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Tamiflu Side Effects

Generic name: oseltamivir

Medically reviewed by Last updated on Sep 25, 2023.

Note: This document contains side effect information about oseltamivir. Some dosage forms listed on this page may not apply to the brand name Tamiflu.

Applies to oseltamivir: oral capsule, oral powder for suspension.

Serious side effects of Tamiflu

Along with its needed effects, oseltamivir (the active ingredient contained in Tamiflu) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking oseltamivir:

Less common


Incidence not known

Other side effects of Tamiflu

Some side effects of oseltamivir may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common


Incidence not known

For Healthcare Professionals

Applies to oseltamivir: oral capsule, oral powder for reconstitution.


The most common side effects were nausea and vomiting.

The most common side effects reported with this drug during studies for the treatment of influenza were nausea, vomiting, and headache; the most common side effects reported in prophylaxis studies were nausea, vomiting, headache, and pain. Most side effects were reported on a single occasion, occurred on the first or second day of therapy, and resolved spontaneously within 1 to 2 days.[Ref]

Nervous system

Very common (10% or more): Headache (up to 17%)

Common (1% to 10%): Dizziness, vertigo

Frequency not reported: Drowsiness

Postmarketing reports: Seizure/convulsion[Ref]

Side effects with similar or higher incidence among placebo patients included dizziness and vertigo.[Ref]


Very common (10% or more): Nausea

Common (1% to 10%): Vomiting, diarrhea, abdominal pain, upper abdominal pain, dyspepsia

Frequency not reported: Pseudomembranous colitis

Postmarketing reports: Gastrointestinal bleeding, hemorrhagic colitis[Ref]

Side effects with similar or higher incidence among placebo patients included diarrhea, abdominal pain, upper abdominal pain, and dyspepsia.[Ref]


Common (1% to 10%): Nasal congestion, cough, sore throat, bronchitis, nasopharyngitis, upper respiratory tract infections, influenza, rhinorrhea, sinusitis

Frequency not reported: Pneumonia, peritonsillar abscess, congestion, rhinitis, dry sore throat, epistaxis, asthma, aggravated asthma[Ref]

Side effects with similar or higher incidence among placebo patients included cough, nasal congestion, sore throat, rhinorrhea, bronchitis, sinusitis, nasopharyngitis, upper respiratory tract infections, and influenza.[Ref]


Common (1% to 10%): Insomnia

Frequency not reported: Mania

Postmarketing reports: Abnormal behavior, delirium, altered level of consciousness, confusion, delusions, hallucinations, agitation, anxiety, nightmares, self-injury[Ref]

Influenza can be associated with various neurologic and behavioral symptoms (including hallucinations, delirium, abnormal behavior), with fatal outcomes in some cases; such events may occur with encephalitis or encephalopathy but can occur without obvious severe disease. There are postmarketing reports (mostly in Japan) of delirium and abnormal behavior leading to injury, with fatal outcomes in some cases, in influenza patients using this drug. Although frequency is unknown, based on usage, these events appear uncommon. These events were primarily reported in pediatric patients, often with abrupt onset and rapid resolution. The contribution of this drug to such events has not been established.

Side effects with similar or higher incidence among placebo patients included insomnia.[Ref]


Common (1% to 10%): Fatigue, pain, pyrexia, influenza-like illness, pain in limb, otitis media, earache

Uncommon (0.1% to 1%): Tympanic membrane disorder

Frequency not reported: Humerus fracture, malaise, sepsis, facial edema, ear disorder, accidental injury

Postmarketing reports: Hypothermia[Ref]

Side effects with similar or higher incidence among placebo patients included fatigue, pyrexia, influenza-like illness, and pain in limb.[Ref]


Common (1% to 10%): Herpes simplex

Uncommon (0.1% to 1%): Dermatitis (including allergic and atopic dermatitis)

Rare (less than 0.1%): Angioneurotic edema

Postmarketing reports: Rash, urticaria, eczema, serious skin reactions, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme[Ref]

Side effects with similar or higher incidence among placebo patients included herpes simplex.[Ref]


Common (1% to 10%): Back pain, arthralgia, myalgia[Ref]

Side effects with similar or higher incidence among placebo patients included back pain, arthralgia, and myalgia.[Ref]


Common (1% to 10%): Dysmenorrhea

Side effects with similar or higher incidence among placebo patients included dysmenorrhea.


Common (1% to 10%): Conjunctivitis (including red eyes, eye discharge, eye pain)

Postmarketing reports: Visual disturbances[Ref]


Uncommon (0.1% to 1%): Elevated liver enzymes

Rare (less than 0.1%): Hepatic failure, fulminant hepatitis (including fatalities)

Frequency not reported: Hepatic function disorder, jaundice

Postmarketing reports: Hepatitis, abnormal liver function tests[Ref]


Postmarketing reports: Hypersensitivity reactions (e.g., allergic skin reactions), allergy, anaphylactic/anaphylactoid reactions, swelling of the face or tongue[Ref]


Uncommon (0.1% to 1%): Cardiac arrhythmia

Frequency not reported: Unstable angina, sudden cardiopulmonary arrest

Postmarketing reports: Arrhythmia[Ref]


Frequency not reported: Hyperglycemia

Postmarketing reports: Aggravation of diabetes[Ref]


Frequency not reported: Anemia, pancytopenia, lymphadenopathy

Postmarketing reports: Thrombocytopenia[Ref]

Frequently asked questions


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3. Cox NJ, Hughes JM. New options for the prevention of influenza. N Engl J Med. 1999;341:1387-8.

4. Treanor JJ, Hayden FG, Vrooman PS, et al. Efficacy and safety of the oral neuramidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. JAMA. 2000;283:1016-24.

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12. Snell P, Dave N, Wilson K, et al. Lack of effect of moderate hepatic impairment on the pharmacokinetics of oral oseltamivir and its metabolite oseltamivir carboxylate. Br J Clin Pharmacol. 2005;59:598-601.

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16. Cerner Multum, Inc. Australian Product Information.

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21. Antiviral drugs for influenza. Med Lett Drugs Ther. 2012;54:1-3.

22. Anekthananon T, Pukritayakamee S, Ratanasuwan W, et al. Oseltamivir and inhaled zanamivir as influenza prophylaxis in Thai health workers: a randomized, double-blind, placebo-controlled safety trial over 16 weeks. J Antimicrob Chemother. 2013;68:697-707.

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24. Cerner Multum, Inc. UK Summary of Product Characteristics.

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28. Hankey GJ. Clopidogrel and thrombotic thrombocytopenic purpura. Lancet. 2000;356:269-70.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.