Like all medicines, oestrogen can cause side effects. But it's common to have no side effects or only minor ones.
Side effects often improve as your body gets used to the medicine.
If you're also taking a progestogen medicine, some side effects may be caused by the progestogen. Check the leaflets that come with both your medicines.
Common side effects
These common side effects of oestrogen happen in more than 1 in 100 people. There are things you can do to help cope with them.
Headaches
Headaches usually only last for a few days after you start taking oestrogen as your body gets used to the medicine. Ask your pharmacist to recommend a painkiller. Talk to your GP if the headaches last longer than 1 week or are severe.
Breast pain or tenderness
This usually improves after a few weeks as your body gets used to the medicine. Talk to your GP if it bothers you or does not go away.
If you ever notice a lump or changes in your breasts, see your GP.
Unexpected vaginal bleeding or spotting
Unless you've had a hysterectomy to remove your womb, vaginal bleeding or spotting is common for the first 3 to 6 months after starting HRT. It usually settles down after this.
Talk to your GP if:
- you get heavy bleeding or unexpected bleeding after you've been taking HRT for 6 months
you've had a hysterectomy and you get any vaginal bleeding
Feeling sick (nausea)
If you're taking oestrogen tablets, try taking them with food. Stick to simple meals and do not eat rich or spicy foods.
This side effect should wear off after a few days as your body gets used to the medicine. If it lasts more than a week, talk to your GP. You may need to change your dose or switch to a different type of HRT.
Mood changes, including low mood or depression
This may last for the first few months as your body gets used to the medicine.
If it lasts longer than this or becomes too difficult to cope with, talk to your GP. You may need to change your dose or switch to a different type of HRT.
Mild rash or itching
If this covers a large area of skin it will usually only last for about a week as your body gets used to the medicine. Ask your pharmacist to recommend an antihistamine.
If it does not go away after about a week, talk to your GP. You may need a different treatment.
If you're using patches, gel or spray and the rash or itchiness is only affecting the area where you're putting the oestrogen, talk to your GP. You may need a different treatment.
Diarrhoea
Drink lots of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
If the diarrhoea lasts more than a week, talk to your GP. You may need to try reducing your dose or changing to a different type of HRT.
Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or GP.
Hair loss
If you have hair loss this may not always be caused by taking oestrogen, as it's sometimes a symptom of the menopause. If it worries you, talk to your GP.
Stomach pain
It can help to eat and drink slowly and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. Try to rest and relax. If you are in a lot of pain, talk to a pharmacist or GP.
Weight gain or loss
HRT can cause weight changes (up or down). But it's also common to put on or lose weight around the time of the menopause and as you get older. This means it might not be your medicine that's causing it. Eating a healthy, balanced diet and regular exercise will help you keep to a healthy weight.
Bloating
Try to avoid any foods that may make your symptoms worse like lentils, peas, beans and onions.
It might also help to:
- eat smaller and more frequent meals
- eat and drink slowly
- exercise regularly
Some pharmacy remedies help with bloating and wind. Ask your pharmacist for advice.
Leg cramps
Leg cramps are very rare, affecting less than 1 in every 1000 women.
Leg cramps usually only last for the first few weeks after you start taking oestrogen. Stretching your calf muscles regularly and gentle exercise may help prevent it.
If you keep getting leg cramps after the first few months of taking oestrogen, talk to your GP. You may need a different treatment.
Talk to a pharmacist or GP if the advice on how to cope does not help and a side effect is still bothering you.
Serious side effects
Serious side effects from oestrogen are rare.
Urgent advice: Call a doctor or call 112 or 999 for advice now if:
- you have pain, redness or swelling in one of your legs, usually in your calf
This could be a sign of deep vein thrombosis (DVT).
Non-urgent advice: Contact your GP if you have:
- a lump or changes in your breasts, especially dimpling of the skin, changes in the nipple or any lumps you can see or feel - this could be a sign of breast cancer
- any changes in vaginal bleeding after you have been taking oestrogen for more than a few months - this could be a sign of womb cancer
While you're taking HRT it's important to attend your breast screening appointments.
Emergency action required: Call 112 or 999 or go to the nearest emergency department (ED) now if you have any of the following symptoms:
- pain in your chest and breathlessness - this could be a sign of a blood clot in your lungs (pulmonary embolism) or heart problems
- difficulty speaking or moving your arm or leg, or a change in vision - this could be a sign of a stroke
- headache, tiredness or dizziness - this may be a sign of a big rise in your blood pressure
- yellow skin, dark pee and tiredness - these can be signs of liver problems
- migraine-like headache for the first time
Do not drive to the ED. Ask someone to drive you or call 112 or 999 and ask for an ambulance.
Bring all the medicines you take with you.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to oestrogen.
Urgent advice: Call 112 or 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Do not drive yourself to the emergency department.
The person you speak to at 112 or 999 will give you advice about what to do.
Other side effects
These are not all the side effects of oestrogen tablets, patches, gel and spray. For a full list see the leaflet inside your medicines packet.
Non-urgent advice: Find your patient information leaflet
Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.
Report side effects
You can report any suspected side effects to the Health Products Regulatory Authority (HPRA): report an issue - hpra.ie