Diagnosis

There's no single test to confirm a diagnosis of chronic fatigue syndrome. Symptoms can mimic those of many other health problems, including:

• Sleep disorders. Chronic fatigue 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 is a common symptom in several medical conditions, such as anemia, diabetes and underactive thyroid (hypothyroidism). Lab tests can check your blood for evidence of some of the top suspects.
• Mental health issues. Fatigue is also a symptom of a variety of mental health problems, such as depression and anxiety. A counselor can help determine if one of these problems is causing your fatigue.

It's also common for people who have chronic fatigue syndrome to also have other health problems at the same time, such as sleep disorders, irritable bowel syndrome, fibromyalgia, depression or anxiety.

In fact, there are so many overlapping symptoms between chronic fatigue syndrome and fibromyalgia that some researchers consider the two disorders to be different aspects of the same disease.

Diagnostic criteria

Guidelines proposed by the United States Institute of Medicine define the fatigue associated with chronic fatigue syndrome as being:

• So severe that it interferes with the ability to engage in pre-illness activities
• Of new or definite onset (not lifelong)
• Not substantially alleviated by rest
• Worsened by physical, mental or emotional exertion

To meet the Institute of Medicine's diagnostic criteria for chronic fatigue syndrome, a person would also need to experience at least one of these two symptoms:

• Difficulties with memory, focus and concentration
• Dizziness that worsens with moving from lying down or sitting to standing

These symptoms must last for at least six months and occur at least half the time at moderate, substantial or severe intensity.