Tamiflu (oseltamivir) is a prescription drug that can be used to prevent or treat influenza (the flu). The drug is available as an oral capsule or liquid suspension.
Tamiflu may be prescribed for adults and some children for the prevention or treatment of influenza (flu). It can be used for either influenza A or influenza B. It may be prescribed when you’ve been in close physical contact with someone who has the flu or if you’ve had flu symptoms for 48 hours or less.
The active ingredient in Tamiflu is oseltamivir. (An active ingredient is what makes a drug work.)
Tamiflu belongs to a group of drugs called antivirals. This article describes the dosages of Tamiflu, as well as its strengths and how to take it. To learn more about Tamiflu, see this in-depth article.
This section describes the usual dosages of Tamiflu. Keep reading to learn more.
What are Tamiflu’s forms?
Tamiflu comes in two forms that you swallow:
- a capsule
- a liquid suspension (a powder that’s mixed with water by your pharmacist)
What strengths does Tamiflu come in?
Tamiflu is available in the following strengths:
- capsules: 30 milligrams (mg), 45 mg, and 75 mg
- liquid suspension: 360 mg diluted in water to a concentration of 6 mg per milliliter (mg/mL)
What are the usual dosages of Tamiflu in adults?
The information below describes Tamiflu dosages that are commonly used or recommended for adults. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.
Dosage for treatment of influenza in adults
If you’ve had flu symptoms for no more than 48 hours, your doctor may prescribe Tamiflu. The usual dosage for treatment of the flu in adults is 75 mg of Tamiflu taken twice per day for 5 days.
Dosage for prevention of influenza in adults
If you’ve been exposed to someone with the flu in the last 48 hours, your doctor may prescribe Tamiflu as preventive therapy. The usual Tamiflu dosage for prevention of the flu in adults is 75 mg taken once daily for at least 10 days.
Your doctor may also prescribe Tamiflu when there’s been a community outbreak of influenza. A community outbreak of influenza is a spike in the number of people with the infection in your community beyond what health officials expect to see. To prevent the flu during a community outbreak, you’ll likely take 75 mg of Tamiflu once daily for up to 6 weeks. If you have a weakened immune system, your doctor may recommend that you take Tamiflu for up to 12 weeks during a community outbreak.
If you have questions about your dosage of Tamiflu, talk with your doctor or pharmacist.
What’s the dosage of Tamiflu for children?
Tamiflu may be given to some children for either the prevention or treatment of influenza. Your child’s doctor may prescribe the capsule or the liquid suspension.
The table below summarizes the recommended dosages of Tamiflu for children. Dosages depend on the age and body weight of the child and whether Tamiflu is being given for prevention or treatment of influenza. Body weight is shown in kilograms (kg). Dosages are in mg or mg per kg (mg/kg). One kg is about 2.2 pounds (lb).
| Age | Body weight | Dosage for treatment, 5 days | Dosage for prevention, 10 days* |
| 2 weeks to less than 1 year | any weight | 3 mg/kg twice per day | — |
| 1–12 years | 15 kg or less | 30 mg twice per day | 30 mg once per day |
| 1–12 years | 15.1–23 kg | 45 mg twice per day | 45 mg once per day |
| 1–12 years | 23.1–40 kg | 60 mg twice per day | 60 mg once per day |
| 1–12 years | 40.1 kg or more | 75 mg twice per day | 75 mg once per day |
| 13 years and older | any weight | 75 mg twice per day | 75 mg once per day |
* Your child will take Tamiflu for 10 days to prevent the flu following exposure to someone with the flu. But your child will take Tamiflu for up to 6–12 weeks if prescribed the medication to prevent the flu during a community outbreak.
Dosage for treatment of influenza in children
Doctors prescribe Tamiflu to children ages 2 weeks and older to treat the flu. Children prescribed Tamiflu should take it within 2 days of the start of their flu symptoms.
If your child is at least 2 weeks old but not yet 1 years old, their dose will be 3 mg/kg of Tamiflu.
And for children ages 1–12 years, depending on their body weight, the dose ranges from 30–75 mg. (You can see the above table for additional dosing details.) Your child will take their dose of Tamiflu twice per day for 5 days.
For children ages 13 years and older, the dosage is 75 mg twice per day for 5 days.
Dosage for prevention of influenza in children
For prevention of influenza, children ages 1 year and older may be prescribed Tamiflu within 48 hours of exposure to someone with the flu.
For children ages 1–12 years old, the dosage of Tamiflu to prevent the flu is based on body weight. The dose ranges from 30–75 mg and is taken once per day for 10 days. For children ages 13 years and older, the dosage is 75 mg once per day for at least 10 days.
In the event that Tamiflu is prescribed for prevention during a community outbreak of influenza, Tamiflu will be taken for up to 6–12 weeks.
For more information about Tamiflu’s dosage for children, talk with your child’s doctor or a pharmacist.
Is Tamiflu used long term?
Tamiflu is usually prescribed as a short-term treatment to treat or prevent the flu.
