Although there is a lot of evidence that chronic fatigue syndrome is caused by a physical problem involving the immune system, energy metabolism and the nervous system, there is no laboratory test or procedure to confirm the diagnosis. Until a better way is found, doctors must diagnose chronic fatigue syndrome based on whether a person has the symptoms of the illness and by eliminating other illnesses that can cause long-lasting fatigue.
For this reason, your doctor will ask about symptoms of other fatigue-causing illnesses including:
Hypothyroidism (underactive thyroid gland)
Adrenal insufficiency (underactive adrenal gland)
Sleep apnea or narcolepsy
Side effects of medications
Hepatitis B or hepatitis C
Certain psychiatric illnesses, especially major depression, bipolar disorder, schizophrenia and delusional disorders and dementia
The eating disorders anorexia nervosa and bulimia
Drug abuse, including alcohol abuse
Your doctor will examine you and assess your mental status. Some basic blood tests may be ordered, such as a red blood cell count (hematocrit), white blood cell count and differential white blood cell count, thyroid, kidney and liver tests. Additional, more specialized testing may be needed, including testing of your autonomic nervous system.