Why Am I So Tired? The Many Causes of Fatigue

Medical Author:
Medical Editor:

What is fatigue?

One of the most common complaints that I hear when taking a history from a patient of a current illness is that the patient says, almost as an afterthought "... and I don't know why I am so tired." In most instances, this complaint is not the main reason that the patient is seeing me. In some instances, "being tired" is mentioned to physicians during a routine checkup after the patient said they have no current health concerns. So, should I as a physician treat the comment like an afterthought and concentrate on the "real reason" the patient is being seen? I could focus on the "real reason" for the visit, but if I skip asking questions about "being tired," I may miss finding out information or clues about the patient's illness and completely overlook a potential diagnosis and treatment for the patient.

Therefore, the first thing to understand about "tired" is what the patient means by the word. Does the patient mean they feel sleepy or fatigued -- they are not the same. Fatigued (tired) describes a lack of energy and motivation, not feeling sleepy (although both can occur together). If the answer is fatigue, the next step is to determine if the fatigue is mental, physical, or both. Now we are beginning to narrow down some clues to the cause of the fatigue, but we (the patient and the doctor) still have a long way to go together.

What causes fatigue?

Fatigue is mainly a symptom and not a disease in itself. The key is for the doctor, with the patient's help, to discover the underlying cause of fatigue. The patient's input is important because accurate answers to the doctor's questions may lead the doctor toward a diagnosis or, at least, may suggest what medical tests may help provide a diagnosis. For example:

  • If the patient says things like "Starting any project is tiring...It is exhausting to get motivated... Concentration takes all of my energy....or... it takes so much effort just to feel normal," the fatigue may have a mental cause.
  • If the patient says things like "I'm exhausted after walking up a flight of stairs...I lose muscle strength after simple repetitive movements..., or I had a viral infection but now I seem unable to get my normal strength back," the fatigue may have a physical cause.

However, there are reasons that are "normal" for a person to be tired. Normal people who have intense physical or mental challenges can become fatigued. If the intense activity is halted (for example, "Whew! The exam is over"... or... "I had to really run to catch Fluffy after her leash broke"), the fatigue gradually dissipates over hours or a day. When patients describe longer-lasting fatigue or fatigue with otherwise normal activity, then it may be telling the patient and their doctor there is an underlying cause of their tiredness.

Why Am I So Tired? The Many Causes of Fatigue Resources

Read patient comments on Fatigue - Causes

Doctor written main article on Fatigue

Medically Reviewed by a Doctor on 1/11/2017

Health Solutions From Our Sponsors