Hormone replacement therapy (HRT): types, benefits and risks in real numbers

Hormone replacement therapy (HRT) replaces the estrogen the ovaries stop making at menopause, and it is the most effective treatment for hot flushes and night sweats ². For most women in their 50s the risks are small, and they depend heavily on whether the estrogen goes through the skin or the gut. Much of the fear traces back to a 2002 trial of one tablet in women whose average age was 63, and nearly two decades of follow-up since then has changed the picture. This guide gives the numbers to weigh with your clinician.

What hormone replacement therapy is

Hormone replacement therapy, also called menopausal hormone therapy (MHT) or estrogen replacement, is prescription estrogen given to replace what the ovaries stop making around menopause. Women who still have a womb also take a progestogen, a hormone that stops estrogen from overgrowing the womb lining. Some women add a small dose of testosterone for low sexual desire. HRT can start during perimenopause, the years of irregular periods before the final one, as well as after periods have stopped.

Men who search for HRT usually mean testosterone therapy, which is covered on the low testosterone page. Gender-affirming hormone therapy is a separate subject and is outside this guide.

What HRT helps with, and how soon

The North American Menopause Society (now The Menopause Society) reviewed the evidence in 2022 and put the main benefit plainly:

Hormone therapy remains the most effective treatment for vasomotor symptoms (VMS) and the genitourinary syndrome of menopause (GSM) and has been shown to prevent bone loss and fracture.The North American Menopause Society, 2022 Hormone Therapy Position Statement ²

Vasomotor symptoms are hot flushes and night sweats. Genitourinary syndrome of menopause is the vaginal dryness, painful sex and urinary urgency that follow the fall in estrogen. HRT also tends to help sleep broken by night sweats, low mood tied to the menopause transition, and joint aches. In the Women's Health Initiative (WHI) trial, combined HRT cut hip fractures from 15 to 10 per 10,000 women per year, about a third fewer ⁶; the osteoporosis page explains bone density scores.

HRT before and after: what changes, and when.

1. 12 to 4 weeksHot flushes and night sweats usually start to ease, and sleep often improves with them.
2. 2About 3 monthsHRT reaches its full effect on flushes and mood; this is when NICE suggests a first review of dose and side effects ¹.
3. 33 to 12 monthsVaginal dryness and urinary symptoms improve more slowly, and early side effects such as breast tenderness and spotting usually settle.
4. 4Years of useBone density is protected while HRT continues; the protection fades after HRT stops.

HRT does not reliably cause weight loss; it tends to shift where fat sits (less around the middle) rather than change the number on the scale. HRT is not recommended to prevent dementia ², and in the WHI memory study, starting combined HRT at 65 or older was linked to a higher risk of dementia ⁹.

The types of HRT: which hormones, which route, which pattern

Estrogen-only or combined

Estrogen-only HRT is for women who have had a hysterectomy. Women with a womb take combined HRT, because estrogen taken alone raises the risk of endometrial (womb lining) cancer ¹. The progestogen can be micronised progesterone (ground into very fine particles so it absorbs well), which is chemically identical to the body's own progesterone, or a synthetic progestin such as norethisterone or medroxyprogesterone. A hormonal coil (Mirena) can supply the progestogen inside the womb instead of as a pill.

Sequential or continuous

Sequential HRT gives estrogen every day and progestogen for 10 to 14 days a month, which produces a monthly bleed; it suits women still having periods or within 12 months of their last one. Continuous combined HRT gives both hormones every day and aims for no bleeding. For postmenopausal women, estrogen replacement is usually given as continuous combined HRT once 12 months have passed without a period, or as estrogen alone after a hysterectomy ¹.