You’ll typically take Tamiflu for 5 days to treat the flu and for 10 days to prevent the flu. If there’s been a community outbreak, you may take Tamiflu for up to 12 weeks to prevent the flu.
If you have more questions about the length of treatment with Tamiflu, talk with your doctor or pharmacist.
Dosage adjustments
Your doctor may adjust your dosage of Tamiflu if you have kidney disease. Depending on the severity of your kidney disease, your doctor may decrease your dose, decrease your dosing frequency, or decrease both. If you’re receiving hemodialysis or peritoneal dialysis for end stage kidney disease, your doctor will also make certain dosage adjustments.
Also, if you have a weakened immune system, your doctor may recommend that you take Tamiflu for a longer time, especially if you’re taking it to prevent infection during a community outbreak of influenza.
If you have questions about how kidney disease or a weakened immune system affects your Tamiflu dosage, talk with your doctor to learn more.
The dosage of Tamiflu you’re prescribed may depend on several factors. These include:
- whether it’s being used to treat or prevent flu
- your age
- the health of your immune system*
- your kidney function*
- body weight (for children)
* See the “Dosage adjustments” section above.
Tamiflu is available as a capsule or liquid suspension.
If your doctor prescribes the capsule, you’ll swallow it whole. Don’t crush or chew the capsule.
If you or your child have trouble swallowing capsules, talk with your doctor or pharmacist about taking the liquid suspension instead. Alternatively, if the liquid suspension isn’t available at your pharmacy, they may be able to show you how to open the capsule and mix its contents with another liquid.
If you’re taking Tamiflu to treat the flu, it’s helpful to take each dose about 12 hours apart. And if you’re taking Tamiflu to prevent the flu, try to take it around the same time every day. Doing so helps to keep constant levels of Tamiflu in your body so the drug can work effectively.
Tamiflu can be taken with or without food, but taking it with food may lessen upset stomach.
You can learn more about taking the capsule or liquid suspension on the last page of Tamiflu’s prescribing information.
For information on the expiration, storage, and disposal of Tamiflu, talk with your doctor or pharmacist. You can also see the “Tamiflu expiration, storage, and disposal” section of this article.
Accessible drug containers and labels
Some pharmacies provide medication labels that:
- have large print
- use braille
- feature a code you can scan with a smartphone to change the text to audio
Your doctor or pharmacist may be able to recommend pharmacies that offer these accessibility features if your current pharmacy doesn’t.
Let your pharmacist know if you have trouble opening medication bottles. They may have tips to help, or they may be able to supply Tamiflu in an easy-open container.
If you miss a dose of Tamiflu, take it as soon as you remember. But if it’s within 2 hours of your next dose, skip the missed dose and take your next dose at its usual time. If you’re not sure whether you should take a missed dose or skip it, talk with your doctor or pharmacist.
If you need help remembering to take your dose of Tamiflu on time, try using a medication reminder. This can include setting an alarm or downloading a reminder app on your phone.
Do not take more Tamiflu than your doctor prescribes, as this can lead to harmful effects.
What to do in case you take too much Tamiflu
Call your doctor right away if you think you’ve taken too much Tamiflu. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.
Below are answers to some commonly asked questions about Tamiflu’s dosage.
Is Tamiflu’s dosage similar to Xofluza’s dosage?
Tamiflu and Xofluza (baloxavir marboxil) are both prescribed to treat or prevent influenza, but they have some differences in their dosages.
For treatment, Tamiflu is usually taken twice per day for 5 days. And for prevention, it’s usually taken once per day for 10 or more days.
On the other hand, Xofluza is taken only once as a single dose whether it’s for treatment or prevention.
Tamiflu is available as a capsule and Xofluza comes as a tablet. Both are available as liquid suspensions.
Tamiflu may be prescribed for children as young as 2 weeks old for treatment and as young as 1 year old for prevention. Xofluza is only prescribed for children ages 5 years and older for either reason. Both drugs may be prescribed to adults.
To learn more about how the dosages of Tamiflu and Xofluza compare, talk with your doctor or pharmacist.
How long does it take for Tamiflu to start working?
Tamiflu starts to work after your first dose. Studies have shown that Tamiflu decreases the number of days of flu symptoms when taken for treatment. And when used for prevention, it helped to decrease the chance of developing flu symptoms in the first place.
If you have other questions about what to expect from your Tamiflu treatment, talk with your doctor.
The sections above describe the usual dosages provided by the manufacturer. If your doctor recommends Tamiflu for you, they’ll prescribe the dosage that’s right for you.
Remember, you should not change your dosage of Tamiflu without your doctor’s recommendation. Only take Tamiflu exactly as prescribed. Talk with your doctor if you have questions or concerns about your current dosage.
Here are some examples of questions you may want to ask your doctor:
- Does my dosage of Tamiflu depend on whether I’ve had a flu shot?
- Will I need a dosage adjustment for Tamiflu if I have liver problems?
- Do I have a higher risk of experiencing side effects from Tamiflu the longer I take it?
To learn more about Tamiflu, see these articles:
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.