I am almost 25 years old, in a healthy wieght range for my height. I am always tired. I recently started training for a half marathon, (i ve run on and off for 10 years) and I cannot do it. My body is not allowing me run, one mile exhausts me. I thought that surely after a month or two my stamona would improve and kick in, but it has not, if anything I feel it decreasing and my energy everyday getting worse instead of stronger. I get 7-8 hours of sleep most nights. I am just can t explain why I have no energy. I ve tried changing my diet, but that hasn t helped either. Also I have to go go to the bathroom 4-5 times a day, I don t know if that s impacting anything or not, just really annoying. I have t gone more than 2 weeks with out running once or twice a week in the last year, so I just don t understand this excessive tiredness and lack of energy.