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Feeling tired: 10 medical reasons

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A serious illness can make you tired, while quite minor illnesses can leave you feeling washed out. Here are 10 health conditions known to cause fatigue.

Coeliac disease

This is a type of food intolerance, where your body reacts badly when you eat gluten – a substance found in bread, cakes and cereals.

One in 100 people in the UK are affected, but research suggests up to 70% of them don't know they have the condition, according to patient group

Coeliac UK

Other symptoms of coeliac disease, apart from tiredness, are diarrhoea, anaemia and weight loss. Your doctor can check if you have coeliac disease through a blood test.

Read more about

coeliac disease


One of the most common medical reasons for feeling constantly run down is iron deficiency anaemia.

Typically, you'll feel you can't be bothered to do anything, your muscles will feel heavy, and you'll get tired very quickly.

Women with

heavy periods
and pregnant women are especially prone to anaemia.

Read more about

iron deficiency anaemia

Chronic fatigue syndrome

Chronic fatigue syndrome (myalgic encephalomyelitis, or ME) is a severe and disabling tiredness that goes on for at least six months. There are usually other symptoms, such as a sore throat , muscle or joint pain, and headache.

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chronic fatigue syndrome

Sleep apnoea

Sleep apnoea is a condition where your throat narrows or closes during sleep and repeatedly interrupts your breathing.

This results in bad snoring and a drop in your blood's oxygen levels. The difficulty in breathing means you wake up often in the night and feel exhausted the next day.

It's most common in overweight middle-aged men. Drinking alcohol and smoking makes it worse.

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sleep apnoea

Underactive thyroid

An underactive thyroid gland means you have too little thyroid hormone (thyroxine) in your body. This makes you feel tired.

You're also likely to put on weight and have aching muscles. It's most common in women and happens more often as you get older.

Your doctor can diagnose an underactive thyroid by taking a blood test .

Read more about having an

underactive thyroid


One of the main symptoms of diabetes, a long-term condition caused by too much sugar in the blood, is feeling very tired. The other key symptoms are feeling very thirsty, going to the toilet a lot, and weight loss. Your doctor can diagnose diabetes with a blood test.

Read more about

and find out how to make smart sugar swaps.

Glandular fever

Glandular fever is a common viral infection that causes fatigue, along with fever, sore throat and swollen glands.

Most cases happen in teenagers and young adults. Symptoms usually clear up within four to six weeks, but the fatigue can linger for several more months.

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glandular fever


As well as making you feel very sad, depression can also make you feel drained of energy. It can stop you falling asleep or cause you to wake up early in the morning, which makes you feel more tired during the day.

Read more about


Restless legs

This is when you get uncomfortable sensations in your legs, which keep you awake at night.

You might have an overwhelming urge to keep moving your legs, a deep ache in your legs, or your legs might jerk spontaneously through the night.

Whatever your symptoms, your sleep will be disrupted and of poor quality, so you'll feel tired throughout the day.

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restless legs


Feeling anxious is sometimes perfectly normal. But some people have constant uncontrollable feelings of anxiety, which are so strong they affect their daily life.

Doctors call this

generalised anxiety disorder
(GAD). It affects around 5% of the UK population. As well as feeling worried and irritable, people with GAD often feel tired.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.