As with any treatment, HT is not risk free. Estrogen therapy causes the lining of the uterus to grow and can increase the risk of uterine cancer. However, adding progestin lowers the risk of uterine cancer to less than that in women who do not take HT.

In women who take HT, spotty bleeding may occur. Some women even get heavier bleeding like that of a menstrual period.

There is an increased risk of breast cancer in women who use combined hormone therapy. The increase appears to be small, but increases depending on how long a women takes hormone therapy. Hormone therapy also modestly increases the risk of heart attack, stroke and blood clots.