Tamiflu Side Effects

Generic Name: oseltamivir

Note: This page contains side effects data for the generic drug oseltamivir. It is possible that some of the dosage forms included below may not apply to the brand name Tamiflu.

It is possible that some side effects of Tamiflu may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to oseltamivir: oral capsule, oral powder for suspension

As well as its needed effects, oseltamivir (the active ingredient contained in Tamiflu) may cause unwanted side effects that require medical attention.

If any of the following side effects occur while taking oseltamivir, check with your doctor immediately:

Less common
  • Phlegm-producing cough
  • wheezing
  • Abdominal or stomach cramps or tenderness
  • arm, back, or jaw pain
  • bloating
  • chest pain or discomfort
  • diarrhea, watery and severe, which may also be bloody
  • drooling
  • facial swelling
  • fast or irregular heartbeat
  • hoarseness
  • increased thirst
  • pain
  • shortness of breath
  • unusual weight loss
Incidence not known
  • Blistering, peeling, or loosening of the skin
  • convulsions (seizures)
  • dark urine
  • difficulty with swallowing
  • fainting
  • fast, slow, or irregular heartbeat
  • hives or welts
  • itching, puffiness, or swelling of the eyelids or around the eyes, face, lips, or tongue
  • joint or muscle pain
  • light-colored stools
  • loss of bladder control
  • loss of consciousness
  • muscle spasm or jerking of all extremities
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • skin rash or itching over the entire body
  • sores, ulcers, or white spots in the mouth or on the lips
  • sweating
  • upper right abdominal or stomach pain
  • yellow eyes and skin

Some oseltamivir side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common
  • Diarrhea
  • nausea
  • vomiting
Less common
  • Abdominal or stomach pain
  • bloody nose or unexplained nosebleeds (occurs mainly in children)
  • burning, dry, or itching eyes (mainly in children)
  • dizziness
  • ear disorder (occurs mainly in children)
  • excessive tearing of the eyes (mainly in children)
  • redness, pain, or swelling of the eye or eyelid (mainly in children)
  • trouble with sleeping
  • Pale skin
  • troubled breathing
  • unusual bleeding or bruising
Incidence not known
  • blurred vision
  • cracked, dry, or scaly skin
  • dry mouth
  • flushed, dry skin
  • mood or mental changes
  • skin rash that is encrusted, scaly, and oozing

For Healthcare Professionals

Applies to oseltamivir: oral capsule, oral powder for reconstitution


The most common side effects are nausea and vomiting.

The most common side effects reported in patients receiving oseltamivir (the active ingredient contained in Tamiflu) during studies for the treatment of influenza were nausea, vomiting, bronchitis, insomnia, and vertigo. Nausea and vomiting were generally mild to moderate in severity and usually occurred on the first 2 days of treatment. Less than 1% of patients discontinued oseltamivir early due to nausea and vomiting.

Side effects in prophylaxis studies were similar to those in treatment studies. Side effects that occurred more frequently than in treatment studies were aches and pains, rhinorrhea, dyspepsia, and upper respiratory tract infections.[Ref]


Gastrointestinal side effects have been the most commonly reported and have included nausea (without vomiting; up to 10%), vomiting (up to 9%), diarrhea (up to 7%), abdominal pain (2%), and pseudomembranous colitis (less than 1%). Gastrointestinal bleeding and hemorrhagic colitis have been reported during postmarketing experience.[Ref]


Respiratory side effects have included cough (up to 5%) and bronchitis (up to 2%). The incidences were similar or higher among placebo patients and may represent symptoms of underlying influenza infection. Pneumonia has been reported (less than 1%) and may also be a symptom of underlying disease. Nasopharyngitis, congestion, rhinitis, and dry, sore throat have also been reported.[Ref]

Nervous system

Nervous system side effects have included headache (up to 18%), dizziness (up to 2%), insomnia (1%), and vertigo (up to 1%). The incidences were similar or higher among placebo patients and may represent symptoms of underlying influenza infection. Seizure has been reported during postmarketing experience.[Ref]


Psychiatric side effects have included abnormal behavior and delirium (including symptoms such as altered level of consciousness, confusion, delusions, hallucinations, agitation, anxiety, nightmares) during postmarketing experience. Mania has been reported.[Ref]

Delirium and abnormal behavior leading to injury, with fatal outcomes in some cases, in influenza patients receiving oseltamivir have been reported during postmarketing experience (mostly in Japan). Although frequency is unknown, based on oseltamivir usage, these events appear to be uncommon. These events were primarily reported in pediatric patients and often had an abrupt onset and rapid resolution. Since influenza may be associated with a variety of neurologic and behavioral symptoms (including hallucinations, delirium, and abnormal behavior, with fatal outcomes in some cases) and may occur with encephalitis or encephalopathy but can occur without obvious severe disease, oseltamivir's contribution to these effects has not been established.[Ref]


Other side effects have included fatigue (up to 8%), humerus fracture (less than 1%), pyrexia (less than 1%), and peritonsillar abscess (less than 1%). Drowsiness and malaise have been reported; however, causality has not been established. Hypothermia has been reported during postmarketing experience.[Ref]


Hematologic side effects have included anemia (less than 1%). Pancytopenia has been reported; however, causality has not been established.[Ref]


Hypersensitivity side effects have included allergy, anaphylactic/anaphylactoid reactions, and swelling of the face or tongue during postmarketing experience.[Ref]


Dermatologic side effects have included rash, dermatitis, urticaria, eczema, and serious skin reactions (including toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme) during postmarketing experience.[Ref]


Hepatic side effects have included hepatitis and abnormal liver function tests during postmarketing experience. Hepatic failure has been reported; however, causality has not been established.[Ref]


Cardiovascular side effects have included unstable angina (less than 1%). Sudden cardiopulmonary arrest has been reported; however, causality has not been established. Arrhythmia has been reported during postmarketing experience.[Ref]


Metabolic side effects have included aggravation of diabetes during postmarketing experience. Hyperglycemia has been reported; however, causality has not been established.[Ref]


Immunologic side effects have included sepsis; however, causality has not been established.[Ref]


Musculoskeletal side effects have included arthralgia in at least one patient.[Ref]


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