Published: 00:59 BST, 30 August 2026 | Updated: 16:37 BST, 30 August 2026
Feeling tired all the time is one of the most common complaints that GPs have to deal with.
One in five Britons say they suffer from this but, for experts, it can be difficult to determine the cause.
Doctors have told The Mail on Sunday that the majority of cases can be split into 12 categories – each with their own telltale signs. But how would they define tired all the time?
‘It isn’t the same as feeling tired after a hard day’s work,’ says Dr Dean Eggitt, a Doncaster-based GP.
‘It’s fatigue that’s not supposed to be there. Fatigue you feel even after a long night’s sleep or a restful weekend. This kind of tiredness is a sign you are ill. The next question then is: why are you ill?’ Here, a team of experts reveal the reasons why you might feel tired all the time.
The most common cause of constant tiredness is depression, according to experts. The condition is typically characterised by chronic low mood, but fatigue is also a frequent symptom.
A 2016 study, which analysed data from 26 studies, showed that a fifth of patients who said they were tired all the time had depression. But a patient with depression would likely have other symptoms beyond fatigue.
‘You might expect them to have difficulty sleeping or low self-esteem,’ says Dr Eggitt.
Around half of those aged 25 to 34 report feeling exhausted – compared with only 23 per cent of those aged 55 or over
‘They might also have little desire to do the things that usually make them happy.’
Experts add that antidepressants can also trigger fatigue.
Sleep apnoea is a condition in which the throat muscles intermittently relax and collapse during sleep, blocking the airway and causing pauses in breathing. These episodes trigger snoring but they also disrupt sleep, leaving many sufferers constantly exhausted.
‘If you sleep alone, you may not realise you are snoring,’ says Dr Eggitt. ‘And if you have a partner, they might not know that snoring is caused by sleep apnoea. So many patients live with this condition for years, which can lead to fatigue.’
The most common medical treatment is a continuous positive airway pressure (CPAP) machine, a mask which uses air pressure to keep the airways open. Patients can also improve their breathing and sleep by losing weight.
