Why Am I So Tired? The Many Causes of Fatigue

Medically Reviewed on 10/13/2020

What is fatigue?



What causes fatigue?




Fatigue as a symptom of underlying conditions


  • Are you possibly pregnant?
  • Have you started a new exercise or diet program?
  • Does any recent work change like extended hours or night shifts?
  • Any new stress (death of a family member, teenager rebellion, work pressures, divorce, financial problems)?
  • Are you taking any new medications?
  • Do you get tired at certain times (during or after your period, after interactions with a certain person, or after taking medicine)?
  • Any use of illegal or un-prescribed drugs, herbal products, or other supplements?


  1. sleep problems,
  2. mental health, and
  3. medications.

In addition, such questions can provide insight into short-term normal fatigue such as bereavement, exercise, or changes in normal activity.

Testing and further diagnosis for fatigue

The other types of questions are a bit harder for both the patient and the doctor to use as clues because if the patient responds positively, often the physician will need some additional testing is done (possibly by other doctors or tests with results that will not be immediately available to your physician) to uncover or clarify an answer. If you have a primary physician, that doctor should already have most of these questions partly or fully answered. However, the primary care doctor may not have these answers if you see multiple physicians, have not seen your doctor "...in quite a while..." or you are seeing a physician for the first appointment. Examples of such questions include:

Answers to these questions can lead to clues and further tests for underlying causes of fatigue that stem from:

These diseases listed between parentheses are only a few examples of the major categories of diseases and other fatigue problems that can stem from underlying diseases such as cancer, autoimmune diseases, and even therapy such as chemotherapy and radiation therapy.


Why do we sleep? See Answer

What is the prognosis for fatigue-causing disorders?

I find that most (unfortunately, not all) underlying causes of fatigue can be identified when the patient and I make a good effort to uncover the clues that lead to discovering the underlying cause of their fatigue. Treatment of fatigue is based on the treatment of the underlying cause, but that's another long story. Consequently, the answer to the person who asks "Why am I so tired?" is given when the underlying cause(s) is identified, usually done with you answering the tough questions accurately and the diligence in pursuing clues by your doctor.

Art and science are forever changing; in general diagnostic methods and how doctors use them often enhance patient care. However, many times our patients and we doctors don't think of the cumulative effects of lifestyle, minor changes in health, medication effects, and aging on one's overall health; we focus on a specific symptom and assume a single cause ant treatment. Functional medicine, a relatively new way to approach diagnosis and treatments may offer methods and treatments that are designed for each individual patient by identifying multiple causes that contribute to the problem and then trying multiple treatments to reduce or cure the problem. Chronic problems like fatigue, inflammation, and others may be solved or maximally reduced by the approach.

Health Solutions From Our Sponsors



The Institute for Functional Medicine. What is Functional Medicine?

UpToDate.com. Approach to the adult patient with fatigue.