To immediately treat or prevent emerging signs of the flu (influenza), healthcare providers may recommend orally administered Tamiflu, an antiviral drug approved by the Food and Drug Administration (FDA) to stop the spread of the flu virus in adults, children, and infants (2 weeks and older).

Tamiflu contains the active ingredient oseltamivir, which belongs to the neuraminidase (NA) inhibitors class.

As a prophylaxis, oseltamivir also prevents adults and children (1 year and older) exposed to the flu from getting the flu. However, antiviral drugs, including Tamiflu, are not a substitute for receiving the flu vaccine.

Tamiflu works by attacking the flu virus enzymes and keeping them from releasing new viruses in the body, reducing flu symptoms.

This article will provide an in-depth analysis of Tamiflu, exploring how it works, its potential side effects, dosing instructions, storage requirements, and other pertinent information regarding its safe use and handling.

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Understanding Flu

Symptoms of the flu are also common in other respiratory illnesses, making it difficult to diagnose. The flu is caused by the influenza virus—a respiratory infection causing symptoms ranging from mild (similar to those of the common cold) to severe and even life-threatening (such as those with pneumonia).

While many who contract the flu recover quickly, severe cases of the flu can also lead to sinus infections, ear infections, and the worsening of existing medical conditions, such as congestive heart failure (CHF) and diabetes.

Flu viruses are spread primarily by tiny droplets released when people with the flu talk, cough, or sneeze near another person. As a result, viral droplets can land in the noses or mouths of nearby people, thereby exposing them to infection.

What's more, spreading the flu to someone else is possible before you know you have it yourself.

The Centers for Disease Control and Prevention (CDC) estimates that flu has resulted in 9 million to 41 million illnesses, 140,000 to 710,000 hospitalizations, and 12,000 to 52,000 deaths annually between 2010 and 2020 in the United States.

How Does Tamiflu Work?

The active ingredient in Tamiflu is oseltamivir, which belongs to the class of drugs called NA inhibitors. NA inhibitors block the enzyme called neuraminidase produced by the flu. NA is essential in releasing and spreading new influenza viruses from infected cells.

Tamiflu is a well-tolerated orally active neuraminidase inhibitor that attacks the flu virus, stopping it from multiplying in the body and reducing flu symptoms.

How Effective Is Tamiflu?

Antiviral prescription medicines such as Tamiflu are effective in treating flu illness.

The CDC recommends prompt treatment for people with flu or suspected flu and at higher risk of severe flu complications, such as people with asthma, diabetes (including gestational diabetes), or heart disease.

Tamiflu was approved in 1999 and proved to be an effective treatment for flu. It has been shown to reduce the duration of symptoms in people with infection, reduce complications, and improve levels of prevention.

A study by the CDC confirmed that antiviral drugs for the flu reduced the length of illness and virus shedding (when the virus is replicating and reproducing) even when given two days after the onset of flu symptoms. These findings confirm the benefits of using the antiviral drug Tamiflu to treat flu-related illness.

Observational studies, per the CDC, suggest that antiviral drugs are not vaccine substitutes but can prevent severe flu complications like pneumonia.

When to Use Tamiflu

The frequency and duration of taking Tamiflu differ for treating and preventing the flu. 

Tamiflu is used for treatment after a person has been diagnosed with the flu. It has been shown to lessen the time people are sick with the flu.

In addition, Tamiflu is used as a preventive measure in people exposed to the flu, but before flu symptoms have surfaced.

Take Tamiflu twice daily (morning and evening) for five days to treat flu symptoms in adults and children aged 2 weeks and older.

When used to prevent flu, taken once a day for at least 10 days or up to six weeks during a community flu outbreak in adults and children 1 and older.

Your healthcare provider will advise you how to take Tamiflu. Take it exactly as your healthcare provider prescribes.

Who Should Avoid Tamiflu?

Tamiflu is an effective and relatively safe medicine, but it has a few limitations. In certain situations, Tamiflu is unsuitable or should be used after consulting a healthcare provider.

Do not take Tamiflu if you are allergic to oseltamivir or any Tamiflu capsules or suspension ingredients. Additionally, Tamiflu is not for use in people with end-stage renal disease (ESRD) who are not currently undergoing dialysis.

Additionally, due to its potential to exacerbate these and other conditions, call your healthcare provider if you have any condition affecting the immune system, such as human immunodeficiency virus (HIV) or AIDS, heart, lung, or kidney disease before taking Tamiflu.

The CDC recommends treating pregnant people with the flu with appropriate medication to avoid severe illness. Tamiflu is recommended for treating pregnant people with flu.

Side Effects & Safety

As with all drugs, Tamiflu may cause some side effects, which usually go away. However, at times, they can be severe and require medical observation.

Call your healthcare provider if you experience the following symptoms, if symptoms do not improve, or if they worsen.

Common Side Effects

Common side effects associated with the use of Tamiflu include:

Usually, nausea and vomiting are not severe and can be reduced by taking Tamiflu with food.

Severe Side Effects

Some side effects that follow Tamiflu usage can be severe. If you experience any of the following symptoms, call your healthcare provider immediately:

Children and teenagers with the flu may be at a greater risk for these side effects than adults.

