Skip to main content

We use cookies to help us improve your experience and to provide services like web chat. We also use cookies to measure the effectiveness of public health campaigns and understand how people use the website.

To find out more about cookies and how we use them, please see our privacy policy.

Flu - symptoms and diagnosis

Flu (influenza) is a severe infection caused by a virus. 

Usually, you don’t need to see your GP. Most flu can be treated at home. Antibiotics do not work on flu. Getting lots of rest and drinking plenty of liquids will make you feel better.

Most people who think they have the flu usually just have a cold.

The real flu is not that common and tends to happen during the winter. It usually spreads between November and March.

If you are at risk of the complications of flu, you should see your GP. You may need special anti-viral medicines. These work best if started within 48 hours of flu symptoms.

Symptoms

Flu symptoms come on very quickly and you get severe muscle aches and a high fever. Headache is very common. You will feel extremely weak and may find it hard to even get out of bed. After a few days, you may develop a cough. The flu virus infects your lungs and upper airways.

Flu symptoms can also include:

  • sore throat
  • difficulty sleeping
  • loss of appetite
  • diarrhoea or tummy pain
  • nausea and vomiting

The symptoms are similar for children. But they can also get pain in their ear and are less active.

Diagnosis

Most people who think they have the flu usually only have a cold.

The real flu is not that common and tends to happen during the winter. It may begin any time from November to March.

It is useful to know the difference between a cold and the flu.

Flu symptoms:

  • come on suddenly
  • starts with a fever, muscle aches, headache and fatigue

Cold symptoms:

  • usually comes on gradually
  • starts with a sore throat and a blocked or a runny nose.

Symptoms of a cold are generally mild compared to flu.

Complications

For most people, flu is just a bad experience. But for others, it can lead to more serious illness.

The most common complication is pneumonia. Flu can also worsen existing conditions such as:

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

If you are pregnant, or if you are on medication that may have weakened your immune system, you have an increased risk of complications from the flu. You may need special anti-viral medicines. These work best if started within 48 hours of flu symptoms.

Page last reviewed: 13/06/2019
Next review due: 13/06/2022