Feeling tired now and then is a normal part of life, but tiredness that lasts for weeks without an obvious reason is worth looking into. This article explains the usual causes, the conditions a GP may want to rule out and which self-help steps are sensible to try first.
When is tiredness normal, and when is it not?
According to the NHS, feeling tired from time to time is normal. A late night, a busy week, a bout of illness or a new baby in the house will all leave most people drained, and energy usually returns once the cause passes.
The picture changes when tiredness hangs around. The NHS advises seeing a GP if you have been tired for a few weeks and cannot explain why, if the tiredness is affecting your daily life, or if it comes with other symptoms such as weight loss or changes in mood. It is not an emergency in most cases, but it is a signal to find out what is going on rather than simply push through.
What are the everyday causes of tiredness?
Most persistent tiredness has an ordinary explanation. The NHS lists these among the common causes:
- Poor sleep or insomnia
- An unhealthy lifestyle, such as a poor diet and little exercise
- Stress, depression, or major life events such as bereavement or caring for a newborn
- Hormonal changes during puberty, pregnancy or the menopause
- Illnesses such as glandular fever and COVID-19
- Some medical treatments and medicines, such as chemotherapy, which can cause temporary drowsiness
Often several of these overlap. Poor sleep makes stress harder to manage, and stress makes sleep worse. If sleep is the likely culprit, the guides on why sleep matters for everyday health and insomnia and CBT for insomnia are good places to start. If work or caring pressures are behind it, understanding burnout covers what the evidence says.
Which medical conditions can cause tiredness?
Tiredness is a very non-specific symptom, which is why a GP will usually ask about everything else going on. The NHS highlights several conditions where it features, each with its own accompanying clues.
| Condition | Other signs the NHS mentions |
|---|---|
| Sleep apnoea | Loud snoring and gasping, snorting or choking noises at night |
| Iron deficiency anaemia | Low energy, heart palpitations, breathlessness, pale skin |
| Diabetes | Extra thirst, frequent urination (especially at night), weight loss |
| Overactive thyroid | Restlessness, nervousness, irritability, muscle weakness |
| Underactive thyroid | Feeling cold, weight gain, constipation, poor concentration, low mood, dry skin or hair |
| ME/CFS | Extreme fatigue that does not ease with rest, sleep problems, brain fog |
This table is a guide to patterns, not a way to diagnose yourself. Many of these symptoms have other causes, and plenty of people with tiredness have none of these conditions.
Could it be iron deficiency anaemia?
Iron deficiency anaemia is the most common type of anaemia, according to the NHS. It develops when the body has too little iron, often because of blood loss or pregnancy. Common symptoms are tiredness, low energy, shortness of breath, heart palpitations, paler skin and headaches.
The NHS lists several possible causes:
- Heavy periods
- Pregnancy, where it is usually due to low dietary iron
- Blood loss in the stomach or intestines, for example from anti-inflammatory medicines such as ibuprofen and aspirin, stomach ulcers, bowel or oesophageal inflammation or piles, and less commonly bowel or stomach cancer
That last point is why the cause matters as much as the anaemia itself. A GP will review your lifestyle and medical history and usually arrange a full blood count, which checks red blood cell levels and needs no preparation. If the cause is unclear, a faecal immunochemical test, which detects blood in stools, may be used and a referral to a specialist may follow.
Treatment depends on the cause. The NHS says iron tablets are usually taken for about six months, with repeat blood tests over several months to check levels. Side effects can include constipation, diarrhoea, stomach pain, heartburn, nausea and darker stools. Do not start iron tablets on a hunch: they should be taken on a GP’s advice, because the underlying reason for low iron needs finding, and they must be kept away from children.
Food can help alongside any treatment. The NHS suggests dark green leafy vegetables, fortified cereals and bread, meat, dried fruit and pulses, and notes that tea, coffee, milk and dairy foods, and foods high in phytic acid such as wholegrain cereals can reduce iron absorption.
