HRT side effects and risks: what to expect
Short answer: Most side effects of HRT are mild and show up in the first months: tender breasts, headaches, feeling sick and unexpected bleeding. They usually settle within three months. The risks of blood clots, stroke and breast cancer are small and depend on the type of hormones, how you take them (tablet or through the skin), your age and how long you use them. Which balance is right for you is a conversation with your doctor.
What are the side effects of HRT?
HRT (hormone replacement therapy, also called menopausal hormone therapy) is usually oestrogen, with a progestogen added if you still have your womb. The NHS lists these side effects for each hormone:
- Oestrogen: headaches, breast pain or tenderness, unexpected vaginal bleeding or spotting, feeling sick, mood changes, leg cramps, a mild rash or itching, diarrhoea and hair loss.
- Progestogen: changes in bleeding, headaches, breast tenderness, feeling sick, feeling tired or dizzy, mood changes and acne.
- Patches, gel or spray: the same side effects, plus sometimes itching or red, sensitive skin where you apply it.
Dutch GP guidance (Thuisarts) adds that your body can hold on to more fluid in the first months, which explains the tender breasts, headaches and nausea. Not everyone gets side effects, and some of them look a lot like menopause symptoms themselves, so HRT is not always the cause. If you are unsure which is which, see all perimenopause symptoms at a glance.
How long do HRT side effects last?
Often a few weeks. The NHS advises staying on treatment for at least three months if you can, because side effects usually improve in that time. Relief follows a similar timeline: many women notice fewer hot flushes after two to three weeks, with the full effect from about three months. That is also when your first review usually happens.
If side effects stay, your doctor can change the dose, switch to a different hormone or change how you take it, for example from tablets to patches. Never change your dose on your own.
Does HRT cause weight gain?
There is little evidence that it does. The NHS says some weight gain is common during menopause and with age, whether or not you take HRT. Fluid retention in the first months can make you feel heavier for a while.
How big are the risks of HRT?
Small, but not zero. They differ by type of HRT, so it helps to look at them one by one:
| Risk | What the sources say |
|---|---|
| Breast cancer | For combined HRT (oestrogen plus progestogen) the NHS counts around 5 extra cases in every 1,000 women who take it for five years. The risk rises the longer you take it and falls after you stop. Oestrogen only HRT brings little or no increase. Thuisarts notes that with oestrogen plus progesterone or dydrogesterone for under five years, a higher risk is unlikely. |
| Blood clots | Tablets raise the risk slightly, though it stays very low. Patches, gels and sprays do not raise it, according to the NHS. |
| Stroke | Tablets raise the risk slightly. It stays very low, particularly under 60. Smoking, high blood pressure and high cholesterol matter far more. |
| Heart disease | The NHS finds little or no effect on coronary heart disease. Thuisarts mentions a slightly higher chance of a heart attack. |
| Womb cancer | Oestrogen on its own makes the womb lining grow. That is why a progestogen is added if you still have your womb. |
Risks grow with age and with longer use, and they fall again after you stop. Thuisarts puts it at about two years before your risk is back to that of someone who never took hormones. The Menopause Society, the North American body of menopause specialists, concludes that for healthy women under 60, or within ten years of their final period, the benefits of treating bothersome hot flushes usually outweigh the risks.
Are patches or gel safer than tablets?
For blood clots, yes. Hormones taken through the skin do not pass through the liver first, and the NHS finds no raised clot risk with patches, gels and sprays. Thuisarts describes the skin route as possibly safer if you are overweight or have high blood pressure, migraine or a higher risk of heart disease. Tablets, patches, gel and spray work equally well against hot flushes.
Vaginal oestrogen (a cream, tablet or ring for vaginal dryness) is a separate group. The dose is low and very little reaches the rest of your body. The NHS says it does not raise the risk of breast cancer or blood clots.
Who should not take HRT?
Thuisarts lists HRT as unsuitable if you:
- have or had a hormone sensitive cancer, such as breast or womb cancer
- have had a blood clot in a vein or lung (with blood thinners it is sometimes possible)
- have had a heart attack or stroke
- have vaginal bleeding with no known cause
- have liver disease
- smoke
If one of these applies to you, there are other treatments. Your doctor can go through them with you.
How long can you stay on HRT?
Guidance differs by country. Dutch GP guidance advises using it for no more than five years where possible, because risks rise with longer use. In every system the principle is the same: a review after about three months, then once a year, where you and your doctor weigh symptoms, side effects and risks and decide whether to continue. You can stop at any time after talking to your doctor. Stopping and restarting again and again is not a good idea.
When should you see a doctor?
- your side effects are severe or last longer than three months
- irregular bleeding or spotting does not go away, lasts beyond the first months or gets heavier
- you bleed after not having periods for more than a year
- you notice a change in your breast
- you have a swollen, painful lower leg or other signs of a blood clot: get help straight away
At a review it helps to show what you took and how you felt. In PERIOD. you log your HRT, your symptoms and any bleeding day by day. The app logs and shows, your doctor decides on treatment. Read how in tracking your HRT, and prepare with your GP appointment about menopause. More about this stage is on our menopause page.
Sources: NHS, Side effects of hormone replacement therapy (HRT) and Benefits and risks of hormone replacement therapy (HRT); Thuisarts.nl (Dutch College of General Practitioners), Ik wil misschien hormoontherapie tegen opvliegers in de overgang and Ik ga hormonen gebruiken in de overgang; The Menopause Society, 2022 Hormone Therapy Position Statement. This article is general information, not medical advice.
Frequently asked questions
What is the most common side effect of HRT?
Tender breasts, headaches, feeling sick and unexpected bleeding in the first months. They usually ease on their own. Keep a note of them and bring them up at your three month review.
Does HRT cause breast cancer?
Combined HRT raises the risk slightly, more so with longer use. The NHS counts around 5 extra cases in every 1,000 women who take it for five years, and the risk falls after stopping. Oestrogen only HRT brings little or no increase.
Is bleeding on HRT normal?
In the first months it is common. If unexpected bleeding continues, gets heavier, or starts after more than a year without periods, have it checked.
Can you stop HRT suddenly?
Talk to your doctor first. Dutch GP guidance says you can stop in one go without tapering. Symptoms can return, so plan it together.
Does HRT help prevent osteoporosis?
Yes. The NHS lists preventing osteoporosis as a benefit, alongside relief from hot flushes, sleep problems and vaginal dryness. It matters most if your periods stopped before 45.
Want your HRT and symptoms in one overview? Download PERIOD. on the App Store or Google Play.
