letrozole Side Effects

What the FAERS Data Reveals About letrozole Side Effects

The FDA Adverse Event Reporting System (FAERS) contains 59,013 voluntary reports linked to letrozole and its brand equivalents (Femara), spanning 2004 through 2025. Of those, 5,837 (9.9%) listed death as an outcome and 15,111 (25.6%) involved hospitalization. The most common indication reported alongside adverse events was Breast Cancer.

Demographic breakdowns help contextualize who is being exposed to the drug. Of reports with known sex, 98% were female and 2% male; age distribution skews toward 45-64, with 17,286 reports in that bracket. The single most reported reaction is fatigue with 7,159 submissions, followed by nausea and neutropenia.

FAERS is a signal-detection tool, not a scorecard. Reports are voluntary, and a single case may list multiple suspect drugs, so numbers above should not be read as incidence rates or per-patient risk. Widely prescribed drugs naturally accumulate more reports than niche therapies even when individual risk is low. These aggregates are useful for spotting patterns that merit further pharmacovigilance, not for choosing between medications. This page is for educational reference only and is not medical advice — speak with a licensed clinician about any side-effect concerns.