HRT benefits and risks in plain numbers

SASian Anderson, Writer and editor, MyGLP. Sources checked 5 November 2026.

The short answer from the NHS and NICE

The NHS page on HRT benefits and risks says the benefits usually outweigh the risks, and the balance depends on your age, your symptoms and your own risk factors. NICE guideline NG23, last updated in November 2024, is the guideline GPs work to. NICE publishes a discussion aid with the figures below so you and your doctor can look at the same numbers.

The main types of HRT

• Oestrogen-only HRT is for women who have had a hysterectomy.
• Combined HRT adds a progestogen to protect the womb lining if you still have a womb.
• Oestrogen comes as tablets, or through the skin as patches, gel or spray.
• Vaginal oestrogen is a low dose used inside the vagina for dryness and urinary symptoms. The NHS says it does not raise breast cancer or clot risk.

Breast cancer per 1,000 women

The NICE discussion aid counts breast cancers diagnosed between the ages of 50 and 69 in women who start HRT at 50.

So for every 1,000 women on combined HRT for 5 years, about 921 will not get breast cancer between 50 and 69, compared with 941 who never take it. The NHS adds that the risk rises with longer use and falls after you stop.

For context, the British Menopause Society statement on HRT and breast cancer compares other risk factors in women aged 50 to 59 over 5 years. Obesity adds about 10 cases per 1,000 compared with a healthy weight, and drinking 35 to 44g of alcohol a day (about 4 to 5 units) adds about 8. The BMS notes the risk from HRT in past users is smaller than the risk from being overweight or drinking 2 or more units a day.

Blood clots: patches versus tablets

This is where the type of HRT changes the picture most. A 2019 BMJ study of UK GP records by Vinogradova and colleagues found oral HRT raised the odds of a clot in the leg or lung by 58%. HRT through the skin showed no rise in risk. The authors concluded transdermal treatment is the safest form for clot risk.

The BMS consensus statement on HRT puts the oral rise at two to four times and suggests HRT through the skin first for women with clot risk factors, such as a raised BMI. Micronised progesterone and dydrogesterone also carry a lower clot risk than other progestogens.

Stroke, heart disease, womb cancer and bones

Sequential HRT gives a monthly bleed and continuous combined HRT does not. The NHS says you need a progestogen as well as oestrogen if you still have a womb. NICE shows why: oestrogen alone in a woman with a womb adds 7 womb cancers per 1,000.

The fracture figure is the largest number in the whole aid. HRT prevents bone loss, and the NHS says this matters most if your periods stopped before 45. Our early menopause guide covers this in detail.

What the 2002 WHI study got wrong

In 2002 the US Women's Health Initiative stopped its combined HRT trial early. The JAMA paper reported more breast cancer, heart disease, strokes and clots in the HRT group,. Many women stopped HRT, and many more never started.

The details mattered. The trial enrolled 16,608 women aged 50 to 79 with an average age of 63, many years past their menopause. A CMAJ summary sets out the absolute figures per 10,000 women each year: 8 more breast cancers, 7 more heart events, 8 more strokes and 18 more clots, against 5 fewer hip fractures and 6 fewer bowel cancers. Per 1,000 women a year, the extra breast cancer figure is under 1.

Follow-up changed the picture. An 18-year analysis of 27,347 WHI women, published in JAMA in 2017, found HRT was not linked to any rise in death from all causes, heart disease or cancer. The BMS now says that for women under 60 or within 10 years of the menopause, HRT is linked to lower heart disease and lower death rates overall.

Body-identical, bioidentical and the difference

Body-identical HRT means licensed estradiol (usually through the skin) with micronised progesterone. These are regulated medicines, available on the NHS. The BMS says observational data suggest micronised progesterone and dydrogesterone carry a lower breast cancer risk than other progestogens.

Compounded "bioidentical" hormones from private clinics are different. The BMS points out these products have not been through the same regulatory checks or randomised trials as licensed HRT, and the same benefits are available from licensed products.

Who may be told HRT is not suitable

NICE says hormonal treatment is not suitable for everyone, for example women with a history of breast cancer or another oestrogen-sensitive cancer. Past clots or a high clot risk usually mean HRT through the skin rather than no HRT. The BMS says there should be no arbitrary limit on how long you take HRT. Dose and length are worked out with you based on symptoms and response.

For hot flush treatments with and without hormones, read the hot flushes guide. For checking your breasts and what to report, see breast checks and symptoms. The menopause weight gain guide explains why patches suit women with a raised BMI.

Sources

1. Benefits and risks of HRT (NHS)
2. Menopause: identification and management (NG23) (NICE)
3. Incidence of medical conditions with and without HRT: a discussion aid (NICE)
4. Use of hormone replacement therapy and risk of venous thromboembolism (Vinogradova et al, BMJ, 2019)
5. BMS and WHC recommendations on HRT in menopausal women (British Menopause Society and Women's Health Concern)
6. Benefits and risks of HRT before and after a breast cancer diagnosis (British Menopause Society)
7. Risks and benefits of estrogen plus progestin in healthy postmenopausal women (WHI) (Writing Group for the WHI Investigators, JAMA, 2002)
8. Summary of the WHI estrogen plus progestin trial (Canadian Medical Association Journal, 2002)
9. Menopausal hormone therapy and long-term all-cause and cause-specific mortality (Manson et al, JAMA, 2017)
10. Premature menopause (information for the public) (NICE)