Letrozole (Femara®)

Take it as an alternative to clomiphene citrate (Clomid®).

Note: Take only after a negative pregnancy test.


It can be taken alone or with gonadotropins (injectable fertility medicines) to help ovulation.

Dose and route

It comes in 2.5 mg tablets. One to three tablets are taken at the same time by mouth on days 3 to 7 of the menstrual cycle. Your doctor will tell you what does to take. It absorbs quickly and totally from the gastrointestinal tract. It is not affected by food.


It works by interfering with how estrogen is made in the ovaries. This leads to stimulation of pituitary hormones (FSH and LH). FSH and LH stimulate oocyte (egg) maturation and ovulation.

It is not approved for fertility treatment at this time. It has been used for this purpose for many years though. It is approved for use in breast cancer prevention.

Adverse effects

Less than 5 out of 100 people will feel:

  • More tired than normal
  • Hot flashes
  • Nausea
  • Musculoskeletal pain
  • Painful breathing
  • Coughing

People often have fewer side effects with letrozole than with Clomid®. Check a urine pregnancy test at home, even if your period seems normal, before starting letrozole.

Start it after a normal period. Call your care team if your period is not a normal flow or comes at an unexpected time, before starting your medicine.

Birth defects

Letrozole is a pregnancy category D medicine. This means it should not be taken if you are pregnant.

It has a short half-life, and should be out of your system by the time you would be pregnant.

Studies show:

  • Compared to the general population, there is not a higher rate of birth defects after taking letrozole.
  • The rate of birth defects after letrozole use is not higher than after Clomid® (clomiphene) use.

Based on studies, we believe it to be a safe alternative to Clomid®.

Last reviewed: 
January 2021

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