Sounds like 'let-ro-zole'

Key points about letrozole

  • Letrozole is used to treat some types of breast cancer.
  • Letrozole is commonly called Letrole.
  • Find out how to take it safely and possible side effects.
blue unaunahi tile generic
Print this page

Letrozole is used to treat breast cancer in women who have gone through menopause. This type of breast cancer is called oestrogen receptor-positive breast cancer (cancer that grows in response to the hormone oestrogen). Letrozole belongs to a group of medicines called aromatase inhibitors.

After menopause, your ovaries no longer produce oestrogen but it is still made at low levels in fat and other tissues. This happens when an enzyme called aromatase changes other hormones into oestrogen through a complex process. Aromatase inhibitors are a type of medicine that block this process and reduce the amount of oestrogen in the body. In this way letrozole slows or stops the growth of the cancer cells. Read more about aromatase inhibitors.

In Aotearoa New Zealand letrozole is available as tablets (2.5 mg).

  • The usual dose of letrozole is 1 tablet once a day.
  • Letrozole is a long-term treatment so you may have to take it for several years.
  • Always take letrozole exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

  • Take letrozole at the same time each day, either in the morning or the evening. 
  • You can take letrozole with or without food.
  • If you forget to take your dose, take it as soon as you remember. But if it's nearly time for your next dose, just take the next dose at the right time. Don't take double the dose.
  • Don't stop taking letrozole suddenly; talk to your doctor before stopping.

Here are some things to know when you're taking letrozole. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Letrozole can make you drowsy, especially when you first start taking it. Avoid driving and doing other tasks where you need to be alert until you know how this medicine affects you. If it makes you drowsy, it's best to take it at bedtime. Limit alcohol intake, this can make drowsiness worse.
  • Letrozole can interact with some other medicines and herbal supplements, so check with your doctor or pharmacist before starting letrozole and before starting any new products.
  • Aromatase inhibitors, such as letrozole, may decrease bone mineral density (BMD) if you have been through menopause. This means you have a possible increased risk of fractures. You can help to keep your bones strong by regular weight-bearing exercise, eating a healthy diet rich in calcium and vitamin D and not smoking. If you are concerned, talk to your doctor about your risk. 

Like all medicines, letrozole can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Hot flushes and sweats

These are quite common when you're taking letrozole and are often mild, but this can vary. Hot flushes and sweats may improve after the first few months. You can try to reduce this effect by not smoking, reducing alcohol and avoiding hot drinks containing caffeine, eg, tea and coffee. Try to dress in layers, so you can remove clothes as needed, and wear clothes made from natural fabrics, such as cotton. If hot flushes are troubling you, tell your healthcare provider. There are some medicines that can help to reduce flushes.

Other side effects

Side effects What should I do?
  • Nausea (feeling sick) or vomiting (being sick)
  • Constipation or diarrhoea (runny poos)
  • Try taking letrozole with food or just before bed.
  • Tell your doctor if these side effects bother you.
  • Changes in appetite
  • Thinning hair
  • Joint pain, stiffness 
  • Feeling tired, or dizzy or have lack of energy 
  • Headache
  • Low mood
  • These may improve with time. 
  • Tell your doctor if they bother you.
  • Avoid driving if you feel tired or dizzy.
  • Vaginal bleeding 
  • Swollen legs or feet
  • Tingling in the arms or hands
  • Tell your doctor immediately or ring HealthLine 0800 611 116.
Did you know that you can report a medicine side effect to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product.(external link)


  1. Letrozole(external link) New Zealand Formulary

Free helplines

Healthline logo

Text 1737 Helpline logo

Logo with link to Māori Pharmacists website

Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

Last reviewed:

Page last updated: