Many premenopausal women run a borderline iron deficiency without realizing it--we lose iron monthly because of menstruation, and it's a difficult mineral for our bodies to absorb. Low iron can definitely make you feel tired. Best dietary sources: meat, beans, fish, poultry, tofu, spinach, pumpkin seeds, tomato sauce, clams, oatmeal & whole grains. Also, try cooking with a cast-iron pan--it increases dietary iron. And have a big glass of OJ with that steak or spinach salad: vitamin C improves iron absorption. (For more energy boosters, read this [1].)