Tamiflu (Oseltamivir) – Oral

What Is Tamiflu?

Tamiflu (oseltamivir) is an antiviral medication used to treat the flu (influenza A and B). It helps to reduce symptoms and prevent the virus from multiplying in the body, giving your immune system time to get rid of it.

You can also take Tamiflu to prevent influenza infection if you have come into close contact with someone who has been diagnosed with the flu.

Tamiflu may come in capsules or oral suspension (liquid) form.

Drug Facts

Generic Name: Oseltamivir

Brand Name(s): Tamiflu

Administration Route(s): Oral

Drug Availability: Prescription

Therapeutic Classification: Antiviral

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Oseltamivir

Dosage Form(s): Capsule, oral suspension

Tamiflu (Oseltamivir) Drug Information - Illustration by Dennis Madamba

Verywell / Dennis Madamba

What Is Tamiflu Used For?

Tamiflu is used to treat or prevent illness due to influenza infection in people aged 1 year and older.

The Food and Drug Administration (FDA) approved Tamiflu for uncomplicated acute illness or prevention from influenza infection, such as:

The flu is dangerous because it can progress to pneumonia (an infection in your lungs). If you have the flu, Tamiflu works to help reduce symptoms if you start it within two days of being symptomatic. Flu symptoms can include:

  • Weakness
  • Headache
  • Fever
  • Cough
  • Runny or stuffy nose
  • Sore throat

How to Take Tamiflu

Only take Tamiflu under the direction and guidance of your healthcare provider.

Tamiflu comes in capsules and liquid suspensions, both taken by mouth. It works best when taken within 48 hours of having flu symptoms. You will usually take it twice daily for five days (treatment) or once per day for 10 days (prevention), even if symptoms improve. You can take it with or without food, but taking it with food can help prevent a stomachache.

If taking Tamiflu oral suspension, your pharmacist will give you a syringe to measure the correct dose. Use this dispenser to ensure proper dosing, rather than using household items such as spoons or cups.

It is important to note that Tamiflu is not a replacement for the flu shot. It is highly recommended to get your annual flu shot according to immunization practice guidelines for flu prevention.

Storage

Store Tamiflu capsules away from heat, moisture, and direct light and in a dry place. Do not store it in the bathroom or kitchen. Tightly close capsule containers when they are not in use and store them away from direct sunlight. You can keep the oral suspension at room temperature (up to 10 days) or in the refrigerator (up to 17 days).

Off-Label Uses

There are instances where Tamiflu may be prescribed for reasons other than what has been approved by the FDA. This is known as off-label use.

Tamiflu is sometimes used off-label to prevent or treat influenza A, avian H7N9 or H5N1.

Avian influenza is a disease caused by infection associated with avian (bird) flu type A viruses. Avian viruses occur naturally among wild birds that live on or around water, but other birds and animal species can also be infected. These flu viruses uncommonly infect humans. However, there are rare cases that have been reported.

When used for the prevention of avian influenza, Tamiflu is usually prescribed to take twice per day for five to 10 days. If the avian flu is suspected, you may be prescribed to take it even if 48 hours have passed since symptom onset for treatment.

How Long Does Tamiflu Take to Work?

Tamiflu is typically taken within 48 hours of noticing flu symptoms. When taken as prescribed, it may shorten the time you experience symptoms by a few days.

What Are the Side Effects of Tamiflu?

This is not a complete list of side effects and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist, healthcare provider, or another medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 800-FDA-1088.

Common Side Effects

Common side effects of Tamiflu may include: 

  • Diarrhea 
  • Nausea
  • Vomiting 
  • Headache

Taking Tamiflu with food can lessen the possibility of having these side effects.

Severe Side Effects

Severe side effects of Tamiflu are rare. However, some symptoms are severe and should not be taken lightly. Call your healthcare provider right away if you experience any of these side effects after taking Tamiflu:

  • Confusion 
  • Tremors 
  • Behavioral changes 
  • Seizures 
  • Signs of an allergic reaction (including itchy, red, swollen skin) 
  • Trouble breathing 
  • Hallucinations

Long-Term Side Effects

Tamiflu is generally well tolerated. However, it is intended to be taken short term when used for prevention or treatment. Your healthcare provider will let you know how long you should take it.

In the case of a community outbreak of influenza, Tamiflu is approved for use for up to six weeks in people 1 year of age and older. Follow your provider’s instructions on how much and how long to take depending on the outbreak.

