The main symptom of myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS), is feeling extremely tired and generally unwell.

Symptoms vary from person to person, and the severity of symptoms can vary from day to day, or even within a day.

The main symptom of ME/CFS is extreme physical and mental tiredness (fatigue) that does not go away with rest or sleep. This can make it difficult to carry out everyday tasks and activities.

Most people with ME/CFS describe their fatigue as overwhelming and a different type of tiredness from what they've experienced before.

Exercising usually makes the symptoms worse. Sometimes the effect is delayed and you'll feel very tired a few hours after you've exercised, or even the next day.

Problems sleeping

Many people with ME/CFS also have problems with their sleep.

You may find that:

• you do not feel refreshed after sleeping – like you have not had a proper good night's rest
• you keep waking up during sleep
• you feel stiff, tired or have flu-like symptoms when waking up
• you feel very tired and sleepy during the day

Problems with thinking, memory and concentration

If you have ME/CFS, it's also common to have:

• problems remembering certain words, names or numbers
• difficulty concentrating or difficulty focusing on more than one thing at a time
• problems remembering things that happened recently
• being slow to speak or react to things

These problems are sometimes described "brain fog".

Other symptoms of ME/CFS can include:

• muscle or joint pain
• headaches
• a sore throat or sore glands that are not swollen
• flu-like symptoms
• feeling dizzy or sick
• fast or irregular heartbeats (heart palpitations)

Most cases of ME/CFS are mild or moderate, but 1 in 4 people have severe symptoms. If your symptoms are severe, a specialist should be involved in your treatment.

ME/CFS symptoms can be considered:

• mild – you're able to carry out everyday activities, such as work, studies or housework, but with difficulty; you may need to give up hobbies or social activities so you can rest in your spare time
• moderate – you may have difficulty moving around easily and problems carrying out daily activities; you may not be able to work or continue with your education and may need to rest often; and you may also have problems sleeping at night
• severe – you may only be able to do very basic daily tasks, such as brushing your teeth; you may be housebound or even bedbound and may need a wheelchair to get around; and you may also have difficulty concentrating, be sensitive to noise and light, and take a long time to recover after activities involving extra effort, such as leaving the house or talking for long periods
• very severe – you may have to spend all your time in bed resting and are fully dependent on carers; you may need help eating, washing and going to the toilet; you may be extremely sensitive to light and noise; you may be unable to swallow and need to be fed using a tube

There may be times when your symptoms get worse. These periods are known as relapses.

The symptoms of ME/CFS are similar to those of other conditions.

If you think you may have ME/CFS it's important to see a GP to make sure you get a correct diagnosis. A GP should also be able to refer you to a ME/CFS specialist if they think it would help you.