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Letrozole

Brand names: Femara

Letrozole lowers estrogen to treat hormone-sensitive breast cancer after menopause. It's also used off-label to help ovulation in PCOS.

Brand namesFemara
Type of medicineAromatase inhibitor
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

For fertility, it's taken for 5 days early in the cycle.

What it's used for

  • Hormone-receptor-positive breast cancer after menopause
  • Off-label: inducing ovulation, especially in PCOS

How to take it

  • Take it once a day at the same time, with or without food (or on cycle days 3 to 7 for fertility).

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Hot flashes
  • Joint pain
  • Tiredness
  • Bone thinning (long use)
Call 911Chest pain or signs of a stroke
Call your provider todayPain or swelling in one leg
Call your provider todayA broken bone from a minor fall

Warnings

  • Bone density and cholesterol are checked with long-term use.

Other medicines, foods, and alcohol

  • Tamoxifen lowers its level.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Not used during pregnancy. For fertility use, take a pregnancy test as directed before each cycle.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.