For the woman using hormone therapy, a sufficient level of estrogen in the bloodstream is important to assure protective effects on her heart and bones. Studies show an estradiol (estrogen) level of over 40 pg/ml to be protective against bone loss. Most experts recommend a level of 60 pg/ml or greater to provide the best relief of menopause symptoms such as hot flashes. Levels over 150-250 pg/ml are usually higher than needed. It is important to plan any reduction in levels as a gradual tapering process, in order to minimize the risks of estrogen withdrawal symptoms, such as hot flashes. Different brands of estrogen contain different types of estrogens, which may effect the exact blood of estradiol, the most active type of estrogen.