Chronic fatigue syndrome can be misdiagnosed or overlooked because its symptoms are common to other disorders. Fatigue, for instance, is present during hundreds of illnesses. The nature of the symptoms can help distinguish CFS from other illnesses. And all symptoms of chronic fatigue are generally made a lot worse by physical or mental exertion of any kind.

The onset of chronic fatigue symptoms can be gradual or sudden, and often fluctuate in intensity. Sometimes symptoms are relatively mild; others are so severe that they require bed rest and need full-time care. It is common for the severity of the illness to wax and wane from day to day as well as over longer periods of weeks and months. Patients frequently experience periods of remission and relapse.

Symptoms of chronic fatigue
The main symptom of chronic fatigue is an overwhelming feeling of tiredness. This sensation varies from day to day, but is present more than half the time. The tiredness is so disabling, as to make it impossible to continue normal physical and mental activities.  Additionally, overwhelming fatigue is accompanied by other characteristic symptoms that last for at least six months and are used during diagnosis. These symptoms include:

• difficulties with memory and concentration
• headaches
• increased malaise (fatigue and sickness) following exertion
• joint pain (without redness or swelling)
• persistent muscle pain
• problems with sleep
• sore throat
• tender lymph nodes

Other symptoms
The symptoms listed above are the symptoms used to diagnose this illness. However, many CFS patients may experience other symptoms, including:

• allergies or sensitivities to foods, odors, chemicals, medications or noise
• brain fog
• chills and night sweats
• depression or psychological problems (irritability, mood swings, anxiety, panic attacks)
• difficulty maintaining upright position
• dizziness, balance problems or fainting
• irritable bowel
• visual disturbances (blurring, sensitivity to light, eye pain)

Types of chronic fatigue
Chronic fatigue syndrome is often categorized into four categories based on symptoms: mild, moderate, severe or very severe:

• Mild CFS - you are able to care for yourself, but may need to take days off work to rest. 
• Moderate CFS - you may have reduced mobility, and your symptoms can vary from time to time. You may also have disturbed sleep patterns and commonly sleep in the afternoon.
• Severe CFS - you are able to carry out minimal daily tasks, such as brushing your teeth, but occasionally you may need to use a wheelchair. You may also have difficulty concentrating.
• Very severe CFS - you are unable to carry out any daily tasks for yourself and rely on bed rest for the majority of your day. Often, in severe cases, you may experience intolerance to noise and become very sensitive to bright lights.

When to seek help
Even though fatigue is a common medical complaint, don't wait until you're so tired you can't get out of bed before seeing a doctor. If feelings of weariness or lethargy restrict you from particular activities, it's important to make an appointment. Perhaps you used to play tennis once a week without any problem, but now you get winded during the game. Or you might feel too tired to cook dinner or go out to a movie after work. These are good reasons to see a doctor.

Until recently, many people suffering from CFS symptoms were brushed off as psychiatric cases or were told "it's all in your head."  It's best to consult with a doctor who understands chronic fatigue syndrome, and can help you find a diagnosis.  Our next section on Chronic Fatigue Syndrome Diagnosis outlines what to expect during a doctor's office visit.  To learn how to diagnose chronic fatigue and learn the causes of extreme fatigue, continue reading here.