Testosterone is a mystery to most people other than what medical professionals and medical laboratories write or say about the subject. The fact is that testosterone, as it is known to most folks, assists in growing muscle mass and sex drive. Another fact that is not known really at all is that it is great for the body’s blood. The hormone testosterone is a very important factor in the body’s process of building red blood cells, known scientifically as erythropoiesis. Feel tired, have low testosterone according your blood tests and what your doctor tells you, then it most likely stems from low testosterone levels. The lower the body’s red blood cell production the lower energy a person tends to have throughout the day.