Lack of Energy. Your first step is to discover what's behind the lack of energy. Your primary care doctor can help by reviewing your history and medications, doing a physical exam, and checking some lab studies. Then you can work together to treat or relieve the problem. It could be as simple as allowing yourself more rest if you haven't been getting this. Psychiatric consultation may be helpful too.
Fix the cause. Lack of energy can come from a variety of situations. Dehydration (not drinking at least 5 cups of water a day), lack of sleep/poor sleep, skipping meals, stress, sleep apnea/snoring, chronic sinus problems, caffeine withdrawal, chronic illness (such as anemia) or allergies can cause low energy. See your doctor.