Few subjects in women's health are as charged, or as muddled, as HRT. So let's separate what the evidence says from what fear and headlines have made of it.
One important note before we start: this is education, not medical advice. HRT is an individual decision to make with a clinician who knows your history.
Around 2002, early findings from a large study, the Women's Health Initiative, were reported in a way that made HRT sound dangerous, and prescriptions fell off a cliff worldwide. In the years since, researchers have re-analysed that data and run further studies, and the conclusions have shifted considerably.
Three details explain most of the shift, and none of them made the headlines.
The women were older than you think. The average participant was 63, and most were well past menopause. Only a minority were in their fifties with symptoms, which is precisely the group that actually takes HRT. A trial of hormones in women a decade past the transition was reported as though it described a woman of 51 with night sweats.
It tested one specific combination. Conjugated equine oestrogen with medroxyprogesterone acetate, taken orally. That is not what most women are prescribed today.
The numbers were reported as percentages. "A 26% increase" is a relative risk, and relative risks are how you frighten people with small numbers. The absolute figures were always available and almost never printed.
Here is what the UK regulator publishes, per 1,000 women aged 50 to 69, using HRT for five years.
Your background risk first. Around 1 in 16 women who never use HRT are diagnosed with breast cancer between 50 and 69. That is 63 cases per 1,000 women. This is the number every other number below should be read against.
Ten years of use roughly doubles those extra cases. Under a year of use carries little or no increase.
Read that again with the 63 in mind. The most commonly quoted risk, the one that emptied the clinics, is around 20 extra cases on top of 63, for the highest-risk regimen, over five years. It is a real number. It is not the number a generation of women were led to imagine.
The oestrogen is not what drives most of the breast cancer risk. The progestogen is.
In the WHI's oestrogen-only arm, in women who had had a hysterectomy and therefore did not need a progestogen, breast cancer cases were lower than on placebo. Pooled observational data point the other way, at roughly five extra cases per 1,000 over five years. The two bodies of evidence genuinely disagree on the direction, which is worth saying plainly rather than picking the flattering one.
What both agree on is the size: with oestrogen alone, the effect on breast cancer is small either way. That matters enormously for women who have had a hysterectomy, and it is why the phrase "HRT causes breast cancer" is doing at least three different jobs badly.
This is where even well-meaning articles go wrong, including, until now, this one.
For clots, the route matters a great deal. Oral oestrogen raises the risk of venous thromboembolism: roughly 11 extra cases per 10,000 women per year with oestrogen alone, and around 21 with combined. Oestrogen through the skin, as a patch or gel, does not appear to carry that increase, which is why it is generally the safer option, and markedly so for women who already have clot risk factors.
For breast cancer, the route does not appear to matter. The UK regulator's position is that systemic HRT is associated with the excess described above regardless of whether it is swallowed or absorbed through the skin.
So "patches are safer" is true and incomplete. Patches are safer for your veins. They are not a way around the breast cancer conversation, and anyone selling them that way is overselling.
The progestogen may matter as well: the type used in the 2002 trial is associated with more clot risk than others, and micronised progesterone is often preferred now. That is a conversation to have, not a settled fact to quote.
Vaginal oestrogen is not systemic HRT. The dose is tiny, absorption is minimal, and it is safe for the large majority of women, including many who cannot take systemic HRT at all. It transforms dryness, painful sex and recurrent urinary infections, and far too few women are offered it.
If dryness is your main problem, you may not need the bigger decision at all. See vaginal dryness and intimacy.
If your menopause came early, before 45, or your ovaries stopped before 40, this whole article applies differently to you.
You are not adding hormones on top of a normal midlife. You are replacing hormones your body expected to have for another decade, and your bones and blood vessels were counting on them. In that situation HRT is generally recommended until the usual age of menopause, and the risk comparison is against other women your age, not against a 60-year-old. See early menopause before 45 and surgical menopause.
An honest article names these rather than implying HRT suits everyone.
Current or past breast cancer, some other hormone-sensitive cancers, unexplained vaginal bleeding that has not been investigated, active liver disease, and a history of blood clots or stroke all change the calculation, some absolutely and some conditionally. Migraine with aura, high blood pressure and clot risk factors do not usually rule HRT out, but they do steer the route and the type.
The point of the list is not to frighten. It is that "is HRT safe" is the wrong question. "Is HRT reasonable for me, in what form" is the right one.
There is no arbitrary stopping date, and no age at which HRT is automatically withdrawn. UK guidance sets no fixed limit; the decision is a periodic review of whether the benefits still outweigh the risks for you.
Women are still told they must come off at five years, or at 60. That is not what the guidance says, and if you are told it, it is worth asking which guidance is being quoted.
HRT is neither the miracle nor the menace it's been painted as at different times. For many women with troublesome symptoms it is safe and life-changing; for some it isn't the right choice. What's changed is that the conversation can now be based on current evidence rather than a twenty-year-old headline.
What has not changed is the cost of that headline. A generation of women went through the transition without a treatment that would have returned their sleep and protected their bones, because a relative risk was printed where an absolute one belonged. Whatever you decide, decide it on the real numbers.
If symptoms are affecting your life, you deserve an up-to-date, individual discussion with a clinician who keeps current with the research, not a flat "you'll be fine" or a fearful "absolutely not." Armed with the real picture, that conversation is one you can lead.
Is HRT safe?
For many healthy women starting around menopause, the benefits tend to outweigh the risks, but it's an individual decision to make with your doctor. The honest version is a set of numbers rather than a yes or no.
When is the best time to start HRT?
Generally around the menopause transition, roughly under 60 or within ten years of your last period. Starting much later shifts the balance of benefit and risk.
Does HRT cause breast cancer?
Combined HRT is associated with a small increase: around 14 to 20 extra cases per 1,000 women over five years, against a background of 63 per 1,000. Oestrogen alone carries little or no increase, and the evidence disagrees on whether it raises or lowers it. Under a year of use carries little or none.
Are patches safer than tablets?
For blood clots, yes, and clearly so. For breast cancer, the route does not appear to change the risk. "Patches are safer" is true about your veins, not about everything.
Does HRT cause weight gain?
No. Pooled trial evidence found no effect on body weight beyond what women gain at menopause anyway, and no evidence that it prevents that gain either. See does HRT cause weight gain?
How long can I stay on HRT?
There is no fixed limit and no automatic stopping age. It is reviewed periodically rather than withdrawn on a schedule.
Sources: NICE NG23, Menopause: identification and management (2015, updated 2024) · Medicines and Healthcare products Regulatory Agency, Hormone replacement therapy: safety update, and the MHRA summary table of HRT risks and benefits per 1,000 women · Rossouw JE et al., Women's Health Initiative, risks and benefits of oestrogen plus progestin, JAMA 2002 · Collaborative Group on Hormonal Factors in Breast Cancer, Lancet · Figures are for women aged 50 to 69 in the UK and will differ for your own risk profile. Educational only, not medical advice.
Keep reading: Does HRT cause weight gain? · Hot flushes and night sweats: what helps · Protecting your bones at menopause · Vaginal dryness and intimacy · Our full guide to HRT · Take the free Hormone Quiz