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Flu - symptoms, diagnosis and treatment

Flu is an infection caused by a virus. The virus infects your lungs and upper airways.

Flu will often get better on its own, but it can make some people seriously ill. It's important to get the flu vaccine if you're advised to.

Check if you have flu

Flu symptoms come on very quickly and can include:

  • a sudden high temperature of 38 degrees or above
  • aches and pains
  • feeling tired or exhausted
  • a dry cough
  • a sore throat
  • a headache
  • difficulty sleeping
  • loss of appetite
  • diarrhoea or tummy pain
  • feeling sick and being sick

The symptoms of flu are similar for children. But they can also get a pain in their ear and seem to be less active.

Differences between cold and flu

Cold and flu symptoms are similar, but flu tends to be more severe.

Differences in symptoms between cold and flu
Cold Flu
Cold Appears gradually Flu Appears quickly within a few hours
Cold Mainly affects your nose and throat Flu Affects more than just your nose and throat
Cold Makes you feel unwell, but you can carry on as normal (for example, go to work) Flu Makes you feel exhausted and too unwell to carry on as normal

It could be COVID-19

Flu and COVID-19 can be very similar.

It could be COVID-19 if you have:

  • a high temperature
  • a new, continuous cough
  • a loss or change to your sense of smell or taste

Read about symptoms of COVID-19 and what to do.

If your symptoms do not settle, talk to your GP.

How to treat flu at home

There are some things you can do to help ease symptoms and get better more quickly.

These include:

  • get rest and sleep
  • keep warm
  • take paracetamol or ibuprofen to lower your temperature and treat aches and pains
  • drink plenty of water to avoid dehydration (your pee should be light yellow or clear)

A pharmacist can help with flu

A pharmacist can give you treatment advice and recommend flu remedies.

Avoid flu remedies that contain paracetamol if you're already taking paracetamol. Check this with your pharmacist.

Phone a pharmacy or contact them online before going in person. You can get medicines delivered or ask someone to collect them.


Antibiotics do not work for viral infections such as flu. GPs do not recommend antibiotics for flu because they will not relieve your symptoms or speed up your recovery.

When not to take antibiotics

Urgent advice: Contact your GP urgently if:

  • you're worried about your baby's or child's symptoms
  • you're 65 or older
  • you're pregnant
  • you have a long-term medical condition such as diabetes or a heart, lung, kidney or neurological disease
  • you have a weakened immune system - for example, due to chemotherapy or HIV
  • your symptoms do not improve after 7 days

Emergency action required: Call 999 or 112 or go to your emergency department (ED) if you:

  • have sudden chest pain
  • have difficulty breathing
  • start coughing up blood

Complications from flu

For some people flu can lead to more serious illness. Some complications can be life threatening.

You may need anti-viral medicines. These work best if you start taking them within 48 hours of flu symptoms.

You may be at risk of complications if you:

  • are 65 or older
  • are pregnant
  • have a long-term medical condition
  • are age 2 to 17

There are other at-risk groups.

The most common complication is pneumonia. Other complications include bronchitis and ear infections.

Flu can also cause some existing conditions to get worse.

These include:

  • asthma
  • chronic obstructive pulmonary disease (COPD)
  • heart failure

How to avoid spreading flu

Flu is very infectious and easily spread to other people. You're more likely to give it to others in the first 5 days.

The flu virus spreads through coughs and sneezes. It can live on hands and surfaces for 24 hours.

To reduce the risk of spreading flu:

  • wash your hands often with warm water and soap
  • use tissues to trap germs when you cough or sneeze
  • bin used tissues as quickly as possible

How to wash your hands correctly

How to get the flu vaccine

The flu vaccine is safe and effective. It's offered every year to help protect people at risk of flu and its complications. It is safe to get the flu vaccine during pregnancy.

The best time to get the flu vaccine is in the autumn before flu starts spreading. But you can get the vaccine any time during flu season - October to April.

Get the flu vaccine

Page last reviewed: 23 August 2023
Next review due: 23 August 2026

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.