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Side effects of anastrozole (Arimidex)

Find out about the side effects of the cancer treatment drug anastrozole.

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.

The side effects may be different if you are having anastrozole with other cancer treatments.

Common side effects

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

Let your doctor or nurse know if you have headaches. They can give you painkillers such as paracetamol to help.

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.

Feeling sick is usually mild. Anti sickness tablets can control it if you need them. Tell your doctor or nurse if you feel sick. 

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.

Painful or stiff joints happen in more than 3 out of 10 women (30%).

You can get swollen joints while on this treatment. Let your doctor or nurse know.

Tiredness or fatigue happens in up to 2 out of 10 women (20%).

Loss of bone strength is caused by a lack of oestrogen over a long period of time. The bones are more likely to break. You might have a DEXA scan to check your bone density before you start treatment.

Mood changes happen in up to 2 in 10 women (20%).

You may have a loss of interest in sex known as a reduced libido. 

This occurs in more than 1 out of 10 women (10%).

Occasional side effects

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

Tell your doctor or nurse if you have diarrhoea. They can prescribe medicine to help you. 

Drink at least 2.5 litres of fluid a day. This helps to keep you hydrated.

Ask your nurse about soothing creams to apply around your back passage (rectum). The skin in that area can get very sore and even break if you have severe diarrhoea.

Contact your doctor or nurse immediately if you have diarrhoea 4 or more times a day, or any diarrhoea at night.

This drug can cause vaginal dryness. You can get vaginal moisturisers (lubricants) from your nurse or from the pharmacist.

Vaginal bleeding

This drug can cause vaginal bleeding. This mainly happens in the first few weeks of treatment. Tell your doctor or nurse if the bleeding continues.

Your hair may thin. This is usually not noticeable by other people but can be upsetting. Your hair should start to thicken up again within a few weeks of finishing treatment.


  • 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 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.

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


  • Avoid eating or preparing food when you feel sick.
  • Avoid fried foods, fatty foods or foods with a strong smell.
  • Drink plenty of liquid to stop you from getting dehydrated.
  • Relaxation techniques help control sickness for some people.
  • Ginger can help – try it as crystallised stem ginger, ginger tea or ginger ale.
  • Fizzy drinks help some people when they are feeling sick.

Carpal tunnel syndrome is when you have pain in your hands and you have a weak grip. You also feel numbness and tingling in your hands. Let your doctor or nurse know if you have this.

You might lose your appetite for various reasons when you are having cancer treatment. Sickness, taste changes or tiredness can all put you off food and drinks.


  • Eating several small meals and snacks throughout the day can be easier to manage.
  • Ask your doctor or nurse to recommend high calorie drinks to sip between treatments, if you are worried about losing weight.
  • You can make up calories between treatments for the days when you really don’t feel like eating.
  • Drink plenty of fluids even if you can't eat.
  • Don't fill your stomach with a large amount of liquid before eating.
  • Try to eat high calorie foods to keep your weight up.

You can have raised cholesterol levels in the blood. This is usually only slightly raised and you will have regular blood tests to check the levels.

This drug can make you feel sleepy. Make sure you rest.

Your nurse can give you painkillers for this.

Rare side effects

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

Inflammation of the liver (hepatitis) may be picked up on blood tests before symptoms develop. Symptoms include: 

  • a high temperature (fever)
  • joint and muscle pain
  • feeling more tired than usual
  • pain in the tummy (abdomen)
  • dark urine
  • pale, grey coloured poo
  • yellowing of the skin and eyes (jaundice)
Tell your doctor if you have any of the above symptoms, or have any new, persistent or worsening symptoms.

Trigger finger is when the finger or thumb is fixed in a bent position. Tel your doctor or nurse if you notice this.

About anastrozole

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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