Report Side Effects

Tamiflu may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Tamiflu Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage forms (capsules or suspension):
    • For treatment of the flu:
      • Adults and teenagers—75 milligrams (mg) or 12.5 milliliters (mL) two times a day (one in the morning and one in the evening) for 5 days.
      • Children 1 year of age and older—Dose is based on body weight and must be determined by your doctor. It is usually between 30 to 75 mg or 5 to 12.5 mL two times a day for 5 days.
      • Children 2 weeks of age to less than 1 year of age—Dose is based on body weight and must be determined by your doctor. It is usually 3 mg per kg of body weight two times a day for 5 days.
      • Children younger than 2 weeks of age—Use is not recommended.
    • For prevention of the flu:
      • Adults and teenagers—75 milligrams (mg) or 12.5 milliliters (mL) once a day for at least 10 days.
      • Children 1 year of age or older—Dose is based on body weight and must be determined by your doctor. It is usually between 30 to 75 mg or 5 to 12.5 mL once a day for 10 days.
      • Children younger than 1 year of age—Use is not recommended.

Modifications

In some situations, your healthcare provider may modify your treatment or change your dose.

Pregnancy

There are no adequate studies on pregnant people using this medication. So far, available data have not shown any increased risk of major birth defects following Tamiflu use during pregnancy. As with any medication, you should consult with your healthcare provider if you are pregnant or plan on becoming pregnant.

Nursing

Currently, there aren’t any studies that show whether Tamiflu is passed in human milk while nursing. Use should be under the recommendation of your provider based on risk vs. benefit.

Children

Like adults, children will benefit the most from this medication if starting it within 48 hours of symptom onset. The prescribing provider will give the medication based on the kids’ weight. The safety and efficacy of Tamiflu for the treatment of influenza have not been established in children less than 2 weeks of age. Safety and effectiveness have not been established for flu prevention in children less than 1 year.

Kidney Issues

Dose adjustments are recommended for people with kidney function status, defined by a serum creatinine clearance (CrCl) between 10 and 30 milliliters per minute (mL/min). Creatinine clearance is a measure of how the kidneys filter your blood.

Tamiflu clears from the body through the kidneys, so if your kidney is not working at full capacity, there is an increased potential for toxic levels to accumulate in the blood. 

The recommended doses for people with kidney impairment include:

  • CrCl greater than 30–60 mL/min: 30 mg twice daily
  • CrCl greater than 10–30 mL/min: 30 mg once daily

Talk to your healthcare provider for additional guidance on dosing based on kidney function.

Missed Dose

If you miss a dose, take it as soon as you think about it. If it is almost time for your next dose (within two hours), skip the missed dose and continue your regular intake schedule. Do not take extra doses or multiple doses at the same time.

Overdose: What Happens If I Take Too Much Tamiflu?

According to the FDA, there have been no reports of experiences with Tamiflu overdoses. However, taking too much (up to 1,000 mg) may cause nausea and vomiting.

What Happens If I Overdose on Tamiflu?

If you think you or someone else may have overdosed on Tamiflu, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses, has a seizure, has trouble breathing, or can’t wake up after taking too much Tamiflu, call 911 immediately.

Precautions

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It is very important that your doctor check your or your child's progress after treatment. This is to make sure that the infection is cleared up completely, and to allow your doctor to check for any unwanted effects.

This medicine is not a substitute for an annual flu shot. It also will not keep you or your child from getting a bacterial infection that starts with flu-like symptoms.

This medicine may cause a serious type of allergic reaction called anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you or your child are using this medicine.

Serious skin reactions can occur with this medicine. Stop using this medicine and check with your doctor right away if you have blistering, peeling, or loosening of the skin, red skin lesions, severe acne or skin rash, sores or ulcers on the skin, or fever or chills while you or your child are using this medicine.

Oseltamivir may cause some people, especially children and teenagers, to be agitated, irritable, or display other abnormal behaviors, which may result in injury. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.

Make sure your doctor knows if you or your child plan to get the live nasal mist flu vaccine before you start using this medicine. You should not receive the vaccine within 2 weeks before or 48 hours after using this medicine.

If your or your child's symptoms do not improve after you or your child finish taking the medicine, or if they become worse, check with your doctor.

What Are Reasons I Shouldn’t Take Tamiflu?

There are cases in which the use of Tamiflu is not recommended.

Hypersensitivity

It is not recommended to use Tamiflu if you have allergies or hypersensitivity to any components of Tamiflu. Severe allergic reactions may include anaphylaxis and serious skin reactions such as toxic epidermal necrolysis and Stevens-Johnson syndrome (rare disorder of the skin and mucous membranes).   