Routes compared

The clot figures below come from a UK study of more than 80,000 women with blood clots: estrogen tablets were linked to a 58% higher risk of venous thromboembolism (a clot in a leg vein or the lungs), and estrogen through the skin, called transdermal, showed no increase ⁴. Among tablets, combinations using conjugated equine estrogens (made from horse urine) with medroxyprogesterone carried the highest risk. A separate UK study found standard-dose patches were not linked to more strokes, while tablets and higher-dose patches were ¹⁰.

Body-identical versus compounded bioidentical

Body-identical HRT means licensed estradiol and micronised progesterone, the same molecules the ovaries make, made to regulated, batch-tested standards. Compounded bioidentical hormones are custom mixes made by a pharmacy, often marketed with saliva or blood tests to set the dose. These mixes are not FDA approved and are not batch tested for strength, and a 2020 National Academies of Sciences, Engineering, and Medicine review, The Clinical Utility of Compounded Bioidentical Hormone Therapy, found too little evidence of safety or benefit to support their routine use ⁸. Both are called bioidentical; only the licensed products have trial data behind them.

Is HRT safe? The risks in real numbers

The WHI combined trial was stopped early in 2002 (results published that July) after it found more breast cancers in women taking conjugated equine estrogens (CEE, made from pregnant horses' urine) with medroxyprogesterone acetate (MPA, a synthetic progestin) than in women on placebo ⁶. The participants averaged 63, many were more than 10 years past menopause, and every woman took the same oral product. The table shows what the trial found per 10,000 women per year.

Put another way, 10,000 women on that tablet for a year had about 8 extra breast cancers, which is under 1 in 1,000 ⁶. When researchers tracked the WHI women for 18 years, they found no rise in deaths:

Among postmenopausal women, hormone therapy with CEE plus MPA for a median of 5.6 years or with CEE alone for a median of 7.2 years was not associated with risk of all-cause, cardiovascular, or cancer mortality during a cumulative follow-up of 18 years.Manson JE et al., JAMA 2017 ⁵

Analyses by age at the start of HRT support the timing hypothesis: HRT started under 60 or within 10 years of menopause is linked to a lower heart risk than HRT started later, when artery disease may already be established ². On 10 November 2025 the US FDA announced label changes to remove the boxed warning about heart disease, breast cancer and probable dementia from menopausal hormone therapy, while keeping the boxed warning about endometrial cancer for estrogen-only products ⁷.

Breast cancer by type and years of use

The largest analysis, from the Collaborative Group on Hormonal Factors in Breast Cancer, pooled data from 58 studies ³. For women of average weight who start HRT at 50 and take it for 5 years, the extra breast cancers by age 69 look like this:

In the same analysis, 10 years of HRT roughly doubled those extra cases, use for under a year added little, and some excess risk persisted for more than a decade after stopping in women who had used HRT for over 5 years ³. Drinking alcohol and excess weight after menopause also raise breast cancer risk. Whatever you decide, keep up routine breast screening (mammograms) and tell your clinician about any family history of breast cancer, since that can change the advice.

Who should not take HRT, or needs a specialist first

• Current or past breast cancer, or another estrogen-sensitive cancer
• Unexplained vaginal bleeding that has not been investigated
• A current or past blood clot or stroke (estrogen through the skin may still be possible with specialist advice)
• A heart attack or angina, current or recent
• Active liver disease with abnormal liver tests
• Untreated high blood pressure
• Pregnancy, which is possible in perimenopause

Women with migraine with aura, a BMI over 30, a known clotting tendency or high triglycerides are usually steered to patches or gels rather than tablets. The clotting tests guide explains what a clotting screen measures.

Starting HRT: what happens at the appointment

NICE says women over 45 with typical symptoms do not need a blood test to diagnose perimenopause or menopause; testing FSH (follicle stimulating hormone, which rises as the ovaries wind down) is kept for women aged 40 to 45 with symptoms and for women under 40 ¹. The clinician asks about your bleeding pattern, any personal or family history of clots and breast cancer, and migraine, and checks blood pressure. You start a dose, review it at about 3 months, then once a year ¹. Dose and route can change at any review, and many women move to a lower dose or the skin route as they get older. A routine hormone panel before HRT is not required; the female hormone panel guide explains what one shows if you have had it.