People with untreated flu are also at risk of these side effects. Severe side effects of Tamiflu are uncommon but may result in accidental injury in some people.

Be sure to monitor yourself or a dependent closely when taking Tamiflu. Call a healthcare provider immediately if you or a loved one shows unusual or worsening symptoms.

Dosage Recommendations

Tamiflu capsules are available in 30 milligrams (mg), 45 mg, and 75 mg strengths.

Tamiflu, also available via liquid suspension (a type of medication that contains solid particles suspended in a liquid), comes in the form of a 360 mg oseltamivir suspension.

The frequency and duration of taking Tamiflu differ for treatment or prevention. Following are the recommended doses of Tamiflu:

Dosage for treatment for the flu in adolescents and adults:

  • The recommended oral dose of oseltamivir Tamiflu capsules for treating the flu in adults and adolescents 13 years and older is 75 mg twice daily.
  • Take one 75 mg capsule or 12.5 mL oral suspension twice daily for five days.

Dosage for prevention of the flu in adolescents and adults:

The recommended dosage of Tamiflu capsules for preventing the flu in people 13 and older is 75 mg orally once daily.

Take one 75 mg capsule or 12.5 mL of oral suspension once daily for:

  • At least 10 days after close contact with people with flu-related symptoms.
  • For up to six weeks during a community outbreak.
  • For 12 weeks in people with weakened immune systems

For people with renal impairment, consult your healthcare provider for dosing recommendations to treat and prevent the flu.

Dosage Guidelines: Children

The following table will show the dosage regimen of Tamiflu for children when used for the prevention and treatment of flu:

Weight: Age: Treatment Dosage for Five Days: Prophylaxis Dosage for 10 Days: The Volume of Oral Suspension (6 mg/mL) for Each Dose: Number of Capsules to Dispense (Strength);
• Any weight • Two weeks to less than 1 year of age • 3 mg/kg twice daily • N/A  • 0.5ml/kg • N/A
• 33 lbs or less • Ages 1 to 12 • 30 mg twice daily • 30 mg once daily • 5 mL •10 capsules of 30 mg
• 33 lbs to 51 lbs • Ages 1 to 12 • 45 mg twice daily • 45 mg once daily • 7.5 mL • 10 capsules of 45 mg
• 51 lbs to 88 lbs • Ages 1 to 12 • 60 mg twice daily • 60 mg once daily • 10 mL • 20 capsules of 30mg
• 89 lbs or more • Ages 1 to 12 • 75 mg twice daily • 75 mg once daily • 12.5 mL • 10 capsules of 75 mg

Storage Recommendations

For maximum efficacy and safety, keep Tamiflu in the container it came in and out of the sight and reach of pets and children.

Store the capsules at room temperature (between 68 and 77 degrees F) and away from areas susceptible to high heat and moisture levels, such as the bathroom.

The liquid suspension form of Tamiflu should be kept at room temperature for up to 10 days or in the refrigerator for up to 17 days.

Tamiflu, as a liquid suspension prepared by a pharmacist, can be kept at room temperature for up to five days or in the refrigerator for up to 35 days. Do not freeze the suspension.

Potential for Interaction

Use the following medications in consultation with your healthcare provider when taking alongside Tamiflu:

Your healthcare provider may need to change the doses of your medications or monitor carefully for side effects.


Tamiflu is a well-tolerated, orally administered NA inhibitor that reduces the duration and symptoms in people with naturally acquired flu. It is also used as a prophylactic treatment for flu.

It is an effective medicine and can be used in pregnant and breastfeeding people after consulting a healthcare provider.

Tamiflu works by inhibiting the flu virus enzyme to keep them from spreading and multiplying in the body. It helps to alleviate flu symptoms such as a stuffy nose, sore throat, cough, muscle or joint aches, tiredness, headache, fever, and chills.

However, Tamiflu and all other antiviral medications are not substitutes for flu vaccinations. The World Health Organization (WHO) and the CDC recommend a yearly flu vaccine in children 6 months and above and adults to reduce the chances of contracting (getting) the infection.

Other protective measures include limiting contact with people having flu, not going to areas with flu outbreaks, washing hands regularly, and wearing a mask.

Frequently Asked Questions

  • Is Tamiflu a substitute for the flu vaccine?

    Antiviral drugs, including Tamiflu, are not a substitute for getting a flu vaccine. A yearly flu vaccine is the best way to prevent getting and spreading seasonal flu and its potentially serious complications. Antiviral drugs are a second-line defense to prevent and treat flu.

  • What is “flu season?”

    Flu season is when flu virus outbreak and spread rates are at their maximum. According to the CDC, in the United States, flu season usually occurs in the fall and winter, starting around October.

    While the flu viruses spread year-round, flu activity peaks between December and February.

  • What other brand-name products contain oseltamivir?

    Tamiflu is the only brand name of oseltamivir approved by the FDA. In 2016, the FDA approved the first generic version of Tamiflu (oseltamivir) for treating the flu (influenza A and B).

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Ayesha Gulzar, PharmD

Ayesha Gulzar is a clinical pharmacist interested in medical research, pharmacy practice, and medication therapy management. Dr. Gulzar has been working in medical communications, writing medical and clinical research for patients and health professionals in the United Kingdom.

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