Fatigue is a symptom and not a condition, which is caused by an underlying medical condition. Despite all the conducive factors for good health, such as proper sleep and nutrition, regular exercise and being accomplished, if you experience fatigue, medical attention is required.

Fatigue symptoms could be emotional, physical or mental:
- Continued tiredness and sleepiness
- Headache and dizziness
- Loss of appetite
- Weak, aching or sore muscles
- Delayed reflexes and responses
- Impaired coordination or decision- and judgement-making problems
- Mood swings or hallucinations
- Reduced immunity or visual changes
- Issues with memory and concentration

The causes of fatigue are:
- Medical: Underlying diseases, such as diabetes or thyroid or heart disorder
- Lifestyle-related: Lack or excess or disturbed sleep, drug or alcohol overuse, physical inactivity or improper diet
- Workplace-related: Shift work, stress or improper practices, workaholic nature or unemployment
- Emotional: Grief, depression, stress and anxiety stress

In clinical depression, the brain is deprived of a chemical called serotonin required for the functioning of the internal body clock. Decreased levels of serotonin tend to lower your energy levels, thereby making you feel tired or weak. Hence, if you are suffering from depression, you will experience chronic fatigue.

You should consult a doctor for fatigue if you experience the following symptoms:

- Suicidal thoughts
- Thoughts of self-harming or others
- Breathing difficulty
- Irregular heartbeat
- Feeling drained
- Severe pain in the head, back, chest, abdomen or pelvis
- Blood in vomitus or rectal bleed
- Fatigue lasting for two or more weeks even after adequate rest