Sounds like 'oss-el-TAM-eh-veer'. Also known as Tamiflu®

Key points about oseltamivir

  • Oseltamivir is used to treat infections caused by viruses.
  • Oseltamivir is also called Tamiflu.
  • Find out how to take it safely and possible side effects.
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Oseltamivir is used to treat and prevent symptoms caused by the influenza (flu) virus. It works by stopping the influenza virus from multiplying in your body and reduces the symptoms of the flu. It also reduces the risk of other problems that can sometimes occur alongside flu, such as pneumonia. In New Zealand, oseltamivir is only funded for some people in hospital with a weakened immune system who are at higher risk of getting the complications of the flu. Others will need to pay the full cost. It is not free on prescription. Oseltamivir is available as capsules or a liquid suspension.

To treat influenza

If you already have signs and symptoms of the flu, oseltamivir helps to reduce symptoms such as fever, chills, stuffy nose, cough, sore throat, aches and tiredness. It shortens the time to recover from the flu by 12 to 24 hours.

  • Oseltamivir can reduce the chance of illnesses that may occur as a result of the flu (called complications), such as pneumonia. People at higher risk of complications include:
    • pregnant women
    • adults aged 65 years or older and residents of nursing homes
    • people with chronic disease, immunosuppression (taking medicines that weaken the immune system) or chronic respiratory condition such as asthma.
  • Oseltamivir is best started within an hour or two of the first symptoms of the flu, but it can still be effective after this time, as long as it is started within 48 hours of the first symptoms.

To prevent influenza

Oseltamivir may also be used in some high-risk people to prevent the flu if you have come into contact with someone who already has the flu (such as a sick household member) or if there is a flu outbreak in the community.

  • To prevent influenza, oseltamivir is best started within 2 days of coming into contact with someone with the flu.
  • The best way to protect against getting the flu is to get the flu vaccine every year. Oseltamivir is not a substitute for the flu vaccine.

The dose of oseltamivir is different depending on whether it is used to treat influenza or prevent influenza.

To treat influenza
  • The usual dose of oseltamivir is 75 milligrams two times a day for 5 days.
  • Oseltamivir is best started within an hour or two of the first symptoms of the flu, but it can still be effective after this time, generally within 48 hours of the first symptoms.
To prevent influenza
  • The usual dose of oseltamivir is 75 milligrams once daily for 10 days.
  • In some cases oseltamivir can be continued for up to 6 weeks during an influenza epidemic.

Always take your oseltamivir exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much oseltamivir to take, how often to take it and any special instructions.

  • Swallow your oseltamivir capsules with a glass of water.
  • You can take your oseltamivir capsules with or without food. You may take it with food or milk to reduce stomach upset.
  • If you are taking oseltamivir twice a day, space your doses evenly throughout the day. So, for example, take one dose in the morning and the other in the evening.
  • If you forget your dose, take it as soon as you remember that day. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
  • Continue to take oseltamivir for the full time it has been prescribed. Stopping the medication too early may cause a return of the infection or may not protect you from the flu.

  • Are you pregnant or breastfeeding?
  • Do you have problems with your kidneys?
  • Are you taking any other medicines? This includes any medicines you buy without a prescription, such as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start oseltamivir. Sometimes a medicine isn’t suitable for a person with certain conditions or it can only be used with extra care.

Like all medicines, oseltamivir can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Nausea (feeling sick) and vomiting (throwing up) 
  • Tummy (abdominal) pain
  • These are quite common when you first start taking oseltamivir and usually settle within 2 days
  • Try taking oseltamivir with food 
  • Tell your doctor if troublesome
  • Headache
  • Feeling tired
  • Tell your doctor if troublesome
  • Signs of an allergic reaction such as skin rash, itching, swelling of the lips, face and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

Oseltamivir patient advice (adult)(external link) NZ Formulary
Tamiflu®(external link) Medsafe Consumer Information Sheet


5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link), te reo Māori(external link)


  1. Antiviral medications for influenza(external link) Immunisation Advisory Centre, 2022
  2. Oseltamivir(external link) New Zealand Formulary

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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