Feeling tired from time to time is a normal part of life. But when you ask yourself “why am I always tired?” week after week, it deserves attention. Persistent tiredness is one of the most common reasons people book a doctor’s appointment, and in most cases it has an everyday explanation that can be improved.
This guide explains the usual causes of ongoing tiredness, the self-help steps that often make a difference and the signs that mean you should get medical advice. It is based on public guidance from the UK’s National Health Service and is general education, not a diagnosis. Please read our medical disclaimer before acting on anything here.
In this guide
Everyday causes of tiredness
Most long-lasting tiredness comes from lifestyle and daily circumstances rather than a serious illness. Common contributors include:
- Poor or too little sleep. Irregular bedtimes, screens late at night, noise, an uncomfortable bed or a busy mind can all reduce sleep quality.
- Stress and worry. Ongoing pressure at work, at home or about money is exhausting, both mentally and physically.
- Too little or too much exercise. Being very inactive can leave you drained, and so can overtraining without enough rest.
- Diet and drinks. Skipping meals, relying on sugary snacks, drinking lots of caffeine or alcohol, and not drinking enough water can all affect energy.
- Weight changes. Being overweight or underweight can contribute to tiredness.
- Shift work and jet lag. Disrupting your body clock makes it harder to rest properly.
- Caring and parenting. Broken nights and constant demands are an obvious but often overlooked cause.
Medical causes worth knowing about
Sometimes tiredness is a symptom of a health condition. Public health guidance lists several possibilities, including:
- Anaemia. A low level of red blood cells or haemoglobin can leave you weak and short of breath. A complete blood count is the usual way to check.
- Underactive thyroid. When the thyroid gland produces too little hormone, tiredness, weight gain and feeling cold are common.
- Sleep problems. Conditions such as obstructive sleep apnoea or insomnia disturb sleep even when you think you slept enough.
- Diabetes. Tiredness can come with increased thirst, frequent urination and weight loss.
- Depression and anxiety. Low mood, loss of interest and worry often show up as fatigue.
- Infections and recovery. Tiredness can linger after an illness, and some infections cause long-lasting fatigue.
- Medicines. Some prescription medicines list drowsiness as a side effect.
- Other conditions. Heart, kidney or liver problems, and some long-term conditions, can also cause fatigue.
This list is not a checklist to diagnose yourself. Many of these conditions share similar symptoms, and only a clinician can work out which, if any, applies to you.
Self-help steps that can boost energy
If there are no worrying symptoms, a few changes over several weeks often help:
- Keep a regular sleep routine. Go to bed and wake up at similar times, keep the bedroom cool, dark and quiet, and wind down without screens for an hour beforehand.
- Move your body. Regular activity, such as a brisk daily walk, can improve energy and sleep. Build up gradually.
- Eat regularly and balance your meals. Include fruit, vegetables, whole grains and protein, and stay hydrated.
- Cut back on caffeine and alcohol, especially in the afternoon and evening.
- Reduce stress. Try relaxation techniques, set realistic limits on commitments and make time for things you enjoy. Talking to someone you trust can help.
- Keep a simple tiredness diary. Note when you feel worst, what you ate, how you slept and what was happening that day. Patterns often appear.
When to see a doctor
Book an appointment if your tiredness:
- has lasted for several weeks without improving, despite rest and the steps above;
- is severe, is getting worse or stops you from doing your normal activities;
- comes with unexplained weight loss, a persistent fever, night sweats or swollen glands;
- appears alongside breathlessness, a fast or irregular heartbeat, dizziness or looking very pale;
- occurs with persistent low mood, loss of interest or anxiety;
- involves loud snoring with pauses in breathing, or falling asleep during the day without meaning to.
Seek urgent medical help if tiredness comes with chest pain, severe shortness of breath, fainting, confusion or thoughts of harming yourself. In an emergency, contact your local emergency number.
Getting the most from your appointment
The clinician will usually ask about your sleep, mood, diet, medicines and daily life, and may examine you or arrange blood tests. Bringing your tiredness diary and a list of everything you take will help. Our step-by-step guide on how to prepare for a doctor’s appointment covers what to write down and which questions to ask.
Good questions for this visit include: “What could be causing my tiredness?”, “Which tests do you recommend and why?”, “Could any of my medicines be involved?” and “When should I come back if nothing changes?”
Frequently asked questions
Is it normal to feel tired all the time?
Occasional tiredness is normal, and many people feel worn out during busy or stressful periods. Tiredness that lasts for weeks, is not relieved by rest, or affects daily life is not something you have to put up with, and it is worth discussing with a doctor.
Can anaemia cause constant tiredness?
Yes. Anaemia reduces the oxygen your blood can carry, which commonly causes tiredness, weakness and breathlessness. A blood test can show whether it applies to you.
Can stress and anxiety make me exhausted?
Yes. Ongoing stress keeps the body on alert and often disrupts sleep, so mental strain can leave you physically drained. If low mood or worry is a regular feature, tell your doctor.
Will a blood test find the cause?
Sometimes. Blood tests can check for problems such as anaemia, thyroid issues or diabetes, but many people with tiredness have normal results, and the cause is then found through lifestyle, sleep or mood.
How long should I wait before seeing a doctor?
Public health guidance suggests seeing a doctor if tiredness has lasted a few weeks despite sensible self-help, or sooner if you have other concerning symptoms such as unexplained weight loss or breathlessness.
Key takeaways
Constant tiredness usually has a common, treatable cause such as sleep habits, stress or diet, but it can also be a sign of an underlying condition. Try the self-help steps, track your symptoms and do not delay seeing a doctor if it persists or comes with other symptoms. To learn how we research our guides, see our editorial policy, or browse more symptom and condition guides.
Source: NHS, Tiredness and fatigue.