Other Viruses and Influenza Strains

You should not use Tamiflu to treat or prevent viruses other than influenza. You should also avoid using Tamiflu for influenza-related illnesses caused by strains that are resistant to it, meaning the medication will not be able to kill the viruses.

Interactions: What Should I Avoid?

Seizures can be a side effect of Tamiflu. People who take anti-epileptic (anti-seizure) medications should be aware that taking Tamiflu may increase their risk of having a seizure.

You should not get any live attenuated influenza vaccines (LAIV) shortly before and after taking Tamiflu. This interaction is potentially due to Tamiflu’s ability to block the replication of the live vaccine virus, which helps your body fight and kill the virus. 

It is recommended not to receive any LAIVs within two weeks before or 48 hours after taking Tamiflu unless otherwise directed by your provider.

What Medications Are Similar?

Tamiflu is a commonly used medication for the treatment and prevention of the flu. There are a few antiviral medications that can be used for influenza, including:

  • Xofluza (baloxavir marboxil) 
  • Relenza (zanamivir)
  • Rapivab (peramivir)

Xofluza (Baloxavir Marboxil)

The FDA approved the antiviral drug Xofluza in 2018 to treat the flu in people aged 12 years and older. You take Xofluza as a single dose based on body weight: 40 milligrams (mg) for those that weigh 176 pounds (80 kilograms) or less and 80 mg for those that weigh over 176 pounds.

Relenza (Zanamivir) 

Relenza is an oral inhaler medication in which two 10 mg inhalations are taken twice per day for five days to treat and prevent the flu. It is approved for use in people aged 7 years and older.

Rapivab (Peramivir) 

Rapivab is an intravenous medication that is also used to treat the flu for people aged 6 months and older. It is administered within two days of symptoms and is typically given at a single dose of 600 mg.

This list is a list of drugs also prescribed for the targeted condition(s). It is NOT a list of drugs recommended to take with Tamiflu. Some of these drugs you should not take together. Ask your pharmacist or a healthcare practitioner if you have questions.

Frequently Asked Questions

  • Is taking Tamiflu the same as taking the vaccine?

    No, it is not equivalent to getting the vaccine. The flu vaccine is the most effective way to protect yourself from the flu and prevent it from spreading to other people.

  • When can I get Tamiflu for flu prevention?

    You might be prescribed Tamiflu for flu prevention if you were exposed to or came in close contact with someone who has the flu.

  • Should I continue taking my Tamiflu medication if my flu symptoms go away?

    Even if symptoms have subsided, you should continue to take the entire course of Tamiflu as directed by your healthcare provider. Stopping your treatment too early can cause the virus to build a resistance to the medication. Your body may not be able to respond to the drug the next time you need it.

  • How do I store the oral suspension?

    Store the liquid forms of Tamiflu in the refrigerator or at room temperature. If stored at room temperature, make sure to use it within 10 days of preparation. If keeping it in the fridge, use it within 17 days of preparation.

  • What are some things I need to know or do while I take this drug?

    This drug does not treat the common cold or stop the spread of the flu to others. Please inform your healthcare provider that you are taking this medication to avoid drug interactions. The oral suspension (liquid) form contains sorbitol, which may lead to upset stomach and diarrhea in people with fructose intolerance

How Can I Stay Healthy While Taking Tamiflu?

Sticking to a medication regimen can be difficult. Try to your Tamiflu consistently to get the maximum benefits.

If you develop flu symptoms, stay home and keep your distance from other people unless you are receiving medical care. While recovering from the flu, it’s important to get lost of rest, stay well hydrated, and maintain a healthy diet.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

7 Sources
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.
  1. Food and Drug Administration. Tamiflu label.

  2. Centers for Disease Control and Prevention. 2021. Avian Influenza A Virus Infections in Humans.

  3. Beigel J, Bray M. Current and future antiviral therapy of severe seasonal and avian influenza. Antiviral Res. 2008 Apr;78(1):91-102. doi: 10.1016/j.antiviral.2008.01.003

  4. Hayden FG, Atmar RL, Schilling M, et al. Use of the selective oral neuraminidase inhibitor oseltamivir to prevent influenza. N Engl J Med. 1999 Oct 28;341(18):1336-43. doi: 10.1056/NEJM199910283411802

  5. Food and Drug Administration. Xofluza label.

  6. Food and Drug Administration. Relenza label.

  7. Food and Drug Administration. Rapivab label.