Not everyone with narcolepsy has the same symptoms. Some people have symptoms regularly, while others are less frequently affected.
Symptoms may develop slowly over a number of years, or suddenly over the course of a few weeks.
Narcolepsy is usually a long-term (chronic) condition, although some of the symptoms may improve as you get older.
You should see a GP if you think you may have narcolepsy so they can find out what's causing your symptoms.
If necessary, you'll be referred to a sleep disorder specialist, who can confirm the diagnosis.
Excessive daytime sleepiness is usually the first sign of narcolepsy. It can have a significant impact on everyday life.
Feeling drowsy throughout the day and struggling to stay awake makes it difficult to concentrate at work or school.
People with narcolepsy may be misjudged as being lazy or rude.
Sleep attacks, where you fall asleep suddenly and without warning, are also common in people with narcolepsy. They may happen at any time.
The length of time a sleep attack lasts will vary from person to person. Some people will only have "microsleeps" lasting a few seconds, whereas others may fall asleep for several minutes.
If narcolepsy is not well controlled, sleep attacks may happen several times a day.
Most people who have narcolepsy also experience cataplexy, which is sudden temporary muscle weakness or loss of muscular control.
Typical symptoms of cataplexy are:
Cataplexy attacks are usually triggered by an emotion, such as excitement, laughter, anger or surprise.
Attacks can last from a few seconds to several minutes.
Some people with narcolepsy have cataplexy attacks once or twice a year, while others have them several times a day.
In an attempt to avoid attacks, some people may become emotionally withdrawn and socially isolated.
Some people with narcolepsy experience episodes of sleep paralysis. This is a temporary inability to move or speak that occurs when waking up or falling asleep.
The episodes can last from a few seconds to several minutes. Although sleep paralysis does not cause any harm, being unable to move can be frightening.
Narcolepsy can also cause a number of other symptoms, including:
Speak to a GP if you have narcolepsy and it's making you feel low or depressed.
They can advise you about how to minimise the effect narcolepsy has on your daily life.
They can also put you in touch with narcolepsy organisations or support groups, such as Narcolepsy UK.