor children closely and contact a doctor if unusual behavior occurs.

Is it safe to take Tamiflu if I have allergies?

If you have known allergies to Tamiflu or its ingredients, avoid taking it. Talk to your doctor about alternative flu treatments.

How long does Tamiflu nausea last?

Usually a few days. It often starts soon after a dose. If vomiting is severe or lasts more than a day, call your prescriber.

Should I stop Tamiflu if I get diarrhea?

Mild stomach upset is not a reason to stop on your own. Call your prescriber first, since the flu itself can also cause diarrhea. Drink plenty of fluids, and seek medical advice if diarrhea is severe or lasts longer than a few days.

What does a Tamiflu rash look like?

A mild reaction may look like red, itchy skin. Redness with swelling, blistering, or a severe rash may signal a serious allergic reaction. Stop the medication and get medical help right away if you notice these signs.

The Bottom Line

Most people tolerate Tamiflu well, especially when they take it with food. Watch children for behavior changes and call the prescriber if you see any. Trouble breathing or a severe rash needs emergency care right away.