MANY WOMEN BENEFIT from HRT (hormone replacement therapy) but, even in its bioidentical format, HRT is still a medicine – and like all medicines, there are potential side-effects. For most women, these side-effects are merely a temporary nuisance, but for others they can be severe.

This article was included in issue 107 (Winter 2025/26) of The Menopause Exchange newsletter.

Before starting any treatment, it’s important to be clear why you’re taking it. You’re usually taking HRT for menopausal symptoms, e.g. hot flushes, anxiety or mood changes, and symptom severity will dictate how much you want to stay on HRT. For example, if your symptoms are mild, even a few irritating side-effects may be worse than the symptoms themselves. Conversely, if your symptoms are severe, you may be willing to put up with some side-effects to get rid of your menopausal symptoms. The good news is that most side-effects are mild, often settle down after a few weeks and can be minimised by adjusting your treatment.

HRT hormones

HRT consists of two hormones: oestrogen, the main hormone that improves your symptoms; and progesterone (often called a progestogen), which is necessary for the protection of the lining of your uterus (womb). If you’ve had a hysterectomy, there’s no need for a progesterone. Both hormones may have side-effects, so it’s important to identify which component is likely to be the problem, as the hormones can be changed separately.

Oestrogen-related side effects

These side-effects are similar to the symptoms of early pregnancy, such as nausea, breast tenderness, leg cramps, bloating and headaches. These are usually dose-related and resolve within a few weeks. The best way to avoid getting them is to start with a low dose and build up gradually. This is particularly important if your periods stopped a while ago and you’ve not had any oestrogen for a few years. If side-effects persist, it may be necessary to reduce the dose or switch to a different preparation: for example, if you’re having nausea on a tablet, switching to a gel or patch may be better. Taking a tablet at night may also reduce nausea or bloating. Some women develop skin irritation with patches and gels, so a tablet might be more suitable.

Progesterone-related side-effects

These are usually the most troublesome part of HRT and are similar to premenstrual syndrome (PMS), causing fluid retention, breast tenderness, backache, depression, mood swings, irritability and headaches.

Progesterone is typically given cyclically (roughly two weeks on, two weeks off) when HRT is started in the perimenopause. In this scenario, the side-effects are usually only noted when the tablet is being taken, and they disappear when it isn’t being taken. If progesterone is given continuously, side-effects will probably be present all the time, but the doses are lower and there are no monthly hormonal fluctuations so they may not be so severe.

Many different types of progestogens are used in HRT, and the side-effects can often be reduced by changing to a different type. Micronised progesterone is the most popular type, but it can cause drowsiness, so women are usually advised to take it at night. Some women find that using the micronized progesterone tablet vaginally reduces the side-effects, but you should speak to your doctor before you do this, as the tablets aren’t licensed to be used vaginally.

Many HRT preparations have a fixed type and dose of oestrogen and progestogen, so it may be necessary to switch to a different product and even change the route of administration. Most of the progestogens used in HRT are also in hormonal contraceptives, so it can be helpful to remember which type you took and whether or not you got on with it. Most progestogens are in tablet form, but changing to a patch may be helpful. There’s also a coil containing progestogen (Mirena) that’s very effective for bleeding control and usually has very few side-effects.

A few women can’t tolerate progestogens at all. But as progesterone is such an important component of HRT, don’t stop it without discussing this with your doctor. You may need a referral to a specialist unit.

Bleeding

Irregular bleeding on HRT is very common and one of the main reasons women stop it. Perimenopausal women should be taking cyclical HRT (a 28-day cycle to mimic the menstrual cycle) and this should result in regular, predictable period-like bleeds. Postmenopausal women should have continuous combined or no-bleed HRT, when the progestogen is given continuously.

With all types of HRT, erratic breakthrough bleeding is common in the first three to six months. Quite often, the bleeding will settle with minor increases to the dose, but if there’s persistent irregular bleeding after six months of starting HRT, you’ll need further investigations to make sure there are no underlying problems. There are national guidelines, so if you get any bleeding that you’re not expecting, consult your doctor.

Testosterone

Although doses of testosterone added to HRT are small, side-effects can occur, such as increased facial or body hair, greasy skin, acne and male pattern baldness. Reducing the dose or stopping testosterone will usually see these side-effects settle down.

Rarer but more serious side-effects include deepening of the voice. This is irreversible so it’s important not to go above the prescribed dose. Regular blood tests are advised to make sure the testosterone levels aren’t too high.

Conclusion

While HRT side-effects are common, these are usually mild and temporary. If they’re troublesome, there are plenty of options to adjust the HRT to minimise them. Side-effects are rarely a reason to stop HRT, but it’s important not to lose sight of why you’re on the treatment.

About the author

Mr Tim Hillard is a consultant gynaecologist and menopause specialist at University Hospitals Dorset in Poole.

Created Winter 2025/26
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