Letrozole Treatment

Letrozole Treatment 

Patient Information

Fertility Fusion

• Author ID: EB / OO
• Leaflet ref: FF 004
• Version: 6
• Leaflet title: Letrozole Treatment
• Last review: October 2025
• Expiry Date: October 2027

Introduction

Letrozole (Femara) is a medication approved for the treatment of breast cancer. It is an aromatase inhibitor and works by lowering the production of Estrogen.  Letrozole has also been shown to be effective at inducing ovulation in infertility patients. 

Treatment may increase the chance of a twin pregnancy, although this is much less than with Clomiphene, where the risk can be increased by over four-fold. 

Benefits

The benefits of taking Letrozole tablets are to encourage or regulate ovulation to achieve a pregnancy. The half-life of Letrozole is very short (2 days) compared to Clomiphene. This means the medication is metabolized more rapidly and the side effects are less. Letrozole does not affect the cervical mucus or endometrial (womb) lining as much as Clomiphene. This is better for sperm transport in the cervix and a more favourable womb lining for implantation. 

Alternatives

Alternatives to Letrozole tablets are:

• Clomiphene tablets
• Gonadotrophin injections

Risks

• Ovarian hyperstimulation
• Increased risk of multiple pregnancy (approximately doubled)

Possible side effects:

• Hot flushes are most common. Other side effects are nausea, headaches, bloating, muscle aches, blurred vision and fatigue.  They can occur in approximately 10 to 20% of patients and are limited to that cycle.

If you experience problems with vision, pain or swelling in the abdomen or vomiting, the medication should be stopped and medical advice sought. Also, should you have any other questions or worries, please feel free to ring the ward and speak to a member of staff.

The starting dose is usually 2.5mgs daily. This medication is taken from day three, to day seven (5 days) of your menstrual cycle (period), day 1 being the first full day of bleeding.

You will be asked to attend for a blood test on day 21 of that cycle to check your progesterone level.  This hormone test will inform us whether you have ovulated or not.

Some patients with irregular periods may be asked to attend on different days of the cycle to try to determine whether ovulation has occurred.

It may take several days for the progesterone result to be available. Please telephone the nurses at the fertility centre for the result.  You will be advised to stay on the same dose of medication or to increase the dose if ovulation has not occurred.

If ovulation has occurred and you are not pregnant, in the next cycle you should take the same dose of Letrozole and ring the fertility centre on day 1 of your period for a scan, which will be done on or around days 8 to10. This will enable us to advise you more effectively when it is best to try for a pregnancy.

Before starting Letrozole treatment the doctor or nurse will discuss the drugs with you.  If you do not understand, or have any concerns, please contact the Fertility Centre for further advice.

Most patients will ovulate following treatment with one or two tablets of the Letrozole a day.  Some patients may require higher doses and others may not ovulate at all. Some patients may over respond to Letrozole where more than three follicles are produced at once. If this is identified at the scan around day 8 to 10 you will be advised to not have unprotected intercourse due to the increased risk of multiple pregnancy. 

Under these circumstances alternative treatments will be discussed.

Once ovulation has been confirmed it is usual to continue on the same dose for a total of six cycles.  If a pregnancy has not occurred after six ovulatory cycles, you will be asked to see the Consultant.

It is perfectly safe to take Letrozole for up to 12 months, although few pregnancies will occur after 4 to 6 months of treatment.

Contact telephone numbers

Fertility Fusion, Wrightington Hospital 

01257 256251 Monday to Friday 8am to 4:30pm

The Unit Counsellor can be contacted for support at any time, throughout your treatment and afterwards.  The telephone number is 01257 256251

Swinley Ward, Royal Albert Edward Infirmary 

Out of hours or in an emergency Telephone: 01942 822568

See also patient information leaflet REF: FF 010 Counselling Services - Fertility Fusion 

https://www.wwl.nhs.uk/leaflets/download/wwl-5feb49826d8015.89152671