Consider drugs or toxins ([alcohol], illicit drugs, sedating medications such as [antihistamines], [beta blockers], or [nonsteroidals], including over-the-counter and herbal medications, and occupational toxin exposures). Neurologic disease (e.g., #multiple sclerosis#, #Parkinson disease#, #postpolio#, #seizures#), and medical disease can cause fatigue. #Adrenal insufficiency# may present as fatigue but usually is associated with [orthostatic hypotension]. #Hypothyroidism#, #hypopituitarism#, #asthma#, #sarcoidosis#, [anemia], #lupus#, #hepatitis#, #chronic infections#, and #malignancy# have all been identified in case series. Many illnesses produce [severe fatigue], but usually other symptoms are more prominent (e.g., #heart failure#, #tuberculosis#).