What about the thyroid?
The thyroid gland in the neck produces hormones that influence energy and metabolism. According to the NHS, an underactive thyroid (hypothyroidism) is common, its symptoms are often mild and easy to miss, and they usually develop slowly. They include extreme tiredness, feeling cold, weight gain, constipation, poor concentration, low mood, dry skin or hair, hair loss, a hoarse voice and irregular or heavy periods.
The main UK cause is Hashimoto’s disease, an autoimmune condition. The NHS says it is most common in women and usually starts between 30 and 50, but anyone can be affected, and a family history of thyroid disease raises the risk. Diagnosis is by blood tests measuring thyroid-stimulating hormone and thyroxine. Treatment is usually a daily tablet of levothyroxine, typically lifelong, with regular blood tests to check the dose is right. With correct treatment, the NHS says people can generally live a normal life.
What is ME/CFS, and how is it different?
Myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS) is not simply “being very tired”. The NHS describes extreme tiredness that does not go away with rest, together with sleep problems, difficulties with thinking, concentration and memory, and post-exertional malaise, where symptoms worsen after physical or mental effort and can take a long time to settle.
There is no single test. Diagnosis rests on symptoms and on ruling out other conditions, and a GP may order blood and urine tests. The NHS says there is currently no cure, but energy management, cognitive behavioural therapy and medicines for symptoms such as pain and sleep problems can help people manage. Because symptoms overlap with other illnesses, it is worth seeing a GP for a proper diagnosis if you are not recovering from an illness as quickly as expected.
What can you try yourself first?
The NHS self-help advice is straightforward, and none of it is exotic. Its suggestions include:
- Eat a healthy diet and exercise regularly.
- Keep to regular sleep times and aim for 6 to 9 hours of sleep a night.
- Relax for a couple of hours before bed, for example by reading or listening to music.
- Keep the bedroom calm, dark, quiet and not too warm.
It also suggests avoiding smoking, drinking too much alcohol, eating, having caffeine or exercising in the two hours before sleep, and using phones or screens in the hour before bed. For ideas on cutting back, see our guide to alcohol units and practical ways to cut back.
A simple sleep and energy diary kept over two weeks, noting bedtimes, wake times, caffeine, alcohol and how you felt, can reveal patterns and gives a GP useful information. How strong is the evidence for these basics? Healthy sleep habits and regular activity are well supported as general health measures, but they will not fix tiredness driven by anaemia, thyroid disease or sleep apnoea, which is why persistent symptoms need checking rather than endless self-experimentation.
When should you speak to a GP or NHS 111?
Book a routine GP appointment if:
- You have been tired for a few weeks and cannot explain why.
- Tiredness is affecting your daily life.
- You have tiredness alongside other symptoms, such as weight loss or mood changes.
- Someone has told you that you gasp, snort or choke in your sleep.
Heavy periods, unexplained weight loss, breathlessness or palpitations alongside tiredness are good reasons to mention it sooner rather than later. If you feel suddenly very unwell, or are unsure how urgent your symptoms are, NHS 111 can advise you, and in an emergency call 999. For help choosing the right service in the capital, see choosing the right urgent care in London.
If low mood is part of the picture, NHS Talking Therapies can be accessed directly, as described in our guide to self-referral and what to expect.
Finding the cause rather than masking it
Tiredness is common and usually has an understandable cause, from poor sleep to stress. When it lingers for weeks, the sensible step is a conversation with a GP, who can arrange simple blood tests and look at the whole picture. Treating the cause, whether that is iron deficiency, an underactive thyroid or disrupted sleep, is far more effective than relying on caffeine to get through the day.
This is general information, not a substitute for advice from a doctor or other qualified health professional. If you are worried about your symptoms, speak to your GP or call NHS 111. If you are struggling emotionally, the Samaritans are available on 116 123.
Sources: NHS
