Testosterone levels are highest in the morning. Blood for testosterone lab tests should be drawn between 7 a.m. and 10 a.m. Based on this blood test, your doctor must determine if your total testosterone level is low.Unfortunately, different laboratories measure total testosterone using different methods.estosterone can’t have any effect on your body unless it is floating freely in the blood. A man can have normal or even high levels of total testosterone, but low levels of free testosterone.