When deciding whether to have hormone replacement therapy (HRT), it's important to understand the risks.

It's also important to consider HRT as only one of a range of interventions to improve your menopausal and post-menopausal health and wellbeing.

Many studies on HRT have been published over the past 15 years that have highlighted the potential risks. As a result, some women and doctors have been reluctant to use HRT.

But more recent evidence and the National Institute for Health and Care Excellence's (NICE) new guidelines say that the risks of HRT are small and are usually outweighed by the benefits.

This page covers HRT and the risks of:

Breast cancer

Ovarian cancer

Womb cancer

Blood clots

Heart disease and strokes

Breast cancer

NICE says:

  • taking combined HRT (oestrogen and progestogen) is associated with a small increased risk of breast cancer – some studies have suggested that for every 1,000 women taking combined HRT, there will be around five extra cases of breast cancer (from a normal risk of 22 cases of breast cancer per 1,000 menopausal women to 27)
  • the risk of breast cancer decreases when you stop taking HRT – estimates suggest the level of risk returns to normal after about five years
  • oestrogen-only HRT is associated with little or no change in the risk of breast cancer

Because of the risk of breast cancer, it's especially important to attend all your breast cancer screening appointments if you're taking combined HRT.

Ovarian cancer

Studies looking at whether HRT can increase your risk of ovarian cancer have so far had conflicting results.

It's thought that if there is any increase in cases of ovarian cancer in women taking HRT, the risk is very small.

A recent study found that for every 1,000 women taking HRT for five years, there will be one extra case of ovarian cancer.

Any risk of ovarian cancer is thought to decrease once you stop taking HRT.

Womb cancer

Oestrogen-only HRT can increase the risk of womb cancer (also called endometrial cancer), which is why it's only used in women who don't have a womb (for example, because they've had a hysterectomy).

Taking combined HRT, particularly a course of continuous HRT (where you take both medications without a regular break), largely eliminates this risk.

If you still have a womb and you're taking HRT, it's important to take both medications as advised by your doctor to avoid increasing your risk of womb cancer.

Blood clots

Blood clots can be serious if they become lodged in a blood vessel and block the flow of blood.

NICE says:

  • taking HRT tablets can increase your risk of blood clots
  • there's no increased risk of blood clots from HRT patches or gels

It's thought the risk of developing a blood clot is about two to four times higher than normal for women taking HRT tablets. But as the risk of menopausal women developing blood clots is normally very low, the overall risk from HRT tablets is still small.

It's estimated that for every 1,000 women taking HRT tablets for 7.5 years, less than two will develop a blood clot.

Heart disease and strokes

NICE says:

  • HRT doesn't significantly increase the risk of cardiovascular disease (including heart disease and strokes) when started before 60 years of age
  • oestrogen-only HRT is associated with no, or reduced, risk of heart disease
  • combined HRT is associated with little or no increase in the risk of heart disease
  • taking oestrogen tablets is associated with a small increase in the risk of stroke, although the normal risk of women under 60 having a stroke is very low, so the overall risk is small

Speak to your GP if you're taking HRT or are considering taking it and are worried about the risk of stroke or heart disease.

Page last reviewed: 20/07/2016

Next review due: 20/07/2019