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Side effects of tamoxifen

Find out about the side effects of the hormone therapy tamoxifen.

Tell your doctor or nurse if you have any side effects so they can help you manage them. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Common side effects

Each of these effects happens in more than 1 in 10 people (10%). You might have one or more of them.

Fluid build up may cause ankle and finger swelling or a puffy face. It can also cause weight gain.

This happens in about 1 in 10 people (10%).

You can get leg cramps. Walking may help to stretch the muscle and ease this.

You may have changes to your periods while you're on treatment. If you haven’t had your menopause your periods may become irregular. Some women find that their periods stop. They usually start again within 6 to12 months of treatment finishing.

However, for some women who are close to the time of their natural menopause they don’t start again.

Your hair may thin, this is usually not noticeable by other people but can be upsetting. It usually begins thinning out gradually within 3 to 4 weeks after you start taking the drug. 

Tips

  • Use gentle hair products such as baby shampoos.
  • Don't use perms or hair colours on thinning hair.
  • Use a soft baby brush and comb thinning hair gently.
  • Pat your hair dry gently rather than rubbing.
  • Avoid using hair dryers, curling tongs and curlers.

You might feel sick or be sick. Anti sickness injections and tablets can control it. Tell your doctor or nurse if you feel sick. You might need to try different anti sickness medicines to find one that works.

Tips 

  • Avoid eating or preparing food when you feel sick.
  • Avoid hot fried foods, fatty foods or foods with a strong smell.
  • Eat several small meals and snacks each day.
  • Relaxation techniques help control sickness for some people.
  • Ginger can help – try it as crystallised stem ginger, ginger tea or ginger ale.
  • Try fizzy drinks.
  • Sip high calorie drinks if you can’t eat.

Eye problems can occur, such as eyesight changes, cataracts or changes in the back of the eye (retina). If you notice any changes in your eyesight tell your doctor.

You might feel very tired during your treatment. It might take 6 months to a year for your energy levels to get back to normal after the treatment ends. A low red blood cell count will also make you feel tired.

You can do things to help yourself, including some gentle exercise. It’s important not to push yourself too hard. Try to eat a well balanced diet.

Talk to your doctor or nurse if you are finding the tiredness difficult to manage.

This affects about 1 out of 4 people (25%).

Your may have discharge from the vagina, dryness and itching. This affects about 1 in 10 (10%) women. Tell your doctor or nurse if you have any of these side effects.

Don't drive or operate machinery if you have this.

You can get hot flushes. You might also have other symptoms such as​:

  • reddening of the skin
  • sweating
  • a racing heart (palpitations)
  • feeling anxious, irritable or panicky

Tips to reduce hot flushes

  • Cut out coffee, tea and nicotine.
  • Cut down on alcohol.
  • Sip cold or iced drinks.
  • Wear layers of light clothing so you can take clothes off if you get too hot.
  • Have layers of bedclothes to remove as you need to.
  • Wear natural fibres such as silk or cotton instead of man made fabrics.

Talk to your doctor if your hot flushes are hard to cope with. They might be able to prescribe medicine.

Around 40 out of 100 people (40%) have moderate to severe hot flushes and sweats while taking tamoxifen and for some time afterwards.

A rash can also be itchy. Tell your doctor or nurse if you have a skin rash. They can prescribe medicine to stop the itching and soothe your skin.

Occasional side effects

Each of these effects happens in more than 1 in 100 people (1%). You might have one or more of them.

You may gain weight while having this treatment. You may be able to control it with diet and exercise. Tell your doctor or nurse if you are finding it difficult to control your weight. 

Let your doctor or nurse know if you have headaches. They can prescribe a mild painkiller such as paracetamol for you.

About 1 in 10 people (10%) have some change in their mood. Let your doctor or nurse know if you feel sad or depressed.

You may have bone pain and pain in the area of the tumour if you have advanced cancer. Tell your doctor or nurse as painkillers can help.

Rare side effects

Each of these effects happens in fewer than 1 in 100 people (1%). You might have one or more of them.

You might have an increase in symptoms after your first dose of this drug. This may carry on for a few weeks. This is called tumour flare. So your doctor might give you another type of hormone drug to prevent the symptoms of tumour flare. 

Symptoms of tumour flare include:

  • increased pain or difficulty passing urine
  • bone pain
  • back pain
  • blood in your urine
  • a feeling of pins and needles in your legs
Tell your doctor or nurse straight away if you have any of these side effects.

Very rarely it makes you feel sick, thirsty or constipated. These symptoms can be signs that the level of calcium in your blood has gone up. If you have any of these symptoms, tell your doctor or nurse.

Your risk of blood clots (thrombosis) can slightly increase when you take this drug. Tell your doctor if you or a close relative have had a blood clot in the past.

Let them know if you have pain, redness or swelling in your legs. Also tell them if you have sudden breathlessness, chest pain, or if you cough up blood.

You might have liver changes that are usually mild and unlikely to cause symptoms. They usually go back to normal when treatment finishes. You have regular blood tests to check for any changes in the levels of chemicals produced by the liver.

There is a very slight increased risk of developing a cancer of the womb. If you have any abnormal bleeding, or other symptoms that worry you, tell your doctor or nurse so that you can have a check up.

About tamoxifen

More information about this treatment

We haven't listed all the very rare side effects of this treatment. For further information see the electronic Medicines Compendium (eMC) website.

You can report any side effect you have that isn’t listed here to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Information and help

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