Fatigue and sleepiness can be difficult to diagnose, and also hard to define. A definite diagnosis is made when you have severe and chronic fatigue and sleepiness that lasts for six months or more, and other medical conditions that could cause it must be excluded. The disorder must significantly interfere with work or daily activities and present other symptoms listed above such as sore throat, headache, unexplained muscular pain etc.
There's no single test to confirm this diagnosis. Since the symptoms are related to many other health problems, it becomes difficult to diagnose. Your doctor will attempt to rule out a number of other illnesses before giving a definite diagnosis. These include:
Sleep disorders: chronic fatigue and sleepiness can be caused by sleep disorders. A sleep study can determine if your rest is being disturbed by disorders such as obstructive <sleep apnea>, <restless legs syndrome> or <insomnia>.
Medical problems: fatigue and sleepiness is a common symptom in several medical conditions, such as anaemia, <diabetes> and underactive thyroid (<hypothyroidism>). Lab tests may be conducted to examine your blood for evidence of some of the top suspects.
Mental health issues: fatigue and sleepiness is also a symptom of a variety of mental health problems, such as <depression>, <anxiety>, <bipolar disorder> and <schizophrenia>. A counsellor can help determine if one of these problems is causing your fatigue.