Delving deeper into their symptomatology may, however, prove to be rewarding. Nearly a third of patients who present feeling tired all of the time may have an identifiable pathological process.

Finding the cause
Considering the differential diagnoses will be helpful during the consultation.

In the first instance, it is important to clarify what the patient actually means by tiredness. Do they mean a lack of energy, fatigue, breathlessness, feeling low, day-time sleepiness, insomnia or weakness?

Asking the patient to tell you more about what they are experiencing by using open-ended questions is invaluable and exploring their ideas on why it happens may give you the underlying cause.

The characteristics of what the patient is experiencing should be discussed.

How long has it gone on for? Are they tired all the time or only sometimes? If sometimes, when? What is their lifestyle like? Do they sleep properly?

Are they happy or stressed/depressed? Is their weight stable? What medication/drugs do they take? Do they consume alcohol? Have they experienced night sweats?

Have they suffered any change in bowel habit or rectal bleeding? Are they breathless? If so, do they get breathless at rest or on exertion? Do they experience orthopnoea or palpitations? Do they have a cough or wheeze? Have they got symptoms of diabetes? A menstrual history is essential in women, while features of prostatism should be asked about in men.

Examination
Unless the cause of the tiredness is obvious, a general examination is imperative. Of course, a clear explanation as to why you need to examine a patient for tiredness is essential. Does the patient look depressed, jaundiced, breathless, cachectic, pale or hypothyroid? Do they have finger clubbing, signs of endocarditis, tremor, Dupuytren's contracture, palmar erythema or an abnormal pulse when examining the hands? Moving to head and neck, is there evidence of conjunctival pallor, lymphadenopathy or goitre?

Examination of the heart may reveal evidence of cardiac failure, arrhythmia or a murmur. Features of fibrosis, effusion or primary, metastatic or paraneoplastic disease may be found on respiratory examination.

When examining the abdomen, hepatomegaly may be suggestive of alcoholic or infective hepatitis, or malignancy.

Splenomegaly can be caused by connective tissue diseases, haematological disease such as leukaemia and myelofibrosis and infections. A mass may be palpated in the abdomen suggestive of bowel cancer.

Women may require a pelvic examination. Depression screening questionnaires may be appropriate and recent evidence has shown these to have a good negative predictive value.

Investigations
Most patients complaining of feeling tired all the time will have a normal clinical examination. If there is no obvious cause, it is reasonable to organise a series of general blood tests.

Ideally, tests should be tailored to the clinical picture. An FBC may reveal evidence of anaemia or infection. Renal failure and liver disease may present with fatigue. Thyroid function and blood glucose should also be checked. Hypercalcaemia may masquerade as depression and fatigue. An ESR may help rule out inflammatory diseases.

Screening
Women may require a pregnancy test and men a PSA test. Other tests include a glandular fever and coeliac screen.

Heart failure is not always easy to diagnose, but a normal ECG and chest X-ray virtually rules out left ventricular systolic dysfunction. An echocardiogram should otherwise be organised. An oxygen saturation reading may prove useful and sleep studies may be required.

The treatment of a patient who feels tired all of the time will include management of any underlying cause. If no cause can be found then general measures can be put in place. These include decent sleep hygiene, exercise, addressing life stresses, a good work-life balance and a healthy diet. Some patients may elect to have counselling.

Feeling tired all the time is a symptom rather than a disease. It is imperative to be clear what the patient means and to tease out any underlying cause. If a cause can not be found, general lifestyle measures should be encouraged.

• Dr Thakkar is a GP in Wooburn Green, Buckinghamshire

Learning points

• Let the patient tell you the story, the answer may become obvious.
• Nearly a third of patients have an underlying cause.
• Exclude important medical causes.
• Advise on lifestyle strategies.