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An overview of Fatigue and it's wide range of potential causes

Posted by Eamonn Brady on

Fatigue: Causes


Fatigue negatively impacts work performance, family life, and relationships.


 Possible causes of fatigue:

  • Lifestyle related
    • Malnutrition
    • Unhealthy diet
    • Smoking
    • Alcohol consumption
    • Drug abuse
    • Stress
  • Physical conditions such as:
    • Anaemia- Low haemoglobin (red blood cells) often caused by low iron or the like of heavy periods in women
    • Diabetes
    • High blood pressure
    • Obesity
    • Heart disease
    • Chronic fatigue syndrome


  • Mental health conditions including depression, anxiety disorders and PTSD
  • Classes of meds that cause fatigue:
    • High blood pressure medicines such as beta blockers
    • Statins and fibrates (for cholesterol)
    • Proton pump inhibitors (to reduce stomach acid)
    • Benzodiazepines (used for anxiety type disorders)
    • Antihistamines: non drowsy antihistamine can even cause drowsiness in 15% of people
    • Antidepressants
    • Antipsychotics
    • Antibiotics


Treatment of fatigue should include regular physical activity consisting of stretching and aerobic exercise, such as walking. Caffeine may be useful for temporary alertness. Short naps are proven performance enhancers. Antidepressants called selective serotonin reuptake inhibitors like fluoxetine and sertraline can improve energy levels in people with depression. People with chronic fatigue can be helped with cognitive behaviour therapy (CBT).


Men versus women

In general terms, research shows men and women describe fatigue differently:

  • Women tend to describe fulling depressed or anxious.
  • Men tend to describe being tired


No cause can be found approximately 33% of cases of fatigue.


Sleepiness versus Fatigue

Sleepiness is caused by inhibition of our normal arousal mechanism. When feeling sleepy, activity can ease the feeling of sleepiness, whereas fatigue can be worsened by activity especially short term (as longer term, activity and exercise helps ease fatigue. People experiencing sleepiness will feel more awake after a short sleep (nap), but if experiencing fatigue, people describe lack of energy, mental fatigue, a lack muscle endurance and delayed recuperation after physical activity and they find sleep does not ease these symptoms/ feelings.


Secondary fatigue

Secondary fatigue is caused by an underlying medical condition and may last one month or longer, but it lasts less than six months.


Secondary causes of fatigue include lymphadenopathy (tumour spread or recurrence), cardiac murmurs (endocarditis), goitre (thyroid hormone imbalance), oedema (heart failure, liver disease, or malnutrition), poor muscle tone (advancing neurological condition such as Huntington’s disease or motor neurone disease), and neurologic abnormalities (stroke or brain metastases/ cancer).


Taking bloods to check for the likes of anaemia or low thyroid only finds the cause of fatigue in about 5% percent of people. Women of childbearing age should receive a pregnancy test to rule out pregnancy as a cause of fatigue. Those with cancer, kidney disease, or other chronic conditions associated with anaemia are less likely experience fatigue if their haemoglobin level is at 10 g per dL (100 g per L) or above. Non-anaemic, menstruating women who have low normal ferritin levels report increased energy after four weeks of iron supplementation.


Physiologic fatigue

This is a feeling of fatigue caused by things such as lack of exercise, boredom, or mental stress that results in lack of energy and depression. It is often relieved with rest.


Chronic fatigue

Chronic fatigue is diagnosed in those experiencing fatigue for more than six months. Medical conditions may cause or contribute to chronic fatigue


Causes of Chronic Fatigue

  • Heart or lung related: Congestive heart failure, COPD, peripheral vascular disease, and angina
  • Sleep disturbance: Gastro-oesophageal reflux disease, sleep apnoea, allergic or vasomotor rhinitis
  • Endocrine: Diabetes, low thyroid levels, high calcium levels, chronic kidney disease, liver failure, adrenal insufficiency, or pituitary insufficiency
  • Infection: Tuberculosis, hepatitis, HIV, endocarditis, mononucleosis, parasitic disease
  • Inflammation: rheumatoid arthritis, systemic lupus erythematosus
  • Medication: sedative-hypnotics, analgesics, high blood pressure medicines, antidepressants, muscle relaxants, opioid analgesics such as codeine, antibiotics, or substance abuse
  • Psychological: depression, anxiety


For comprehensive and free health advice and information call in to Whelehans, log on to or dial 04493 34591 (Pearse St) or 04493 10266 (Clonmore). Email queries to Find us on Facebook


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