Side effects of hormone replacement therapy (HRT) - NHS

Tier 1: Established: peer-reviewed research or government health authority
Publisher: NHS (National Health Service, UK) · Published: September 16, 2026 · Accessed: September 16, 2026

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• Like any medicine, the hormones used in HRT can cause side effects, but it's common to have no side effects or only mild ones; any side effects usually improve over time, so it's a good idea to carry on with treatment for at least 3 months if possible.
• HRT side effects can be similar to menopause symptoms, so it might not be the HRT causing them; it can take time to find the right dose and type, and a GP might suggest changing the dose, the type of HRT, or how it is taken (for example, switching from tablets to patches).
• Common oestrogen side effects include headaches, breast pain or tenderness, unexpected vaginal bleeding or spotting, nausea, mood changes including low mood or depression, leg cramps, mild rash or itching, diarrhoea, and hair loss; they will often go away after a few weeks.
• Common progestogen side effects include changes in periods including spotting or bleeding between periods, headaches, breast pain or tenderness, nausea, diarrhoea, tiredness or dizziness, mood changes including low mood or depression, mild rash or itchy skin, and acne; as with oestrogen, these usually go away after a few weeks.
• Irregular vaginal bleeding or spotting is common in the first few months after starting HRT and usually settles within 6 months; it is not usually a sign of anything serious.
• NHS advises speaking to a GP if side effects are severe or continue for longer than 3 months, or if irregular vaginal bleeding lasts more than 6 months after starting HRT, the bleeding becomes heavier, or bleeding occurs after a period of no periods.
• There's little evidence that most types of HRT cause weight gain; weight gain around menopause often happens whether or not HRT is taken.