Pronunciation: TAM-ih-flew
Generic name: oseltamivir
Dosage form: oral capsules, powder for oral suspension
Drug class: Neuraminidase inhibitors

Medically reviewed by Carmen Pope, Senior Medical Editor, B. Pharm. Last updated on Aug 12, 2026.

What is Tamiflu?

Tamiflu is an antiviral medication that blocks the actions of influenza virus types A and B in your body.

Tamiflu is used to treat flu symptoms caused by the influenza virus in people 2 weeks of age and older who have had symptoms for no more than 2 days. This medicine is also used to prevent influenza in people 1 year of age and older who may be exposed but do not yet have symptoms. Tamiflu will not treat the common cold.

It is not known if Tamiflu is effective in people who start treatment more than 2 days after flu symptoms begin. It is also not known if Tamiflu is effective for treating the flu in people with long-term (chronic) heart or breathing problems, or for treating or preventing the flu in people who have weakened immune systems.

Tamiflu should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Tamiflu (oseltamivir) first received FDA approval on October 27, 1999. A generic Tamiflu, available in capsule and liquid suspension forms, is available under the name oseltamivir.

What are the possible side effects of Tamiflu?

Serious side effects

Tamiflu may cause serious side effects, including:

• Serious skin and allergic reactions. Tamiflu can cause serious skin and allergic reactions. Stop taking Tamiflu and get medical help right away if you get any of the following symptoms:
  • skin rash or hives
  • your skin blisters and peels
  • swelling of your face, eyes, lips, tongue, or throat
  • trouble breathing
  • blisters or sores in your mouth
  • chest pain or tightness
  • itching.
• Changes in behavior. People, especially children, who have the flu can develop nervous system problems and abnormal behavior that can lead to death. During treatment with Tamiflu, tell your healthcare provider right away if you or your child have confusion, speech problems, shaky movements, seizures, or start hearing voices or seeing things that are not really there (hallucinations).

Common side effects

The most common side effects of Tamiflu when used for treatment of the flu include nausea, vomiting, and headache.

The most common side effects of Tamiflu when used for prevention of the flu include nausea, vomiting, headache, and pain.

Tell your healthcare provider if you have any side effect that bothers you or that does not go away.

These are not all of the possible side effects of Tamiflu. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Before taking this medicine

You should not use Tamiflu if you are allergic to oseltamivir.

Do not use Tamiflu to treat flu symptoms in a child younger than 2 weeks old. Children as young as 1 year old may use this medicine to prevent flu symptoms.

Tell your doctor if you have ever had:

• trouble swallowing capsules;
• kidney disease (or if you are on dialysis);
• heart disease or chronic lung disease;
• a condition causing swelling or disorder of the brain;
• a weak immune system (caused by disease or by using certain medicine);
• hereditary fructose intolerance. Tamiflu oral suspension contains sorbitol and may cause stomach upset and diarrhea in people who are fructose intolerant; or
• if you have used a nasal flu vaccine (FluMist) within the past 2 weeks.

Tamiflu is not recommended for people with end-stage renal disease (ESRD) who are not receiving dialysis.

Tamiflu does not treat or prevent illness caused by infections other than the influenza virus, and it does not prevent bacterial infections that may happen with the flu.

Pregnancy and breastfeeding

Available data from published studies suggest that oseltamivir, taken during any trimester, is not associated with an increased risk of birth defects. Getting sick with influenza during pregnancy can cause complications leading to low birth weight, preterm delivery, or stillbirth. Your doctor will decide whether you should receive oseltamivir if you are pregnant.

The Centers for Disease Control and Prevention (CDC) recommends that pregnant women receive a yearly flu vaccine to prevent influenza. Oseltamivir is not to be used in place of the yearly flu shot.

Oseltamivir and its active form can pass into breast milk in small amounts, at levels considered unlikely to harm a nursing baby. Tell your doctor if you are breastfeeding a baby.

How should I take Tamiflu? 

Take Tamiflu for as many days as it has been prescribed for you, even if you begin to feel better. Your symptoms may start to improve before the infection is completely treated. Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Start taking Tamiflu as soon as possible after flu symptoms appear, such as fever, chills, muscle aches, sore throat, and runny or stuffy nose.

• Take the capsule with a full glass of water.
• Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).
• Tamiflu may be taken with food if it upsets your stomach.

To treat flu symptoms: Take Tamiflu every 12 hours for 5 days.

To prevent flu symptoms: Take Tamiflu every 24 hours for 10 days or as prescribed. Follow your doctor's instructions.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Tell your doctor if your symptoms do not improve, or if they get worse.

What happens if I miss a dose?

Use the medicine as soon as you can, but skip the missed dose if your next dose is due in less than 2 hours. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What to avoid

Do not use a nasal flu vaccine (FluMist) within 48 hours after taking Tamiflu. Oseltamivir may interfere with the drug action of FluMist, making the vaccine less effective. Follow your doctor's instructions.

Related/similar drugs

What other drugs will affect Tamiflu?

Other drugs may interact with oseltamivir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Avoid the nasal spray flu vaccine (FluMist) in the 2 weeks before or the 48 hours after taking Tamiflu, since the medicine can make this vaccine work less well. Your doctor may make an exception if needed.

No dose adjustments are needed for either oseltamivir or the other medicine when it is taken with amoxicillin, acetaminophen, aspirin, cimetidine, antacids (magnesium and aluminum hydroxides and calcium carbonates), rimantadine, amantadine, or warfarin.

Storage

Store capsules at room temperature between 68°F and 77°F (20°C to 25°C), away from moisture and heat.

Store the oral suspension in the refrigerator for up to 17 days, between 36°F and 46°F (2°C to 8°C). Do not freeze. The liquid may also be stored at room temperature, between 68°F and 77°F (20°C to 25°C), for up to 10 days. Throw away any unused liquid after the storage time has passed.

What are the ingredients in Tamiflu?

Active ingredient: oseltamivir phosphate

Inactive ingredients:

• Tamiflu capsules: croscarmellose sodium, povidone K30, pregelatinized starch, sodium stearyl fumarate, and talc 30 mg capsule shell: gelatin, red iron oxide, titanium dioxide, and yellow iron oxide 45 mg capsules shell: black iron oxide, gelatin, and titanium dioxide 75 mg capsules shell: black iron oxide, gelatin, red iron oxide, titanium dioxide, and yellow iron oxide
• Tamiflu for oral suspension: monosodium citrate, saccharin sodium, sodium benzoate, sorbitol, titanium dioxide, tutti-frutti flavoring, and xanthan gum.

Available as oral capsules (30 mg, 45 mg, 75 mg)  and a powder for oral suspension (360 mg oseltamivir base supplied as powder and constituted to a final concentration of 6 mg/mL).

Company

Tamiflu (oseltamivir) is distributed by Genentech, Inc., A Member of the Roche Group, 1 DNA Way, South San Francisco, CA 94080-4990. 

Common questions about Tamiflu

More FAQ

• Does Tamiflu (oseltamivir) work on COVID-19?
• Can I drink alcohol if I'm taking Tamiflu?
• What is the difference between Xofluza and Tamiflu?

Further information

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

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