Dark urine could mean right now exposure to a chemical such as 2-butoxyethanol or any product with BUTYL. Have you done anything that causes you to have 'the sniffles?' a cold? or 'flu' symptoms? Farting? Diarrhea?
http://www.valdezlink.com/generic.htm#8
It is indicative of red blood cells dying of prematurely such as in autoimmune hemolytic anemia. I believe thisis the fatigue doctors are looking for in CFIDS
Avoid BUTYL or what ails you gets worse with more add on issues such as CFIDS, CFS, FM, ME
http://www.valdezlink.com/re/avoidpesticides.htm