Fatigue can be defined as the tiredness that just does not go away and does not have an obvious explanation (such as working out too much the day before, staying up late last night, etc). It is often associated with generalized weakness and what is often described as "a brain fog". The presence of true fatigue warrants a visit to your physician for a medical evaluation to make sure it does not have a pathological cause. The five conditions discussed below are some of the most common explanations of fatigue that physicians diagnose their patients with.
1. Anemia - a condition that occurs when red blood cell concentration drops down below what is considered normal. This can be detected with quick and inexpensive blood tests that measure blood values known as hemoglobin and hematocrit (often part of a more comprehensive test called Complete Blood Count or CBC for short). There may be many different explanations to it, some are common (such as having heavy periods for a female), and some are due to rare medical conditions. In each case, raising your blood count back to normal will result in significant improvement of fatigue.