Questions worth bringing:

• Do I need combined HRT, and would micronised progesterone or a coil suit me?
• Given my history, is a patch or gel safer for me than a tablet?
• Should I be on a sequential or continuous regimen?
• What bleeding should I expect, and when should I report it?
• When will we review whether HRT is working?

Side effects, and what to do about them

The common early side effects of HRT are breast tenderness, bloating, headaches, nausea and irregular spotting, and most settle within 3 to 6 months. Progestogen intolerance (low mood, irritability or PMS-like symptoms in the progestogen phase) is the most common reason women stop; switching to micronised progesterone or a hormonal coil often helps, and that switch is a decision to make with the prescriber. Trials have not shown that HRT causes weight gain; weight tends to rise around menopause whether or not a woman takes HRT ². For mood changes that persist, the mood swings page covers other causes worth ruling out.

Testosterone for women

The only evidence-based reason to give testosterone to women is low sexual desire that causes distress after menopause, once estrogen is optimised ¹²; NICE supports considering it in that situation ¹. Testosterone for women is used at a much lower dose than men use, is not licensed for women in the UK, and has no FDA-approved product for women in the US. Clinicians check total testosterone and SHBG before starting and during treatment, to keep levels within the normal female range. The low libido page covers the other causes of low desire.

CalculatorFree testosterone calculatorEstimates how much testosterone is unbound and active from your total testosterone and SHBG, which matters more on oral estrogen.Work it out

How HRT changes your blood results

Estrogen tablets pass through the liver first, so they change blood results far more than patches or gels do. Oral estrogen raises SHBG, triglycerides and HDL cholesterol, and lowers LDL cholesterol and Lp(a) (lipoprotein(a), an inherited cholesterol particle linked to heart risk). It also raises thyroxine-binding globulin, the protein that carries thyroid hormone, so women on levothyroxine can need a dose change after starting estrogen tablets ¹¹; in that study the extra need showed up within about 12 weeks, so the prescriber usually rechecks TSH (thyroid stimulating hormone) in the first few months and decides whether to adjust it. The thyroid panel guide explains the result. FSH is not a useful guide once HRT has started, and estradiol does not usually need routine measurement in women doing well on HRT; symptoms, not a target level, guide the dose.

If your triglycerides are already high, the lipid panel guide explains the numbers, and a high reading is one reason clinicians favour transdermal estrogen.

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How long you can stay on HRT, and coming off

HRT has no fixed time limit. NICE and The Menopause Society advise a yearly review of benefits and risks, and many women continue past 60, often on a patch or gel ^{1 2}. Tapering HRT can make symptoms return more gently in the short term, but tapering and stopping at once give similar results after a few months, and symptoms come back for many women either way ¹. When and how to stop is worth planning with the prescriber. Bone protection fades within a few years of stopping, so bone health is worth discussing at that point; the bone markers guide explains the tests.

If HRT is not for you

Non-hormonal prescription options a clinician may discuss for hot flushes include, often off-label, some SSRI and SNRI antidepressants (medicines that act on the brain chemicals serotonin and noradrenaline, used here at low doses) and gabapentin ¹, and fezolinetant, a newer drug approved in the US in 2023 that blocks the brain receptor (NK3) that sets off flushes. Cognitive behavioural therapy has trial evidence for reducing how much flushes bother women and for menopause-related sleep problems ¹. Vaginal moisturisers and lubricants help dryness. St John's wort interacts with many medicines, including blood thinners and the contraceptive pill, and black cohosh has been linked to rare liver injury, so both are worth raising with a pharmacist before use.

Bone basics without hormones

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Mixed evidenceCalciumBone needs enough of it; trials favour getting most from food, with supplements filling a shortfall.In our shop

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