Letrozole: Uses, Dosage, Side Effects

Reviewed byClearHormones Editorial Team, Medical-literature review

Last reviewed: 5/27/2026 · How we review →

Letrozole (Femara) is an aromatase inhibitor. In women's health it is first-line for ovulation induction in PCOS — it outperformed clomiphene for live birth rates in PCOS trials. Also used in breast cancer. Taken orally for 5 days early in the cycle for fertility use.

Quick facts

Drug class: Aromatase inhibitor
Brand names: Femara
Forms: Oral tablet (2.5 mg)

What clinical trials show(2)

Published trial outcomes; sources listed below.

PPCOS II (NEJM 2014). Letrozole produced higher live-birth rate (27.5%) vs clomiphene (19.1%) in PCOS (NCT00719186)
Cochrane ovulation-induction review. Letrozole improves live birth and ovulation rates vs clomiphene in PCOS

Go deeper(3)

Reference pages for this drug, built from FDA prescribing information.

Side effects →Incidence rates and management Dosage →Schedules, forms, missed doses Pregnancy →Pregnancy and breastfeeding guidance

Key drug interactions(2)

Top interactions by severity; always review your full medication list with a clinician or pharmacist.

Letrozole key drug interactions
Interacts with	Severity	Mechanism
Tamoxifen	moderate	Reduces letrozole plasma levels
Estrogen-containing products	moderate	Counteract letrozole's estrogen-lowering action

Pregnancy at a glance

Letrozole is used BEFORE pregnancy to induce ovulation — it is cleared from the body before conception occurs. It is not taken during an established pregnancy. Large studies showed no increase in birth defects vs clomiphene.

Full pregnancy and breastfeeding guide →

Telehealth providers that prescribe Letrozole(4)

Independently reviewed providers offering Letrozole for PCOS ovulation support. Editorial ranking — affiliate links don't affect order.

Allara
90/100
Comprehensive PCOS and hormonal health telehealth. Multidisciplinary care team including endocrinologists, dietitians, and mental health professionals.
Pollie (PCOS Specialist)
85/100
PCOS-focused platform with phenotype-driven treatment matching. Specialist providers only.
Pollie
77/100
PCOS-focused care platform combining clinician access with personalized supplement protocols. Subscription model with medication and supplement bundling.
Felix Health PCOS
77/100
Async PCOS prescribing for acne, hirsutism, and irregular cycles. Affordable monthly plans.

We don't sell Letrozole or any medication. These are editorial reviews of telehealth providers — clicking through may earn us a commission, which does not affect our scoring.

Sources(4)

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