Persistent Fatigue: Common Causes, Red Flags and Assessment

What do you mean by tired?

Start with what has changed. Do you want to fall asleep during the day? Do your muscles feel weak? Or does a small task leave you with no energy? These can feel similar, but the details help a doctor decide what to check. Tell them what you could do before and what is now hard.

A poor night’s sleep can explain a tired day. Ongoing fatigue is different if rest does not help, the pattern is new, or work and home life are becoming difficult. You do not need to find the cause yourself before asking for help. Fatigue is a symptom, not a diagnosis. [1]

When should you seek help?

The symptoms that occur with tiredness matter more than a score on an energy scale. Use the guide below to choose a next step. It cannot cover every situation: if you are rapidly getting worse or feel seriously unwell, seek urgent advice.

Common causes worth considering

There may be more than one contributor. Sleep loss, stress, low mood, recent illness, medicines and some medical conditions can cause fatigue. A sensible review starts with your history. It does not begin by assuming that everyone has a hormone imbalance, a nutrient deficiency or a hidden gut problem.

Sleep and daily demands

Think about both the hours you sleep and how rested you feel. Shift work, caring duties and a changing sleep schedule can make sleep difficult. Loud snoring, choking or gasping at night, and strong daytime sleepiness deserve medical attention. A sleep disorder needs its own assessment; simply spending longer in bed may not solve it. [4]

Physical health and medicines

Anaemia, thyroid disease and diabetes are among the conditions a clinician may consider, depending on other symptoms and the examination. Bring a list of all medicines, supplements and recent dose changes. Ask whether any could contribute, but do not stop a prescribed medicine on your own. A list of possible causes is not a list of tests that every person needs. [1]

Mood, stress and recovery after illness

Stress and low mood can affect sleep, energy and the effort needed for daily tasks. These are real health concerns. They can also occur alongside a physical illness. Tell the clinician about both, rather than feeling you must choose one explanation. If symptoms began after an infection, record when it happened and how your ability to manage activity has changed.

Keep a simple one-week history

A short record can make an appointment easier. It is a way to show the pattern, not a test you must pass to be taken seriously. Do not delay seeking help to complete it. A few notes each day are enough; there is no need to buy a tracker.

• Note when the fatigue started and whether it is steady or comes in spells.
• Record bedtimes, wake times, naps and how rested you feel.
• Write down one or two tasks that are now harder, such as shopping or climbing stairs.
• Include other symptoms, recent illness, changes in weight and, where relevant, heavy periods.
• List medicines and supplements, with any recent change.
• Note what happens after activity, including a worsening that appears later that day or the next.
• Bring earlier results and explain what has already been tried.

You can use plain examples: “I now need to rest after a shower” tells a doctor more about the impact than “my energy is low”. If you can only manage a short appointment, choose your main concern and the change that worries you most. A friend or relative may help you recall details if you want them involved.

What happens at a medical review?

The clinician asks about the timeline, sleep, mood, diet, medicines and other symptoms. They may examine you and discuss blood tests or other checks. The choice depends on the findings. Ask what each test is meant to answer, what a result could change and when you should hear back.

Normal initial results can be useful without explaining every symptom. Agree what happens next if fatigue continues: when to return, which changes need earlier review and who will look at the whole picture. Keep a copy of the plan. This is more useful than repeating a broad panel without a clear question.

Our fatigue assessment page explains the practice’s approach. You can also read about assessment of persistent symptoms and how testing decisions are made. Private testing is not a required first step for everyone.

What can you do while waiting?

Try to keep regular meals and sleep times that fit your circumstances. Share essential tasks if you can. Avoid treating a long list of assumed deficiencies with supplements. If activity causes a marked or delayed worsening, tell the clinician and avoid pushing through it to meet a fixed exercise target.

Persistent fatigue alone does not establish ME/CFS. Where that condition is suspected, activity advice needs care. NICE advises against fixed increases in exercise for people with ME/CFS. A personalised plan should take account of symptoms and the person’s current limits. [5]

The aim before review is to gather useful information and manage the day as safely as you can. You do not need to solve the problem with a new diet, a device or a supplement first.