In low risk women and if started within 10 years of the menopause or below the age of 60, the benefits of HRT usually outweigh the small risks. HRT is generally not a suitable treatment for women with breast cancer or women who have had breast cancer in the past.
The risks of HRT depend on the type and dose of HRT you are given and other individual factors such as your age, general health and lifestyle.
Oral HRT increases the risk of blood clots, strokes and gallbladder problems. However, transdermal HRT does not come with these increased risks.
Synthetic progestogens (not body identical) used in combined HRT have been shown to cause a small increased risk of breast cancer in women over and above women not using HRT. If you followed a group of 1000 women aged between 50-59 years old for 5 years, there would be an additional 4 cases of breast cancer in this group. This is a very small increased risk and it is worth noting that obesity causes an additional 24 cases of breast cancer and drinking more than 2 units of alcohol per day leads to an additional 5 cases of breast cancer.
There is no evidence of a significantly increased risk of breast cancer if you have had a hysterectomy in the past, and are only taking oestrogen without a progestogen.