Flu or a cold: how to tell them apart, how long each lasts and when to get help

How do flu and a cold differ?

Colds and flu are both viral infections that affect the nose and throat, and their symptoms overlap. Flu and colds differ in how severe they are and in how quickly they start.

Flu tends to be more severe than a cold. A cold mostly affects the nose and throat, while flu can also bring a fever, aches and exhaustion.

Because the symptoms overlap, it can be hard to tell flu and a cold apart from symptoms alone. With a cold a person usually feels unwell but can manage usual activities, while flu can leave a person exhausted and too unwell to carry on as normal.

How quickly do the symptoms start?

Speed of onset is another difference the NHS pages point to. Flu tends to come on suddenly, often within hours.

A cold usually builds more gradually. The main signs of a cold are a blocked or runny nose, sneezing, a sore throat, a hoarse voice, a cough, and feeling tired and unwell.

How long do they last?

Most people start to feel better from a cold within about one to two weeks. Flu usually improves within about a week.

Tiredness can linger for longer after flu, even when the other symptoms have settled.

What treatment is there?

A cold is caused by a virus and usually gets better by itself. The NHS says the usual approach is to rest and drink fluids while the body clears the infection.

For a cold, a pharmacist can recommend suitable medicines and check which ones are suitable for the person. Antibiotics do not help, because both illnesses are caused by viruses rather than bacteria.

A flu vaccine protects against flu, but it does not protect against colds.

A pharmacist can recommend suitable cold medicines and check which ones are suitable for the person, and some are not suitable for children, pregnant women or people taking certain other medicines.

When should someone get medical help?

The NHS separates emergencies from problems that can wait for a call or an appointment.

Sudden chest pain, severe difficulty breathing or coughing up blood is an emergency, and the route is 999 or A&E.

For less urgent worries, NHS 111 or the GP can advise. The NHS says to get an urgent GP appointment or contact NHS 111 for flu symptoms with feeling very unwell, shortness of breath or no improvement.

The NHS says people aged 65 or over, people who are pregnant, and people with a long-term condition or a weakened immune system should get an urgent GP appointment or contact NHS 111 if they have flu symptoms.

The NHS says to call 999 or go to A&E for sudden chest pain, severe difficulty breathing or coughing up blood, with someone else driving or an ambulance rather than the person driving themselves.

Is it flu, a cold or something else?

Other infections can look like flu or a cold. The UKHSA publishes a guide to the signs and symptoms of flu, COVID-19 and colds, and the NHS pages for each illness set out what to look for.

Symptoms overlap, so the only way to know for sure whether a person has flu or COVID-19 is a test.

What else do the sources say?

Flu symptoms can include a sudden high temperature, an aching body and feeling exhausted. A cold usually causes a runny or blocked nose, sneezing, watery eyes and a sore throat, and does not usually bring a fever or body aches. The NHS offers the flu vaccine every year, in autumn or winter, to people at higher risk of becoming seriously ill from flu.