Oseltamivir capsules and suspension (Tamiflu)

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Oseltamivir is used for influenza virus A and B infections.

Follow the dosing instructions carefully and remember to complete the course.

You can help prevent the virus from spreading to others by using clean tissues to cover your mouth and nose when you cough or sneeze, and by washing your hands regularly.

Remember to keep warm, drink plenty of fluids and stay away from crowds.

Type of medicineAn antiviral medicine
Used forTreating or preventing flu (influenza)
Also calledTamiflu®
Available asCapsules and oral liquid medicine (suspension)

Oseltamivir treats flu (influenza) by preventing the viruses causing the infection from spreading once they are inside your body. This reduces the symptoms of the influenza infection. It also reduces the risk of other problems which can sometimes occur alongside flu, such as pneumonia. It is most effective when it is started within an hour or two of the first symptoms of infection, but it can still be effective after this time, as long as it is started within 48 hours of the first symptoms.

Oseltamivir is also used to prevent flu when there are high numbers of people with influenza in the community, such as in epidemics and pandemics. It is used for those who have been in close contact with people with flu and for those who would be at particular risk if they developed flu (such as young children, people with long-term medical conditions, and the elderly).

Oseltamivir is not a substitute for seasonal flu vaccination.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking oseltamivir it is important that your doctor knows:

  • If you are pregnant, trying for a baby or breast-feeding. Although you can take oseltamivir if you are expecting or feeding a baby, it is important that your doctor should know about this so that you can be made aware of the benefits and any risks of treatment.
  • If you have any problems with the way your kidneys work. This is because your dose may need adjusting.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about oseltamivir and it will provide you with a full list of side-effects which you may experience from taking it.
  • Oseltamivir should be taken exactly as your doctor tells you to. This is particularly important if you are giving oseltamivir to your child, as the dose prescribed will depend upon the age of your child. Younger children are likely to be prescribed a liquid medicine. Follow the dosing instructions on the pack carefully.
  • Oseltamivir is a course of treatment. It is important that you finish the whole course (even if you do not feel unwell); otherwise the infection could return. If you have been prescribed it because you already have flu symptoms, you will need to take two doses daily for five days. Start taking it as soon as possible and space the doses evenly throughout the day. So, for example, take one dose in the morning and the other in the evening. If you are taking it because you have been in contact with someone with flu but do not have any symptoms yourself then you will be prescribed one dose a day for at least ten days. Start taking the capsules (or medicine) as soon as you collect your prescription, and from then on, take one dose a day, preferably in the morning with breakfast.
  • Swallow oseltamivir capsules with a drink of water. You can take your doses either before or after meals, although taking the doses after food can often reduce the risk of feelings of queasiness.
  • If you forget to take a dose, take it as soon as you remember (unless it is nearly time for your next dose, in which case leave out the missed dose). Do not take two doses together to make up for a forgotten dose.

How to measure the correct amount of oseltamivir liquid medicine

(Note: your pharmacist will probably have prepared the medicine for you when you collect your prescription. If this has not been done and there is only powder in the bottle, you will need to add 55 ml of water. There is a measuring cup included in the pack, which has a line on it showing how much water to use. After you have added the water, shake the bottle well to mix the water with the powder. Then, push the bottle adapter into the neck of the bottle and replace the cap.)

  1. Shake the bottle well and remove the cap.
  2. Push down the plunger of the dispenser (oral syringe) as far as it will go (so that the plunger goes down to the tip).
  3. Insert the tip of the dispenser into the adapter in the neck of the medicine bottle.
  4. Turn the bottle with the dispenser attached, upside down.
  5. Slowly pull out the plunger of the dispenser to fill it with medicine up to the mark which corresponds to the dose you need.
  6. Turn the bottle with the dispenser attached, upright again.
  7. Slowly remove the dispenser from the bottle.
  8. Put the suspension directly into your (or your child's) mouth by pushing in the plunger of the dispenser. Swallow the medicine. You can eat or drink something after swallowing the medicine if you wish.
  9. Take the dispenser apart and clean it by rinsing both parts under warm tap water.
  • The dispenser in the pack of liquid medicine measures doses up to 10 ml. If you have been given oseltamivir to give to child under 1 year of age, your doctor will give you a smaller dispenser to use which measures up to 3 ml.
  • Try to help stop the spread of flu to others. You can do this by remembering to use clean tissues to cover your mouth and nose when you cough and sneeze, binning the tissues after use, and washing your hands regularly with soap and hot water.
  • Remember to keep warm, drink plenty of fluids and stay away from crowds. If your symptoms do not improve or if they get worse, phone your doctor for further advice.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains the most common ones associated with oseltamivir. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any continue or become troublesome.

Very common oseltamivir side-effects (these affect more than 1 in 10 people)What can I do if I experience this?
Feeling or being sickThis usually passes after the first day, but you may find it helpful to take your doses after a meal
HeadacheAsk your pharmacist to recommend a suitable painkiller
Cough, blocked nose (especially in children)Ask your pharmacist to recommend a suitable remedy
Common oseltamivir side-effects (these affect less than 1 in 10 people)What can I do if I experience this?
Flu-like symptoms, difficulty sleeping, tummy ache (abdominal pain), indigestionAsk your pharmacist to recommend a suitable remedy

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • The oral liquid medicine can be stored for up to ten days after it has been made up. Do not use it after this time.
  • Store in a cool, dry place, away from direct heat and light.

If you are due to have an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr Helen Huins
Document ID:
12254 (v3)
Last Checked:
Next Review:
The Information Standard - certified member

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