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Letrozole for breast cancer


Take one 2.5 mg letrozole tablet every day. Swallow the tablet with a drink of water.

The most common side-effects of treatment are hot flushes, sweating, joint pain, and feeling tired. These can occur in more than 1 in 10 women who take letrozole.

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About letrozole

Type of medicine

An aromatase inhibitor hormone antagonist

Used for

Breast cancer in women

Also called


Available as


Letrozole is a hormonal breast cancer treatment.

Some breast cancers need the hormone oestrogen to grow. In women who have been through the menopause, the main source of oestrogen is through the change of sex hormones, called androgens, into oestrogen. An enzyme called 'aromatase' is needed for this change to occur. Letrozole works by blocking (inhibiting) this enzyme. This reduces the amount of oestrogen in your body, which slows the growth of the cancer cells.

Before taking letrozole

Some medicines are not suitable for people with certain conditions, and sometimes a medicine can only be used if extra care is taken. For these reasons, before you start taking letrozole it is important that your doctor knows:

  • If you have not yet gone through the menopause, or if there is a possibility you could be pregnant.

  • If you have any problems with the way your liver works, or any problems with the way your kidneys work.

  • If you have a loss of bone density, or 'brittle bones' - a condition known as osteoporosis.

  • If you have ever had an allergic reaction to a medicine.

  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

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How to take letrozole

  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about letrozole and it will also provide you with a full list of the side-effects which you could experience from taking it.

  • Take one 2.5 mg tablet of letrozole each day, exactly as your doctor tells you to.

  • You can take letrozole at whatever time of day you find easiest to remember, but try to take your doses at the same time of day each day. This will help you to remember to take letrozole regularly.

  • Swallow the tablet with a drink of water. You can take letrozole either with or without food.

  • If you forget to take a dose at your usual time, take it as soon as you remember. If you do not remember until the following day, leave out the forgotten dose from the previous day and take the dose that is due as normal. Do not take two doses on the same day to make up for a missed dose.

  • Continue to take the tablets regularly each day until your doctor tells you otherwise. You may need to take letrozole for a number of years.

Getting the most from your treatment

  • Try to keep your regular appointments with your doctor and clinic. This is so your doctor can check on your progress. Letrozole lowers the levels of female hormones in your body, which can reduce the strength of your bones. You will need to have bone density tests to check for this before and during your treatment.

  • If you are due to have an operation or any dental treatment, tell the person carrying out the treatment that you are taking letrozole.

  • If you buy any medicines 'over the counter', check with a pharmacist that they are safe to take with your prescribed medicines.

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Can letrozole cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains the most common ones associated with letrozole. The best place to find a full list of the side-effects which can be associated with your medicine, is from the manufacturer's printed information leaflet supplied with the medicine. Alternatively, you can find an example of a manufacturer's information leaflet in the reference section below. Speak with your doctor or pharmacist if any of the following become troublesome.

Very common

letrozole side-effects

(these affect more than 1 in 10 women)

What can I do if I experience this?

Hot flushes, increased sweating

Try to keep cool by wearing light, airy clothes

Headache, muscle or joint pain

Drink plenty of water and ask a pharmacist to recommend a suitable painkiller. If it continues, let your doctor know

Feeling tired, weak or dizzy

Do not drive and do not use tools or machines while affected

High blood levels of cholesterol

Your doctor will arrange for you to have tests to check for this

If you experience other symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for further advice.

How to store letrozole

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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